On Sun, 27 Jun 2004 02:58:26 -0400, Gary Coffman
wrote:

On Fri, 18 Jun 2004 16:34:00 GMT, Seppo Renfors wrote:
Gary Coffman wrote:
If they did open atmospheric casting (and I'd strongly contend they
didn't have the technology to do any other kind, nobody did until the
latter half of the 19th century, and then only as a laboratory curiosity),
the resulting copper wouldn't be suitable for cold work, too much
porosity.

I agree that is most likely to have been the procedure. On the other
hand what we don't really know is if the porosity was a problem for
them.

It would be a problem, a big problem.

If they did attempt to salvage copper scraps, they likely *hammer
welded* them. That's done at temperatures below the melting point
of copper, so porosity doesn't become as serious a problem.

....and it would also eliminate porosity, would it not? So the small
bit could well be melted and cast into a small ingot - to later
"hammer weld" the porosity out of it.

No, it couldn't. Porosity isn't just little bubbles in the metal. Those
bubbles contain air, and at molten temperatures, the oxygen in that
air would oxidize the inside of the bubble. So what you wind up with is
a mass of copper with a lot of oxidized holes in it. You can't weld
copper that is oxidized. If this happens when a modern TIG welder
is welding copper (gas shield failure), the only thing he can do is
grind out all the porosity and start over.

You need to understand that copper behaves *differently* from silver,
gold, or even iron. Those metals respond well to casting techniques.
Nearly pure copper does not.

I'm aware of the difficulty - as well as the evidence it provides of
casting. As such evidence does exist, even if not widely, it indicates
the ability to melt copper.

No trick to melting copper. Doing something intelligent with the molten
metal in an atmospheric environment is a different matter. As I noted
previously, casting pure copper is difficult, even today.

But the question is, how pure was the copper.

In any case, copper can mostly by prevented from oxidising by melting
it under a layer of crushed coal or charcoal. In fact this method was
used for the production of largely deoxised (tough-pitch) copper in
recent time.

For a people
without inert gas shielded continuous casting furnaces, it would be
nothing but frustration.


Don't under rate the cunning of anceint man.



Eric Stevens

On Sun, 27 Jun 2004 03:11:14 -0400, Gary Coffman
wrote:

On Sat, 26 Jun 2004 11:13:49 +1200, Eric Stevens wrote:
On Wed, 23 Jun 2004 23:46:01 -0500, Tom McDonald
wrote:
In the case of the copper artifacts in the upper Great Lakes
area, all of the shapes and structures have been shown to have
been made via cold and hot-working techniques.

This is not my understanding. Metallurgical examination has shown that
some of the artifacts have been cast.

The evidence brought out in this thread is that *one* copper artifact
shows radiographic evidence (characteristic porosity) for part of it
being heated above the melting point in atmosphere at some point.
That is in no way conclusive evidence of casting technology. The
piece may have been an attempt at casting, or it may simply have
been overheated while being worked.

Maybe you missed it but http://www.iwaynet.com/~wdc/copper.htm was
cited a few weeks ago in sci.archaeology and introduces evidence for
the casting of copper. Arlington Mallery's book gives more details
including the results of competent metallurgical examination.



Eric Stevens

On Sun, 27 Jun 2004 03:03:50 -0400, Gary Coffman
wrote:

On Wed, 23 Jun 2004 23:46:01 -0500, Tom McDonald wrote:
Eric Stevens wrote:
On Fri, 11 Jun 2004 22:57:04 GMT, (Gary Coffman)
wrote:
But that said, casting pure copper is a bitch.


This from the guy who has just written that the task can be undertaken
by low-skilled workers?

Eric, I read that to mean that casting, in general (as with
iron, silver, bronze, gold, etc.) can be done by folks with
fewer skills than smiths. However, copper appears to present
particular problems with casting that are not so pronounced with
other metals, and which require higher skill levels than would
be required by those who cast other metals.

Exactly, and further, skill alone isn't sufficient to make sound
castings of pure copper. The proper equipment is also required.
Specifically, an inert atmosphere furnace. That technology
didn't exist until the late 19th century.

Just as well the ancient egyptians didn't know that they couldn't do
what they were doing. :-)



Eric Stevens

On Mon, 28 Jun 2004 09:04:49 +1200, Eric Stevens wrote:
On Sun, 27 Jun 2004 03:03:50 -0400, Gary Coffman
wrote:
On Wed, 23 Jun 2004 23:46:01 -0500, Tom McDonald wrote:
Eric Stevens wrote:
On Fri, 11 Jun 2004 22:57:04 GMT, (Gary Coffman)
wrote:
But that said, casting pure copper is a bitch.


This from the guy who has just written that the task can be undertaken
by low-skilled workers?

Eric, I read that to mean that casting, in general (as with
iron, silver, bronze, gold, etc.) can be done by folks with
fewer skills than smiths. However, copper appears to present
particular problems with casting that are not so pronounced with
other metals, and which require higher skill levels than would
be required by those who cast other metals.

Exactly, and further, skill alone isn't sufficient to make sound
castings of pure copper. The proper equipment is also required.
Specifically, an inert atmosphere furnace. That technology
didn't exist until the late 19th century.

Just as well the ancient egyptians didn't know that they couldn't do
what they were doing. :-)

So, are you claiming to have evidence that the ancient Egyptians
successfully cast pure native copper?

The metallurgical references I have say that native copper was
extremely rare in Egypt. Almost all of the copper they had was
refined from ores (smelted), and the results were *not* pure
copper. Rather, they were alloys, whether intentional or not,
of copper, arsenic, zinc, iron, or tin. These alloys behave *very*
differently from pure native copper when casting is attempted.

Gary

On Mon, 28 Jun 2004 09:04:48 +1200, Eric Stevens wrote:
On Sun, 27 Jun 2004 03:11:14 -0400, Gary Coffman
wrote:

On Sat, 26 Jun 2004 11:13:49 +1200, Eric Stevens wrote:
On Wed, 23 Jun 2004 23:46:01 -0500, Tom McDonald
wrote:
In the case of the copper artifacts in the upper Great Lakes
area, all of the shapes and structures have been shown to have
been made via cold and hot-working techniques.

This is not my understanding. Metallurgical examination has shown that
some of the artifacts have been cast.

The evidence brought out in this thread is that *one* copper artifact
shows radiographic evidence (characteristic porosity) for part of it
being heated above the melting point in atmosphere at some point.
That is in no way conclusive evidence of casting technology. The
piece may have been an attempt at casting, or it may simply have
been overheated while being worked.

Maybe you missed it but http://www.iwaynet.com/~wdc/copper.htm was
cited a few weeks ago in sci.archaeology and introduces evidence for
the casting of copper. Arlington Mallery's book gives more details
including the results of competent metallurgical examination.

No, I didn't miss it. That's where the reference to artifact R666 was
found. None of the other artifacts shown present convincing evidence
(characteristic porosity) of having been poured in atmosphere.

Gary

On Sun, 27 Jun 2004 14:59:04 -0500, Tom McDonald wrote:
Gary Coffman wrote:
On Sun, 27 Jun 2004 13:18:58 -0500, Tom McDonald wrote:
Gary Coffman wrote:
The evidence brought out in this thread is that *one* copper artifact
shows radiographic evidence (characteristic porosity) for part of it
being heated above the melting point in atmosphere at some point.
That is in no way conclusive evidence of casting technology. The
piece may have been an attempt at casting, or it may simply have
been overheated while being worked.

Are you referring to the sort of amorphous, three-cornered blob
listed in Conner's web site as 'R666', and in the Milwaukee
Public Museum (where it's curated) as '55786':

http://www.iwaynet.net/~wdc/copper.htm

If so, I have found additional information about that piece.

Yes, that's the one. What have you learned?

I corresponded with Dr. Alex Barker of the Milwaukee Public
Museum about this artifact, since they are curating it there.
His response about the description of the artifact was as follows:

"As to why one might wonder if it had been cast, it's relatively
dense for its size, and one surface is fairly smooth and
rounded--not like the upper surface of cast metal, however, but
one might perhaps imagine it as the bottom of an irregular
puddle of metal."

Interesting that he'd characterize it as "relatively dense for its size".
The density measurement reported on the web site says it is less
dense than ordinary native copper (8.2 vs 8.9). That's consistent
with the porosity shown in the radiograph.

I suspect that Dr Barker has neither metallurgical nor geological
training. So his density report is just that of a layman picking up
a hunk of metal. But if I'm wrong in that supposition, then he is
contradicting the information provided on the web site.

The description he gave seems to fit the photo on Connor's
site. It doesn't look like any purpose-made artifact; but it
does look as one might expect a bit of accidentally melted
copper to look, if it just fell into the ashes of the fire and
cooled there. To my untutored eye, at least.

That would be significant in itself. The heat required to melt
such a mass of copper can't be produced in an ordinary open
wood fire. A forced draft fire burning a high carbon fuel such
as charcoal or actual metallurgical grade coal would normally
be required to supply the heat necessary to melt that mass.

Now that's consistent with a smith's forge or a casting furnace.
It isn't consistent with an ordinary wood fire used to anneal
worked native copper. So that lends support to the thesis that
the ancient Native Americans controlled such a high temperature
technology.

OTOH, a forest fire can produce sufficient natural draft to reach
the required temperature. So it is *possible* that R666 was in
such a natural fire. That would explain what we see in the radiograph
without the necessity of claiming high temperature technology for
the ancient Native Americans.

The fact that we have only one artifact showing the characteristic
porosity we'd expect from native copper melted in atmosphere
lends credence to the latter hypothesis. If we saw a *lot* of artifacts
from different locations showing characteristic porosity, that'd be
another story. But no good evidence has been presented to support
that, certainly not the other examples on the web site. The radiographs
of other items on the site are more consistent with wrought items
than cast items.

As I mentioned previously, surface blisters are not what we're
looking for in terms of the porosity characteristic of pure copper
casting. What we need to see is a foam of microscopic bubbles,
and clusters of tiny visible bubbles deep in the metal on the
radiographs. That's absent from the other radiographs on the
site.

Gary

Gary Coffman wrote:

On Sun, 27 Jun 2004 14:59:04 -0500, Tom McDonald wrote:

Gary Coffman wrote:

On Sun, 27 Jun 2004 13:18:58 -0500, Tom McDonald wrote:

Gary Coffman wrote:

The evidence brought out in this thread is that *one* copper artifact
shows radiographic evidence (characteristic porosity) for part of it
being heated above the melting point in atmosphere at some point.
That is in no way conclusive evidence of casting technology. The
piece may have been an attempt at casting, or it may simply have
been overheated while being worked.

Are you referring to the sort of amorphous, three-cornered blob
listed in Conner's web site as 'R666', and in the Milwaukee
Public Museum (where it's curated) as '55786':

http://www.iwaynet.net/~wdc/copper.htm

If so, I have found additional information about that piece.

Yes, that's the one. What have you learned?

I corresponded with Dr. Alex Barker of the Milwaukee Public
Museum about this artifact, since they are curating it there.
His response about the description of the artifact was as follows:

"As to why one might wonder if it had been cast, it's relatively
dense for its size, and one surface is fairly smooth and
rounded--not like the upper surface of cast metal, however, but
one might perhaps imagine it as the bottom of an irregular
puddle of metal."


Interesting that he'd characterize it as "relatively dense for its size".
The density measurement reported on the web site says it is less
dense than ordinary native copper (8.2 vs 8.9). That's consistent
with the porosity shown in the radiograph.

I suspect that Dr Barker has neither metallurgical nor geological
training. So his density report is just that of a layman picking up
a hunk of metal. But if I'm wrong in that supposition, then he is
contradicting the information provided on the web site.

Gary,

He has a background in anthropology, so I wouldn't expect that
he would necessarily have much in the way of metallurgical
training, and his geology might be limited. As you noted, his
observation on the heaviness of the object seemed to belie
amateur status in those fields.

I'm not arguing about the details reported in Conner's web
site. I'm just concerned that his and his sources may have gone
beyond the evidence in certain cases.



The description he gave seems to fit the photo on Connor's
site. It doesn't look like any purpose-made artifact; but it
does look as one might expect a bit of accidentally melted
copper to look, if it just fell into the ashes of the fire and
cooled there. To my untutored eye, at least.


That would be significant in itself. The heat required to melt
such a mass of copper can't be produced in an ordinary open
wood fire. A forced draft fire burning a high carbon fuel such
as charcoal or actual metallurgical grade coal would normally
be required to supply the heat necessary to melt that mass.

Now that's consistent with a smith's forge or a casting furnace.
It isn't consistent with an ordinary wood fire used to anneal
worked native copper. So that lends support to the thesis that
the ancient Native Americans controlled such a high temperature
technology.

OTOH, a forest fire can produce sufficient natural draft to reach
the required temperature. So it is *possible* that R666 was in
such a natural fire. That would explain what we see in the radiograph
without the necessity of claiming high temperature technology for
the ancient Native Americans.

I'm getting around to reading two detailed archaeological
reports on the Riverside site, as well as a short report on
mortuary issues at the site written by Lewis Binford. You have
helped me frame some key questions to keep in mind when reading
them. In addition to the obvious (copper artifacts and
cremation details), you've got me looking for localized,
atypical hearths and discussions about charcoal and/or ash that
might be from forest fires instead of controlled hearth or
cremation fires. Thanks.


The fact that we have only one artifact showing the characteristic
porosity we'd expect from native copper melted in atmosphere
lends credence to the latter hypothesis. If we saw a *lot* of artifacts
from different locations showing characteristic porosity, that'd be
another story. But no good evidence has been presented to support
that, certainly not the other examples on the web site. The radiographs
of other items on the site are more consistent with wrought items
than cast items.

What strikes me about the copper blob we're discussing is that
if it were to have been overpour or other waste from a casting
event, I'd expect it to have been added to a 'try again' pile,
to be melted with other smaller bits for later casting. Of
course, it could have just been forgotten. I'll have to look in
the reports for indications of ceramics, with a specific concern
for what might have been used as crucibles.


As I mentioned previously, surface blisters are not what we're
looking for in terms of the porosity characteristic of pure copper
casting. What we need to see is a foam of microscopic bubbles,
and clusters of tiny visible bubbles deep in the metal on the
radiographs. That's absent from the other radiographs on the
site.

Yes, that's why I was interested in your take on R666/55786.
If there were other good examples of melted copper, I'd have
expected that the web site would have presented them. As it is,
it looks as though I'll have to dig for other examples that
might show casting.

Tom McDonald

On Sun, 27 Jun 2004 19:18:20 -0400, Gary Coffman
wrote:

On Mon, 28 Jun 2004 09:04:48 +1200, Eric Stevens wrote:
On Sun, 27 Jun 2004 03:11:14 -0400, Gary Coffman
wrote:

On Sat, 26 Jun 2004 11:13:49 +1200, Eric Stevens wrote:
On Wed, 23 Jun 2004 23:46:01 -0500, Tom McDonald
wrote:
In the case of the copper artifacts in the upper Great Lakes
area, all of the shapes and structures have been shown to have
been made via cold and hot-working techniques.

This is not my understanding. Metallurgical examination has shown that
some of the artifacts have been cast.

The evidence brought out in this thread is that *one* copper artifact
shows radiographic evidence (characteristic porosity) for part of it
being heated above the melting point in atmosphere at some point.
That is in no way conclusive evidence of casting technology. The
piece may have been an attempt at casting, or it may simply have
been overheated while being worked.

Maybe you missed it but http://www.iwaynet.com/~wdc/copper.htm was
cited a few weeks ago in sci.archaeology and introduces evidence for
the casting of copper. Arlington Mallery's book gives more details
including the results of competent metallurgical examination.

No, I didn't miss it. That's where the reference to artifact R666 was
found. None of the other artifacts shown present convincing evidence
(characteristic porosity) of having been poured in atmosphere.

Did you see my Message-ID:
in which I quote
metallurgical aspects from Mallery?



Eric Stevens

On Sun, 27 Jun 2004 19:00:11 -0400, Gary Coffman
wrote:

On Mon, 28 Jun 2004 09:04:49 +1200, Eric Stevens wrote:
On Sun, 27 Jun 2004 03:03:50 -0400, Gary Coffman
wrote:
On Wed, 23 Jun 2004 23:46:01 -0500, Tom McDonald wrote:
Eric Stevens wrote:
On Fri, 11 Jun 2004 22:57:04 GMT, (Gary Coffman)
wrote:
But that said, casting pure copper is a bitch.


This from the guy who has just written that the task can be undertaken
by low-skilled workers?

Eric, I read that to mean that casting, in general (as with
iron, silver, bronze, gold, etc.) can be done by folks with
fewer skills than smiths. However, copper appears to present
particular problems with casting that are not so pronounced with
other metals, and which require higher skill levels than would
be required by those who cast other metals.

Exactly, and further, skill alone isn't sufficient to make sound
castings of pure copper. The proper equipment is also required.
Specifically, an inert atmosphere furnace. That technology
didn't exist until the late 19th century.

Just as well the ancient egyptians didn't know that they couldn't do
what they were doing. :-)

So, are you claiming to have evidence that the ancient Egyptians
successfully cast pure native copper?

Apart from the fact that it all depends what you mean by 'pure', yes,
I have read to that effect.

The metallurgical references I have say that native copper was
extremely rare in Egypt. Almost all of the copper they had was
refined from ores (smelted), and the results were *not* pure
copper. Rather, they were alloys, whether intentional or not,
of copper, arsenic, zinc, iron, or tin. These alloys behave *very*
differently from pure native copper when casting is attempted.

While not directly addressing the point, you may be interested in
http://www.lehigh.edu/~inarcmet/papers/jfa022002.pdf



Eric Stevens

"Tom McDonald" skrev i meddelandet
...
Gary Coffman wrote:

On Sun, 27 Jun 2004 14:59:04 -0500, Tom McDonald
wrote:

Gary Coffman wrote:

On Sun, 27 Jun 2004 13:18:58 -0500, Tom McDonald
wrote:

Gary Coffman wrote:

The evidence brought out in this thread is that *one* copper artifact
shows radiographic evidence (characteristic porosity) for part of it
being heated above the melting point in atmosphere at some point.
That is in no way conclusive evidence of casting technology. The
piece may have been an attempt at casting, or it may simply have
been overheated while being worked.

Are you referring to the sort of amorphous, three-cornered blob
listed in Conner's web site as 'R666', and in the Milwaukee
Public Museum (where it's curated) as '55786':

http://www.iwaynet.net/~wdc/copper.htm

If so, I have found additional information about that piece.

Yes, that's the one. What have you learned?

I corresponded with Dr. Alex Barker of the Milwaukee Public
Museum about this artifact, since they are curating it there.
His response about the description of the artifact was as follows:

"As to why one might wonder if it had been cast, it's relatively
dense for its size, and one surface is fairly smooth and
rounded--not like the upper surface of cast metal, however, but
one might perhaps imagine it as the bottom of an irregular
puddle of metal."


Interesting that he'd characterize it as "relatively dense for its
size".
The density measurement reported on the web site says it is less
dense than ordinary native copper (8.2 vs 8.9). That's consistent
with the porosity shown in the radiograph.

I suspect that Dr Barker has neither metallurgical nor geological
training. So his density report is just that of a layman picking up
a hunk of metal. But if I'm wrong in that supposition, then he is
contradicting the information provided on the web site.

Gary,

He has a background in anthropology, so I wouldn't expect that
he would necessarily have much in the way of metallurgical
training, and his geology might be limited. As you noted, his
observation on the heaviness of the object seemed to belie
amateur status in those fields.

I'm not arguing about the details reported in Conner's web
site. I'm just concerned that his and his sources may have gone
beyond the evidence in certain cases.



The description he gave seems to fit the photo on Connor's
site. It doesn't look like any purpose-made artifact; but it
does look as one might expect a bit of accidentally melted
copper to look, if it just fell into the ashes of the fire and
cooled there. To my untutored eye, at least.


That would be significant in itself. The heat required to melt
such a mass of copper can't be produced in an ordinary open
wood fire. A forced draft fire burning a high carbon fuel such
as charcoal or actual metallurgical grade coal would normally
be required to supply the heat necessary to melt that mass.

Now that's consistent with a smith's forge or a casting furnace.
It isn't consistent with an ordinary wood fire used to anneal
worked native copper. So that lends support to the thesis that
the ancient Native Americans controlled such a high temperature
technology.

OTOH, a forest fire can produce sufficient natural draft to reach
the required temperature. So it is *possible* that R666 was in
such a natural fire. That would explain what we see in the radiograph
without the necessity of claiming high temperature technology for
the ancient Native Americans.

I'm getting around to reading two detailed archaeological
reports on the Riverside site, as well as a short report on
mortuary issues at the site written by Lewis Binford. You have
helped me frame some key questions to keep in mind when reading
them. In addition to the obvious (copper artifacts and
cremation details), you've got me looking for localized,
atypical hearths and discussions about charcoal and/or ash that
might be from forest fires instead of controlled hearth or
cremation fires. Thanks.


The fact that we have only one artifact showing the characteristic
porosity we'd expect from native copper melted in atmosphere
lends credence to the latter hypothesis. If we saw a *lot* of artifacts
from different locations showing characteristic porosity, that'd be
another story. But no good evidence has been presented to support
that, certainly not the other examples on the web site. The radiographs
of other items on the site are more consistent with wrought items
than cast items.

What strikes me about the copper blob we're discussing is that
if it were to have been overpour or other waste from a casting
event, I'd expect it to have been added to a 'try again' pile,
to be melted with other smaller bits for later casting. Of
course, it could have just been forgotten. I'll have to look in
the reports for indications of ceramics, with a specific concern
for what might have been used as crucibles.

If I remember it correctly, saw a report at my friend's house the other day,
it was in an Ohio site such was found or at least ceramics found was
believed to have been used as crucibles.

Inger E

On Mon, 28 Jun 2004 08:52:10 +1200, Eric Stevens wrote:
On Sun, 27 Jun 2004 02:58:26 -0400, Gary Coffman
wrote:
No trick to melting copper. Doing something intelligent with the molten
metal in an atmospheric environment is a different matter. As I noted
previously, casting pure copper is difficult, even today.

But the question is, how pure was the copper.

The native copper we've been discussing is very high purity.
The halfbreed ore does contain silver, but the silver isn't in
solid solution with the copper (copper-silver alloys are difficult
to produce). Instead it is in the form of distinct crystal inclusions
which would melt out and separate before the copper would melt.

In any case, copper can mostly by prevented from oxidising by melting
it under a layer of crushed coal or charcoal. In fact this method was
used for the production of largely deoxised (tough-pitch) copper in
recent time.

A graphite cover was used to prevent oxidation while melting (coal
won't work because of the large fraction of volatiles, charcoal might
be useable). But you also have to deal with the air entrained when
pouring.

A bottom pour furnace is helpful, but you really need deoxidizers in
the alloy to prevent severe porosity problems. Tin and zinc are the
preferred deoxidizers. Arsenic also works, but the fumes are deadly.
Lead makes the metal more fluid, and assists in filling out the mold.
None of those are naturally present in the native copper we're
discussing.

Also, as a side note, where is the evidence for coal mining or large
scale charcoal production in the area? You don't get to copper
melting temperatures with a simple wood fire. You need a forced
draft fire with a high carbon fuel.

For a people
without inert gas shielded continuous casting furnaces, it would be
nothing but frustration.


Don't under rate the cunning of anceint man.

Don't underestimate the difficulty of getting sound pure copper
castings. Low alloy bronzes and brasses (approx 0.5% to 1% tin
or zinc respectively) aren't too bad to cast, high alloy bronzes
and brasses are easy. But casting pure copper is hard, even
with today's technology.

Again, porosity is the problem, and that should show up on
radiographs, as it does for R666 (which certainly shows evidence
of being melted in atmosphere, though not necessarily evidence
of being cast), but none of the other artifacts presented show
that sort of porosity.

I believe we are agreed that only atmospheric casting was within
reach of the ancient Native Americans (or ancient Old World
founders for that matter), so we *should* see characteristic
porosity in any pure copper items they attempted to cast. Now
of course the Old Worlders had the advantage of ores which
did contain suitable deoxidizers. They weren't actually casting
pure copper. But the Michigan copper was essentially pure
native copper.

Gary

On Mon, 28 Jun 2004 06:46:49 GMT, "Inger E Johansson" wrote:
If I remember it correctly, saw a report at my friend's house the other day,
it was in an Ohio site such was found or at least ceramics found was
believed to have been used as crucibles.

What I've seen since I started looking into this is a report of a purported
ceramic mold fragment discovered in Ohio. However, there is considerable
disagreement as to whether that actually is a mold fragment or not. It is
also far from the native copper sites being discussed, and hasn't been
dated to the time frame under discussion. So it sheds very little light on
the subject of pure copper casting.

Gary

On Mon, 28 Jun 2004 17:38:04 +1200, Eric Stevens wrote:
On Sun, 27 Jun 2004 19:00:11 -0400, Gary Coffman
wrote:
On Mon, 28 Jun 2004 09:04:49 +1200, Eric Stevens wrote:
On Sun, 27 Jun 2004 03:03:50 -0400, Gary Coffman
wrote:
On Wed, 23 Jun 2004 23:46:01 -0500, Tom McDonald wrote:
Eric Stevens wrote:
On Fri, 11 Jun 2004 22:57:04 GMT, (Gary Coffman)
wrote:
But that said, casting pure copper is a bitch.


This from the guy who has just written that the task can be undertaken
by low-skilled workers?

Eric, I read that to mean that casting, in general (as with
iron, silver, bronze, gold, etc.) can be done by folks with
fewer skills than smiths. However, copper appears to present
particular problems with casting that are not so pronounced with
other metals, and which require higher skill levels than would
be required by those who cast other metals.

Exactly, and further, skill alone isn't sufficient to make sound
castings of pure copper. The proper equipment is also required.
Specifically, an inert atmosphere furnace. That technology
didn't exist until the late 19th century.

Just as well the ancient egyptians didn't know that they couldn't do
what they were doing. :-)

So, are you claiming to have evidence that the ancient Egyptians
successfully cast pure native copper?

Apart from the fact that it all depends what you mean by 'pure', yes,
I have read to that effect.

The metallurgical references I have say that native copper was
extremely rare in Egypt. Almost all of the copper they had was
refined from ores (smelted), and the results were *not* pure
copper. Rather, they were alloys, whether intentional or not,
of copper, arsenic, zinc, iron, or tin. These alloys behave *very*
differently from pure native copper when casting is attempted.

While not directly addressing the point, you may be interested in
http://www.lehigh.edu/~inarcmet/papers/jfa022002.pdf

While not Egyptian, and the artifacts analyzed show evidence of
being wrought rather than cast, the chemical analysis does back
my position. The metals being worked were alloys, not pure native
copper.

Gary

Inger E Johansson wrote:
"Tom McDonald" skrev i meddelandet
...

snip

What strikes me about the copper blob we're discussing is that
if it were to have been overpour or other waste from a casting
event, I'd expect it to have been added to a 'try again' pile,
to be melted with other smaller bits for later casting. Of
course, it could have just been forgotten. I'll have to look in
the reports for indications of ceramics, with a specific concern
for what might have been used as crucibles.


If I remember it correctly, saw a report at my friend's house the other day,
it was in an Ohio site such was found or at least ceramics found was
believed to have been used as crucibles.

Inger E

Inger,

I'd like to have information about that site in Ohio. I'm
especially interested in:

Date(s) and culture(s) of the ceramics;

Reports and photos about the potential crucibles;

Location(s) of the find(s);

References to work on the artifacts, and/or primary
investigator(s) on the studies.

Thanks.

Tom McDonald

Gary Coffman wrote:

On Mon, 28 Jun 2004 09:04:49 +1200, Eric Stevens wrote:
On Sun, 27 Jun 2004 03:03:50 -0400, Gary Coffman
wrote:
On Wed, 23 Jun 2004 23:46:01 -0500, Tom McDonald wrote:
Eric Stevens wrote:
On Fri, 11 Jun 2004 22:57:04 GMT, (Gary Coffman)
wrote:
But that said, casting pure copper is a bitch.


This from the guy who has just written that the task can be undertaken
by low-skilled workers?

Eric, I read that to mean that casting, in general (as with
iron, silver, bronze, gold, etc.) can be done by folks with
fewer skills than smiths. However, copper appears to present
particular problems with casting that are not so pronounced with
other metals, and which require higher skill levels than would
be required by those who cast other metals.

Exactly, and further, skill alone isn't sufficient to make sound
castings of pure copper. The proper equipment is also required.
Specifically, an inert atmosphere furnace. That technology
didn't exist until the late 19th century.

Just as well the ancient egyptians didn't know that they couldn't do
what they were doing. :-)

So, are you claiming to have evidence that the ancient Egyptians
successfully cast pure native copper?

The metallurgical references I have say that native copper was
extremely rare in Egypt. Almost all of the copper they had was
refined from ores (smelted), and the results were *not* pure
copper. Rather, they were alloys, whether intentional or not,
of copper, arsenic, zinc, iron, or tin. These alloys behave *very*
differently from pure native copper when casting is attempted.

Gary

Well, Gary, the folowing sure seems to imply that the
ancient Egyptian did some copper casting.

[quote]

Ancient Egyptian raw materials: metals - copper, bronze,
iron, gold, silver, lead
http://nefertiti.iwebland.com/trades/metals.htm


copper objects [rather than bronze]:

The objects were generally cast, which is quite difficult to
do with copper because of the formation of gas bubbles
during the pouring of the metal and its shrinking when it
cooled down. Then they were hammered cold to give them their
final form.

[unquote]

Yuri.

Yuri Kuchinsky -=O=- http://www.trends.ca/~yuku

Reality is that which, when you stop believing
in it, doesn't go away -=O=- Philip K. Dick

Gary Coffman wrote:

On Wed, 23 Jun 2004 23:46:01 -0500, Tom McDonald wrote:
Eric Stevens wrote:
On Fri, 11 Jun 2004 22:57:04 GMT, (Gary Coffman)
wrote:
But that said, casting pure copper is a bitch.


This from the guy who has just written that the task can be undertaken
by low-skilled workers?

Eric, I read that to mean that casting, in general (as with
iron, silver, bronze, gold, etc.) can be done by folks with
fewer skills than smiths. However, copper appears to present
particular problems with casting that are not so pronounced with
other metals, and which require higher skill levels than would
be required by those who cast other metals.

Exactly, and further, skill alone isn't sufficient to make sound
castings of pure copper. The proper equipment is also required.
Specifically, an inert atmosphere furnace. That technology
didn't exist until the late 19th century.

Gary

Hi, Gary,

Here you seem to be implying that copper casting wasn't done
in the ancient world at all.

You couldn't be more wrong, my friend... Sure seems to me
like you're not very knowledgeable about the ways that the
ancient peoples worked with metals.

And this implies that your general knowledge about
metalworking is rather deficient, since you've reached the
above conclusion based on it, rather than on your
familiarity with archaeological evidence.

So here's some archaeological evidence for a change, that
refutes your speculations about the ancient peoples not
casting pure copper.

[quotes]

INDIA

http://www.hindunet.org/hindu_histor.../artefacts.htm

Melting of native copper was done by putting the regulus
[lump of copper] over furnace or fire in a crucible and then
casting it.


IRELAND

Copper and Tin Mining in Ireland in the Bronze Age
http://www.thecelticplanet.com/mining.htm

It is estimated that in the early Bronze Age in Ireland, not
more than 14% of artifacts were of bronze. The remainder
were made from copper only


SOUTHERN SIBERIA

http://faculty.web.waseda.ac.jp/yukis/sougen13.mei.html

Intriguingly, the majority of cauldrons recovered in
southern Siberia were also made of pure copper instead of
tin bronze. According to Bogdanova-Berezobskaya (1963: 136,
153), among the twenty cauldrons analyzed, thirteen are pure
copper, five arsenical copper (As 1-1.5%), one tin bronze,
and one Cu-Sn-Pb alloy.

[the date range above seems to be 7th-8th centuries BC]


http://www.thecopperlink.com/product...i-of_index.php

the oldest artefacts are not made of copper tin alloys, they
are made of pure copper.

Some examples of early smelted copper artefacts:

-- 3800 BC Spatula, Chisel, Awl - Iran (Yahya)
-- 3500 BC Flat axe - Egypt

[end quotes]

So it's never too late to educate yourself about such
things, Gary.

Best regards,

Yuri.

Yuri Kuchinsky -=O=- http://www.trends.ca/~yuku

Reality is that which, when you stop believing
in it, doesn't go away -=O=- Philip K. Dick

Yuri Kuchinsky wrote:

Gary Coffman wrote:

On Mon, 28 Jun 2004 09:04:49 +1200, Eric Stevens wrote:

On Sun, 27 Jun 2004 03:03:50 -0400, Gary Coffman
wrote:

On Wed, 23 Jun 2004 23:46:01 -0500, Tom McDonald wrote:

Eric Stevens wrote:

On Fri, 11 Jun 2004 22:57:04 GMT, (Gary Coffman)
wrote:

But that said, casting pure copper is a bitch.


This from the guy who has just written that the task can be undertaken
by low-skilled workers?

Eric, I read that to mean that casting, in general (as with
iron, silver, bronze, gold, etc.) can be done by folks with
fewer skills than smiths. However, copper appears to present
particular problems with casting that are not so pronounced with
other metals, and which require higher skill levels than would
be required by those who cast other metals.

Exactly, and further, skill alone isn't sufficient to make sound
castings of pure copper. The proper equipment is also required.
Specifically, an inert atmosphere furnace. That technology
didn't exist until the late 19th century.

Just as well the ancient egyptians didn't know that they couldn't do
what they were doing. :-)

So, are you claiming to have evidence that the ancient Egyptians
successfully cast pure native copper?

The metallurgical references I have say that native copper was
extremely rare in Egypt. Almost all of the copper they had was
refined from ores (smelted), and the results were *not* pure
copper. Rather, they were alloys, whether intentional or not,
of copper, arsenic, zinc, iron, or tin. These alloys behave *very*
differently from pure native copper when casting is attempted.

Gary


Well, Gary, the folowing sure seems to imply that the
ancient Egyptian did some copper casting.

[quote]

Ancient Egyptian raw materials: metals - copper, bronze,
iron, gold, silver, lead
http://nefertiti.iwebland.com/trades/metals.htm


copper objects [rather than bronze]:

The objects were generally cast, which is quite difficult to
do with copper because of the formation of gas bubbles
during the pouring of the metal and its shrinking when it
cooled down. Then they were hammered cold to give them their
final form.

[unquote]

Yuri,

Your site tells us that copper ore was what was available, not
native copper; and that it had to be smelted before use. IOW,
it's not clear whether the Egyptians ever had copper of the
purity of the native copper in the upper Great Lakes area. In
addition, the smelting and melting of that copper would more
than likely have resulted in a copper alloy, not pure copper.

Of course, if you have better evidence that shows Egyptians
cast 99+% pure copper, you are welcome to present it here. I
for one would be very interested in that evidence.

Tom McDonald

On Mon, 28 Jun 2004 13:22:35 -0400, Gary Coffman
wrote:

On Mon, 28 Jun 2004 17:38:04 +1200, Eric Stevens wrote:
On Sun, 27 Jun 2004 19:00:11 -0400, Gary Coffman
wrote:
On Mon, 28 Jun 2004 09:04:49 +1200, Eric Stevens wrote:
On Sun, 27 Jun 2004 03:03:50 -0400, Gary Coffman
wrote:
On Wed, 23 Jun 2004 23:46:01 -0500, Tom McDonald wrote:
Eric Stevens wrote:
On Fri, 11 Jun 2004 22:57:04 GMT, (Gary Coffman)
wrote:
But that said, casting pure copper is a bitch.


This from the guy who has just written that the task can be undertaken
by low-skilled workers?

Eric, I read that to mean that casting, in general (as with
iron, silver, bronze, gold, etc.) can be done by folks with
fewer skills than smiths. However, copper appears to present
particular problems with casting that are not so pronounced with
other metals, and which require higher skill levels than would
be required by those who cast other metals.

Exactly, and further, skill alone isn't sufficient to make sound
castings of pure copper. The proper equipment is also required.
Specifically, an inert atmosphere furnace. That technology
didn't exist until the late 19th century.

Just as well the ancient egyptians didn't know that they couldn't do
what they were doing. :-)

So, are you claiming to have evidence that the ancient Egyptians
successfully cast pure native copper?

Apart from the fact that it all depends what you mean by 'pure', yes,
I have read to that effect.

The metallurgical references I have say that native copper was
extremely rare in Egypt. Almost all of the copper they had was
refined from ores (smelted), and the results were *not* pure
copper. Rather, they were alloys, whether intentional or not,
of copper, arsenic, zinc, iron, or tin. These alloys behave *very*
differently from pure native copper when casting is attempted.

While not directly addressing the point, you may be interested in
http://www.lehigh.edu/~inarcmet/papers/jfa022002.pdf

While not Egyptian, and the artifacts analyzed show evidence of
being wrought rather than cast, the chemical analysis does back
my position. The metals being worked were alloys, not pure native
copper.

As I said, it all depends upon what you mean by 'pure'.



Eric Stevens

On Mon, 28 Jun 2004 13:07:35 -0400, Gary Coffman
wrote:

On Mon, 28 Jun 2004 08:52:10 +1200, Eric Stevens wrote:
On Sun, 27 Jun 2004 02:58:26 -0400, Gary Coffman
wrote:
No trick to melting copper. Doing something intelligent with the molten
metal in an atmospheric environment is a different matter. As I noted
previously, casting pure copper is difficult, even today.

But the question is, how pure was the copper.

The native copper we've been discussing is very high purity.
The halfbreed ore does contain silver, but the silver isn't in
solid solution with the copper (copper-silver alloys are difficult
to produce). Instead it is in the form of distinct crystal inclusions
which would melt out and separate before the copper would melt.

In any case, copper can mostly by prevented from oxidising by melting
it under a layer of crushed coal or charcoal. In fact this method was
used for the production of largely deoxised (tough-pitch) copper in
recent time.

A graphite cover was used to prevent oxidation while melting (coal
won't work because of the large fraction of volatiles, charcoal might
be useable). But you also have to deal with the air entrained when
pouring.

Here is a quote from 'Metallurgy for Engineers' Rollason, 2nd Edition,
first published 1939:

Begin quote:
---------------------------------
Production of Tough Pitch Copper. In fire-refining copper the
impurities are removed by oxidising the metal until about 4 per cent
copper oxide (Cu20) is absorbed. During this stage the impurities form
oxides more readily than the copper and are removed as a slag or
evolved as gas. The last impurity so removed is sulphur which is not
completely driven off as sulphur dioxide by mere oxidation, but to
remove the last traces the metal has to be violently agitated by
poling, i.e. introducing an unseasoned piece of wood under the
surface. This causes a miniature fountain of molten copper, and allows
the air to come into contact with the spraying metal. Small test
castings or button castings are taken to indicate the state of the
metal. With sulphur present the ingot spurts just as it goes solid due
to the evolution of gas (SO2), but as the sulphur is reduced in amount
the surface of the ingot sinks in the manner normal to most metals. If
a micro-examination is made of this metal it will be found to contain
globules of copper oxide in the form of a eutectic (Cu-Cu2O). A layer
of crushed coal is then placed on the molten copper, and as poling
continues the copper oxide is reduced and when a content of about 0.04
to 0.08 per cent oxygen is reached the surface of the button remains
level and the properties of the metal are good, in other words
"tough." The lower the oxygen, the higher the so-called "pitch" and
vice versa, hence the name "Tough Pitch." As poling continues past
this point the copper absorbs hydrogen from the furnace gases and when
cast the metal rises on solidification.
These changes in behaviour, micro-structure and mechanical properties
are due to the influence of hydrogen and oxygen on the copper.
----------------------------------------
End quote

The above confirms not only the use of crushed coal but also the
primitive nature of the processes by means of which relatively pure
copper was produced even in the 20th century. Stirring with a piece of
unseasoned wood is a practice which may have roots going back for
millenia.

My point is that our ancestors have had a habit of producing materials
with primitive techniques which we have now largely forgotten about.
The fact the we now do things only with modern gizmos doen't mean that
our ancestors couldn't do much the same thing some other way.


A bottom pour furnace is helpful, but you really need deoxidizers in
the alloy to prevent severe porosity problems. Tin and zinc are the
preferred deoxidizers. Arsenic also works, but the fumes are deadly.
Lead makes the metal more fluid, and assists in filling out the mold.
None of those are naturally present in the native copper we're
discussing.

Also, as a side note, where is the evidence for coal mining or large
scale charcoal production in the area? You don't get to copper
melting temperatures with a simple wood fire. You need a forced
draft fire with a high carbon fuel.

A good bed of well ventilated charcoal will suffice. One often finds
melted copper in the remains of burned out buildings.

For a people
without inert gas shielded continuous casting furnaces, it would be
nothing but frustration.


Don't under rate the cunning of anceint man.

Don't underestimate the difficulty of getting sound pure copper
castings. Low alloy bronzes and brasses (approx 0.5% to 1% tin
or zinc respectively) aren't too bad to cast, high alloy bronzes
and brasses are easy. But casting pure copper is hard, even
with today's technology.

Once again, it depends what you mean by pure. Somewhere I have seen
reference to a recognised ancient copper alloy containing 0.5% As
which was produced by addition of the As. Clearly they were able to
produce copper with less than that level of As.

Again, porosity is the problem, and that should show up on
radiographs, as it does for R666 (which certainly shows evidence
of being melted in atmosphere, though not necessarily evidence
of being cast), but none of the other artifacts presented show
that sort of porosity.

I believe we are agreed that only atmospheric casting was within
reach of the ancient Native Americans (or ancient Old World
founders for that matter), so we *should* see characteristic
porosity in any pure copper items they attempted to cast.

Only if they used the relatively pure meteoric copper of Michigan. It
was laikely to be naturally alloyed if it was smelted.

Now
of course the Old Worlders had the advantage of ores which
did contain suitable deoxidizers. They weren't actually casting
pure copper. But the Michigan copper was essentially pure
native copper.

But it wasn't the only source of copper.




Eric Stevens

Eric Stevens wrote:

On Mon, 28 Jun 2004 13:22:35 -0400, Gary Coffman
wrote:


On Mon, 28 Jun 2004 17:38:04 +1200, Eric Stevens wrote:

On Sun, 27 Jun 2004 19:00:11 -0400, Gary Coffman
wrote:

On Mon, 28 Jun 2004 09:04:49 +1200, Eric Stevens wrote:

On Sun, 27 Jun 2004 03:03:50 -0400, Gary Coffman
wrote:

On Wed, 23 Jun 2004 23:46:01 -0500, Tom McDonald wrote:

Eric Stevens wrote:

On Fri, 11 Jun 2004 22:57:04 GMT, (Gary Coffman)
wrote:

But that said, casting pure copper is a bitch.


This from the guy who has just written that the task can be undertaken
by low-skilled workers?

Eric, I read that to mean that casting, in general (as with
iron, silver, bronze, gold, etc.) can be done by folks with
fewer skills than smiths. However, copper appears to present
particular problems with casting that are not so pronounced with
other metals, and which require higher skill levels than would
be required by those who cast other metals.

Exactly, and further, skill alone isn't sufficient to make sound
castings of pure copper. The proper equipment is also required.
Specifically, an inert atmosphere furnace. That technology
didn't exist until the late 19th century.

Just as well the ancient egyptians didn't know that they couldn't do
what they were doing. :-)

So, are you claiming to have evidence that the ancient Egyptians
successfully cast pure native copper?

Apart from the fact that it all depends what you mean by 'pure', yes,
I have read to that effect.

The metallurgical references I have say that native copper was
extremely rare in Egypt. Almost all of the copper they had was
refined from ores (smelted), and the results were *not* pure
copper. Rather, they were alloys, whether intentional or not,
of copper, arsenic, zinc, iron, or tin. These alloys behave *very*
differently from pure native copper when casting is attempted.

While not directly addressing the point, you may be interested in
http://www.lehigh.edu/~inarcmet/papers/jfa022002.pdf

While not Egyptian, and the artifacts analyzed show evidence of
being wrought rather than cast, the chemical analysis does back
my position. The metals being worked were alloys, not pure native
copper.


As I said, it all depends upon what you mean by 'pure'.

Eric,

In the context of this thread, at least its original context,
the copper was native copper in the upper Great Lakes area of
the US and Canada. That copper is typically well over 99% pure
out of the ground, and does not have to be smelted to remove
impurities. If another context is in evidence, then a
definition of the term 'pure' is needed.

In the cases Yuri noted (e.g.: Egypt, Harrapa, China), that
copper was apparently smelted from ore, and analysis of
individual artifacts would be necessary to describe the ratio of
copper to alloy materials. In one of Yuri's examples, 'pure'
copper artifacts were all below 98.8% copper.

I agree, therefore, that one cannot take a statement that some
artifact or artifact type was 'pure copper' at face value. It
needs to be quantified.

Tom McDonald

Eric Stevens wrote:

On Mon, 28 Jun 2004 13:07:35 -0400, Gary Coffman
wrote:

snip

Now
of course the Old Worlders had the advantage of ores which
did contain suitable deoxidizers. They weren't actually casting
pure copper. But the Michigan copper was essentially pure
native copper.


But it wasn't the only source of copper.

Eric,

This thread began, and has mostly developed, around that
Michigan (with some from Wisconsin and Minnesota) native copper,
more specifically its use in the upper Great Lakes area.

Yuri has begun a thread about copper casting outside of this
area. Perhaps that would be a better venue for this more
general discussion of ancient copper.

Tom McDonald

Tom McDonald wrote in message ...
Eric,

In the context of this thread, at least its original context,
the copper was native copper in the upper Great Lakes area of
the US and Canada. That copper is typically well over 99% pure
out of the ground, and does not have to be smelted to remove
impurities. If another context is in evidence, then a
definition of the term 'pure' is needed.

In the cases Yuri noted (e.g.: Egypt, Harrapa, China), that
copper was apparently smelted from ore, and analysis of
individual artifacts would be necessary to describe the ratio of
copper to alloy materials. In one of Yuri's examples, 'pure'
copper artifacts were all below 98.8% copper.

I agree, therefore, that one cannot take a statement that some
artifact or artifact type was 'pure copper' at face value. It
needs to be quantified.

Tom McDonald



Much has been bandied about concerning the purity of the copper from the UP,
but you must realize that the same geological process that separates the
copper also separates several other metals at the same time. It does not
place them miles apart but leaves the next to each other, fractions of a
millimeter apart.
for some clarification we will define some vocabulary.

Native copper
This is copper that was left in it's metallic state by the process that
concentrated it. It can be loose, or they can be stuck in a hunk of matrix
exactly as they came out of the ground with other native metals in close
proximity.
Drift copper
This is native copper that has been pounded from its matrix by glacial
action.
Placer deposit
This is a deposit of native metal that has been removed from it's matrix
by erosion (glacial or otherwise) moved from it's original location (usually
by wind or water) and, by nature of its specific gravity and it's resistance
to the motive force has been concentrate with other bits of metal with like
characteristics.

The native copper of the UP is unusually pure. This does not, however, mean
that every piece of rock with copper in it contains only copper.

Below is snip from a site about gold mining in the UP.

..http://www.geo.msu.edu/geo333/gold.html


In June the following year(1846), Houghton’s younger brother Jacob, found a
vein of native copper on the Keweenaw Peninsula which held a small amount of
gold. An assay yielded 10.25 ounces of copper, 1.75 ounces of silver and 12
grains of gold from the 28-ounce specimen



You can see that this particular sample was nearly 15% silver!

Drift copper has had most of the other materials removed by mechanical
action and is usually very pure.

The specific gravities of silver, copper etc. are actually quite close when
compared to sand and placer deposits may contain these in any mix.

Now as to melting.

These native metals are melted for one of three basic reasons.

One, to change it's shape to a finished product
Even today, casting generally produces products that are inferior to
wrought. It is only used when the form cannot economically be produced any
other way,
It is fairly difficult with pure copper, and frankly, if you found a 3
lb hunk of drift copper you would be better off pounding it to shape.

Two, to amalgamate several smaller pieces into one or more larger ones.
The purpose of this is not ,necessarily, to produce a finished product,
but to produce an ingot . Despite copper's casting difficulties, we have
managed to pour ingots of it for almost as long as we have worked metals.
The beauty of the ingot is that if you make it big enough, you can cut
off the bad parts, melt them into the next ingot and pound the rest into
whatever you want.
However, since parent metal is no longer a single nugget of pure copper,
the purity of the casting can be anything.

Three, to separate the metals from the matrix.
This too produces a fine ingot and in the case of Mr. Houghton's sample,
one with 15% silver .


Paul K. DIckman

On Tue, 29 Jun 2004 09:49:39 +1200, Eric Stevens wrote:
On Mon, 28 Jun 2004 13:07:35 -0400, Gary Coffman
wrote:
On Mon, 28 Jun 2004 08:52:10 +1200, Eric Stevens wrote:
On Sun, 27 Jun 2004 02:58:26 -0400, Gary Coffman
wrote:
No trick to melting copper. Doing something intelligent with the molten
metal in an atmospheric environment is a different matter. As I noted
previously, casting pure copper is difficult, even today.

But the question is, how pure was the copper.

The native copper we've been discussing is very high purity.
The halfbreed ore does contain silver, but the silver isn't in
solid solution with the copper (copper-silver alloys are difficult
to produce). Instead it is in the form of distinct crystal inclusions
which would melt out and separate before the copper would melt.

In any case, copper can mostly by prevented from oxidising by melting
it under a layer of crushed coal or charcoal. In fact this method was
used for the production of largely deoxised (tough-pitch) copper in
recent time.

A graphite cover was used to prevent oxidation while melting (coal
won't work because of the large fraction of volatiles, charcoal might
be useable). But you also have to deal with the air entrained when
pouring.

Here is a quote from 'Metallurgy for Engineers' Rollason, 2nd Edition,
first published 1939:

Begin quote:
---------------------------------
Production of Tough Pitch Copper. In fire-refining copper the
impurities are removed by oxidising the metal until about 4 per cent
copper oxide (Cu20) is absorbed. During this stage the impurities form
oxides more readily than the copper and are removed as a slag or
evolved as gas. The last impurity so removed is sulphur which is not
completely driven off as sulphur dioxide by mere oxidation, but to
remove the last traces the metal has to be violently agitated by
poling, i.e. introducing an unseasoned piece of wood under the
surface. This causes a miniature fountain of molten copper, and allows
the air to come into contact with the spraying metal. Small test
castings or button castings are taken to indicate the state of the
metal. With sulphur present the ingot spurts just as it goes solid due
to the evolution of gas (SO2), but as the sulphur is reduced in amount
the surface of the ingot sinks in the manner normal to most metals. If
a micro-examination is made of this metal it will be found to contain
globules of copper oxide in the form of a eutectic (Cu-Cu2O). A layer
of crushed coal is then placed on the molten copper, and as poling
continues the copper oxide is reduced and when a content of about 0.04
to 0.08 per cent oxygen is reached the surface of the button remains
level and the properties of the metal are good, in other words
"tough." The lower the oxygen, the higher the so-called "pitch" and
vice versa, hence the name "Tough Pitch." As poling continues past
this point the copper absorbs hydrogen from the furnace gases and when
cast the metal rises on solidification.
These changes in behaviour, micro-structure and mechanical properties
are due to the influence of hydrogen and oxygen on the copper.
----------------------------------------
End quote

The above confirms not only the use of crushed coal but also the
primitive nature of the processes by means of which relatively pure
copper was produced even in the 20th century. Stirring with a piece of
unseasoned wood is a practice which may have roots going back for
millenia.

The quote is a procedure for smelting chalcopyrite ore. That's a very
different procedure from what is required to process pure native copper.
Apples and oranges.

A bottom pour furnace is helpful, but you really need deoxidizers in
the alloy to prevent severe porosity problems. Tin and zinc are the
preferred deoxidizers. Arsenic also works, but the fumes are deadly.
Lead makes the metal more fluid, and assists in filling out the mold.
None of those are naturally present in the native copper we're
discussing.

Also, as a side note, where is the evidence for coal mining or large
scale charcoal production in the area? You don't get to copper
melting temperatures with a simple wood fire. You need a forced
draft fire with a high carbon fuel.

A good bed of well ventilated charcoal will suffice. One often finds
melted copper in the remains of burned out buildings.

A fully engulfed large building, or a forest fire, can produce sufficient
natural draft to reach copper melting temperature, but you'd need a
forced draft for a simple bed of charcoal. For doing very small amounts
of metal, such as small silver jewelry items, blowpipes would suffice, but
for doing anything on the order of the size of the artifacts we've been
examining, a bellows or blower would be required, and a *lot* of charcoal.

Let me propose that you conduct an experiment. Go to your local "high
end" audio shop and purchase some oxygen free copper "monster" wire
(similar properties to native copper). Now try to melt it in your backyard
barbeque. The insulation will burn off, but I'll be very surprised if you can
get the wire to melt without a forced air draft and *several* loads of
charcoal.

Making charcoal is an industrial enterprise in itself. I'm asking is there
any evidence of such activity in the area under discussion? So far I
have seen no reference to such activities. Nor have I seen any reference
to coal mining activity in the area. All that has been reported is mining
of native copper deposits.

I believe we are agreed that only atmospheric casting was within
reach of the ancient Native Americans (or ancient Old World
founders for that matter), so we *should* see characteristic
porosity in any pure copper items they attempted to cast.

Only if they used the relatively pure meteoric copper of Michigan. It
was laikely to be naturally alloyed if it was smelted.

Meteoric copper? Perhaps you're thinking of iron. The copper we're
discussing is native copper. Native copper is the result of a natural
geochemical leaching process in certain types of rock formations.
It results in extremely high purity copper.

Now
of course the Old Worlders had the advantage of ores which
did contain suitable deoxidizers. They weren't actually casting
pure copper. But the Michigan copper was essentially pure
native copper.

But it wasn't the only source of copper.

True, there are impure ores present in the region as well. But
there is absolutely no evidence that any of it was mined or
processed prior to the latter part of the 19th century. Further,
the impure ores which are present contain iron and sulphur
as their major contaminants. Those impurities are extremely
undesireable in copper that is to be cast. The ore has to be
smelted to remove those impurities.

No significant amounts of tin, zinc, arsenic, or lead, which
would improve casting qualities, are present in the ores of
the region. So even if the ancients had adulterated their
native copper with these ores, the result would not be an
improvement in the ability to cast objects from the resultant
mixture.

The ancients lacked a scientific understanding of metallurgy,
but they weren't stupid. They proceded by a sequence of trial
and error steps. If they added something, and the result was
worse, they'd quickly understand not to do that again. Since
the Native Americans in Michigan already had access to very
high purity native copper, and any local adulterant they added
would only make its properties worse, I'd suggest that they
quickly learned not to add any adulterants.

Now the situation was different in the Old World. The metalworkers
there had access to adulterants which *would* improve the casting
properties of copper, and they fairly quickly learned to add such
materials to their copper. That's not because they were brighter,
it is simply because they had materials at hand which weren't
available to the ancients of Michigan.

Gary

Paul K. Dickman wrote:

Tom McDonald wrote in message ...

Eric,

In the context of this thread, at least its original context,
the copper was native copper in the upper Great Lakes area of
the US and Canada. That copper is typically well over 99% pure
out of the ground, and does not have to be smelted to remove
impurities. If another context is in evidence, then a
definition of the term 'pure' is needed.

In the cases Yuri noted (e.g.: Egypt, Harrapa, China), that
copper was apparently smelted from ore, and analysis of
individual artifacts would be necessary to describe the ratio of
copper to alloy materials. In one of Yuri's examples, 'pure'
copper artifacts were all below 98.8% copper.

I agree, therefore, that one cannot take a statement that some
artifact or artifact type was 'pure copper' at face value. It
needs to be quantified.

Tom McDonald




Much has been bandied about concerning the purity of the copper from the UP,
but you must realize that the same geological process that separates the
copper also separates several other metals at the same time. It does not
place them miles apart but leaves the next to each other, fractions of a
millimeter apart.
for some clarification we will define some vocabulary.

Native copper
This is copper that was left in it's metallic state by the process that
concentrated it. It can be loose, or they can be stuck in a hunk of matrix
exactly as they came out of the ground with other native metals in close
proximity.
Drift copper
This is native copper that has been pounded from its matrix by glacial
action.
Placer deposit
This is a deposit of native metal that has been removed from it's matrix
by erosion (glacial or otherwise) moved from it's original location (usually
by wind or water) and, by nature of its specific gravity and it's resistance
to the motive force has been concentrate with other bits of metal with like
characteristics.

The native copper of the UP is unusually pure. This does not, however, mean
that every piece of rock with copper in it contains only copper.

Below is snip from a site about gold mining in the UP.

.http://www.geo.msu.edu/geo333/gold.html


In June the following year(1846), Houghton’s younger brother Jacob, found a
vein of native copper on the Keweenaw Peninsula which held a small amount of
gold. An assay yielded 10.25 ounces of copper, 1.75 ounces of silver and 12
grains of gold from the 28-ounce specimen



You can see that this particular sample was nearly 15% silver!

Drift copper has had most of the other materials removed by mechanical
action and is usually very pure.

The specific gravities of silver, copper etc. are actually quite close when
compared to sand and placer deposits may contain these in any mix.

Now as to melting.

These native metals are melted for one of three basic reasons.

One, to change it's shape to a finished product
Even today, casting generally produces products that are inferior to
wrought. It is only used when the form cannot economically be produced any
other way,
It is fairly difficult with pure copper, and frankly, if you found a 3
lb hunk of drift copper you would be better off pounding it to shape.

Two, to amalgamate several smaller pieces into one or more larger ones.
The purpose of this is not ,necessarily, to produce a finished product,
but to produce an ingot . Despite copper's casting difficulties, we have
managed to pour ingots of it for almost as long as we have worked metals.
The beauty of the ingot is that if you make it big enough, you can cut
off the bad parts, melt them into the next ingot and pound the rest into
whatever you want.
However, since parent metal is no longer a single nugget of pure copper,
the purity of the casting can be anything.

Three, to separate the metals from the matrix.
This too produces a fine ingot and in the case of Mr. Houghton's sample,
one with 15% silver .


Paul K. DIckman

Paul,

I'm getting a good free education in this copper business. I
thank you and Gary for your tutelage.

I don't recall reading anything about, for instance, silver
artifacts in the upper Great Lakes area; but this doesn't mean
it wasn't used. I rather suspect that folks were breaking rocks
to extract copper, and may have discarded as debitage the
non-copper bits.

I'll have to look into this, as it would seem that silver might
have been present in large enough amounts that it might have
wound up in archaeological contexts. And, of course, when white
folks came later to investigate and further exploit some of the
copper deposits, I'd be surprised if any silver were to have
been ignored by them.

Tom McDonald

On Mon, 28 Jun 2004 21:45:11 -0400, Gary Coffman
wrote:

On Tue, 29 Jun 2004 09:49:39 +1200, Eric Stevens wrote:
On Mon, 28 Jun 2004 13:07:35 -0400, Gary Coffman
wrote:
On Mon, 28 Jun 2004 08:52:10 +1200, Eric Stevens wrote:
On Sun, 27 Jun 2004 02:58:26 -0400, Gary Coffman
wrote:
No trick to melting copper. Doing something intelligent with the molten
metal in an atmospheric environment is a different matter. As I noted
previously, casting pure copper is difficult, even today.

But the question is, how pure was the copper.

The native copper we've been discussing is very high purity.
The halfbreed ore does contain silver, but the silver isn't in
solid solution with the copper (copper-silver alloys are difficult
to produce). Instead it is in the form of distinct crystal inclusions
which would melt out and separate before the copper would melt.

In any case, copper can mostly by prevented from oxidising by melting
it under a layer of crushed coal or charcoal. In fact this method was
used for the production of largely deoxised (tough-pitch) copper in
recent time.

A graphite cover was used to prevent oxidation while melting (coal
won't work because of the large fraction of volatiles, charcoal might
be useable). But you also have to deal with the air entrained when
pouring.

Here is a quote from 'Metallurgy for Engineers' Rollason, 2nd Edition,
first published 1939:

Begin quote:
---------------------------------
Production of Tough Pitch Copper. In fire-refining copper the
impurities are removed by oxidising the metal until about 4 per cent
copper oxide (Cu20) is absorbed. During this stage the impurities form
oxides more readily than the copper and are removed as a slag or
evolved as gas. The last impurity so removed is sulphur which is not
completely driven off as sulphur dioxide by mere oxidation, but to
remove the last traces the metal has to be violently agitated by
poling, i.e. introducing an unseasoned piece of wood under the
surface. This causes a miniature fountain of molten copper, and allows
the air to come into contact with the spraying metal. Small test
castings or button castings are taken to indicate the state of the
metal. With sulphur present the ingot spurts just as it goes solid due
to the evolution of gas (SO2), but as the sulphur is reduced in amount
the surface of the ingot sinks in the manner normal to most metals. If
a micro-examination is made of this metal it will be found to contain
globules of copper oxide in the form of a eutectic (Cu-Cu2O). A layer
of crushed coal is then placed on the molten copper, and as poling
continues the copper oxide is reduced and when a content of about 0.04
to 0.08 per cent oxygen is reached the surface of the button remains
level and the properties of the metal are good, in other words
"tough." The lower the oxygen, the higher the so-called "pitch" and
vice versa, hence the name "Tough Pitch." As poling continues past
this point the copper absorbs hydrogen from the furnace gases and when
cast the metal rises on solidification.
These changes in behaviour, micro-structure and mechanical properties
are due to the influence of hydrogen and oxygen on the copper.
----------------------------------------
End quote

The above confirms not only the use of crushed coal but also the
primitive nature of the processes by means of which relatively pure
copper was produced even in the 20th century. Stirring with a piece of
unseasoned wood is a practice which may have roots going back for
millenia.

The quote is a procedure for smelting chalcopyrite ore.

I don't know where you get that from. The opening sentence says very
clearly "In fire-refining copper ... ".

That's a very
different procedure from what is required to process pure native copper.
Apples and oranges.

But then that's not why I quoted the article. I did so to deal with
your rebuttal of the use of a layer of coal to prevent oxidisation.

A bottom pour furnace is helpful, but you really need deoxidizers in
the alloy to prevent severe porosity problems. Tin and zinc are the
preferred deoxidizers. Arsenic also works, but the fumes are deadly.
Lead makes the metal more fluid, and assists in filling out the mold.
None of those are naturally present in the native copper we're
discussing.

Also, as a side note, where is the evidence for coal mining or large
scale charcoal production in the area? You don't get to copper
melting temperatures with a simple wood fire. You need a forced
draft fire with a high carbon fuel.

A good bed of well ventilated charcoal will suffice. One often finds
melted copper in the remains of burned out buildings.

A fully engulfed large building, or a forest fire, can produce sufficient
natural draft to reach copper melting temperature, but you'd need a
forced draft for a simple bed of charcoal. For doing very small amounts
of metal, such as small silver jewelry items, blowpipes would suffice, but
for doing anything on the order of the size of the artifacts we've been
examining, a bellows or blower would be required, and a *lot* of charcoal.

Let me propose that you conduct an experiment. Go to your local "high
end" audio shop and purchase some oxygen free copper "monster" wire
(similar properties to native copper). Now try to melt it in your backyard
barbeque. The insulation will burn off, but I'll be very surprised if you can
get the wire to melt without a forced air draft and *several* loads of
charcoal.

Actually I have carried out that very experiment to replicate damage
seen to 'Monster cable' in a domestic fire. Just for the heck of it I
through some into the base of a Jotul Alpha wood stove. The monster
cable variously melted or sintered into a solid bar of copper. FYI,
the Jotul Alpha is an 'air-tight' stove with the only air entry being
down the face of the front door glass from the top.

Making charcoal is an industrial enterprise in itself. I'm asking is there
any evidence of such activity in the area under discussion? So far I
have seen no reference to such activities. Nor have I seen any reference
to coal mining activity in the area. All that has been reported is mining
of native copper deposits.

That's a very different question from the use of coal to prevent
oxidisation.

I believe we are agreed that only atmospheric casting was within
reach of the ancient Native Americans (or ancient Old World
founders for that matter), so we *should* see characteristic
porosity in any pure copper items they attempted to cast.

Only if they used the relatively pure meteoric copper of Michigan. It
was laikely to be naturally alloyed if it was smelted.

Meteoric copper? Perhaps you're thinking of iron.

Its a term used to describe the copper deposited by contact with
meteoric water. Meteoric water is ground water formed by
precipitation. See
http://www.minsocam.org/MSA/collecto...r/vft/mi2c.htm

The copper we're
discussing is native copper. Native copper is the result of a natural
geochemical leaching process in certain types of rock formations.
It results in extremely high purity copper.

Only in some places.

Now
of course the Old Worlders had the advantage of ores which
did contain suitable deoxidizers. They weren't actually casting
pure copper. But the Michigan copper was essentially pure
native copper.

But it wasn't the only source of copper.

True, there are impure ores present in the region as well. But
there is absolutely no evidence that any of it was mined or
processed prior to the latter part of the 19th century. Further,
the impure ores which are present contain iron and sulphur
as their major contaminants. Those impurities are extremely
undesireable in copper that is to be cast. The ore has to be
smelted to remove those impurities.

No significant amounts of tin, zinc, arsenic, or lead, which
would improve casting qualities, are present in the ores of
the region. So even if the ancients had adulterated their
native copper with these ores, the result would not be an
improvement in the ability to cast objects from the resultant
mixture.

The ancients lacked a scientific understanding of metallurgy,
but they weren't stupid. They proceded by a sequence of trial
and error steps. If they added something, and the result was
worse, they'd quickly understand not to do that again. Since
the Native Americans in Michigan already had access to very
high purity native copper, and any local adulterant they added
would only make its properties worse, I'd suggest that they
quickly learned not to add any adulterants.

Now the situation was different in the Old World. The metalworkers
there had access to adulterants which *would* improve the casting
properties of copper, and they fairly quickly learned to add such
materials to their copper. That's not because they were brighter,
it is simply because they had materials at hand which weren't
available to the ancients of Michigan.

Gary




Eric Stevens

Gary Coffman wrote:

On Mon, 28 Jun 2004 08:52:10 +1200, Eric Stevens wrote:
On Sun, 27 Jun 2004 02:58:26 -0400, Gary Coffman
wrote:
No trick to melting copper. Doing something intelligent with the molten
metal in an atmospheric environment is a different matter. As I noted
previously, casting pure copper is difficult, even today.

But the question is, how pure was the copper.

The native copper we've been discussing is very high purity.
The halfbreed ore does contain silver, but the silver isn't in
solid solution with the copper (copper-silver alloys are difficult
to produce). Instead it is in the form of distinct crystal inclusions
which would melt out and separate before the copper would melt.

In any case, copper can mostly by prevented from oxidising by melting
it under a layer of crushed coal or charcoal. In fact this method was
used for the production of largely deoxised (tough-pitch) copper in
recent time.

A graphite cover was used to prevent oxidation while melting (coal
won't work because of the large fraction of volatiles, charcoal might
be useable). But you also have to deal with the air entrained when
pouring.

A bottom pour furnace is helpful, but you really need deoxidizers in
the alloy to prevent severe porosity problems. Tin and zinc are the
preferred deoxidizers. Arsenic also works, but the fumes are deadly.
Lead makes the metal more fluid, and assists in filling out the mold.
None of those are naturally present in the native copper we're
discussing.

Also, as a side note, where is the evidence for coal mining or large
scale charcoal production in the area? You don't get to copper
melting temperatures with a simple wood fire. You need a forced
draft fire with a high carbon fuel.

For a people
without inert gas shielded continuous casting furnaces, it would be
nothing but frustration.


Don't under rate the cunning of anceint man.

Don't underestimate the difficulty of getting sound pure copper
castings. Low alloy bronzes and brasses (approx 0.5% to 1% tin
or zinc respectively) aren't too bad to cast, high alloy bronzes
and brasses are easy. But casting pure copper is hard, even
with today's technology.

Again, porosity is the problem, and that should show up on
radiographs, as it does for R666 (which certainly shows evidence
of being melted in atmosphere, though not necessarily evidence
of being cast), but none of the other artifacts presented show
that sort of porosity.

See:
http://www.iwaynet.net/~wdc/copper.htm

The 4th and 5th pictures down.

I believe we are agreed that only atmospheric casting was within
reach of the ancient Native Americans (or ancient Old World
founders for that matter), so we *should* see characteristic
porosity in any pure copper items they attempted to cast. Now
of course the Old Worlders had the advantage of ores which
did contain suitable deoxidizers. They weren't actually casting
pure copper. But the Michigan copper was essentially pure
native copper.


Isn't it just possible that you focus too strongly on perfect casting
- the imperfections resulting from casting may not have been a real
big deal to the ancient people.

--
SIR - Philosopher unauthorised
-----------------------------------------------------------------
The one who is educated from the wrong books is not educated, he is
misled.
-----------------------------------------------------------------

Tom McDonald wrote:

Gary Coffman wrote:

[..]
As I mentioned previously, surface blisters are not what we're
looking for in terms of the porosity characteristic of pure copper
casting. What we need to see is a foam of microscopic bubbles,
and clusters of tiny visible bubbles deep in the metal on the
radiographs. That's absent from the other radiographs on the
site.

Yes, that's why I was interested in your take on R666/55786.
If there were other good examples of melted copper, I'd have
expected that the web site would have presented them.

IT DOES!! It has been pointed to several times already. Your recent
posting is regurgitating what you have posted before. An apparent
casual visual inspection by the Museum curator, nothing more. Here is
the URL again - and don't forget to scroll down a bit!!

http://www.iwaynet.net/~wdc/copper.htm

As it is,
it looks as though I'll have to dig for other examples that
might show casting.

Listen if the seriousness of your "looking" is equal to your looking
on the web site - give it a miss. You wouldn't see anything anyway.

--
SIR - Philosopher unauthorised
-----------------------------------------------------------------
The one who is educated from the wrong books is not educated, he is
misled.
-----------------------------------------------------------------

Tom McDonald wrote:

Eric Stevens wrote:

On Mon, 28 Jun 2004 13:22:35 -0400, Gary Coffman
wrote:


On Mon, 28 Jun 2004 17:38:04 +1200, Eric Stevens wrote:

[..]

While not directly addressing the point, you may be interested in
http://www.lehigh.edu/~inarcmet/papers/jfa022002.pdf

While not Egyptian, and the artifacts analyzed show evidence of
being wrought rather than cast, the chemical analysis does back
my position. The metals being worked were alloys, not pure native
copper.


As I said, it all depends upon what you mean by 'pure'.

Eric,

In the context of this thread, at least its original context,
the copper was native copper in the upper Great Lakes area of
the US and Canada. That copper is typically well over 99% pure
out of the ground, and does not have to be smelted to remove
impurities. If another context is in evidence, then a
definition of the term 'pure' is needed.

http://www.dayooper.com/Networks.JPG

The copper may well be 99% pure - what about the rest? It isn't every
day people find huge lumps of pure copper without impurities embedded
within it. This is the dilemma that people bypass and ignore.

This has a good story about the Great lakes Copper deposits.
http://www.geo.msu.edu/geo333/copper.html

[..]


--
SIR - Philosopher unauthorised
-----------------------------------------------------------------
The one who is educated from the wrong books is not educated, he is
misled.
-----------------------------------------------------------------

On Tue, 29 Jun 2004 05:48:01 GMT, Seppo Renfors wrote:
Gary Coffman wrote:
Don't underestimate the difficulty of getting sound pure copper
castings. Low alloy bronzes and brasses (approx 0.5% to 1% tin
or zinc respectively) aren't too bad to cast, high alloy bronzes
and brasses are easy. But casting pure copper is hard, even
with today's technology.

Again, porosity is the problem, and that should show up on
radiographs, as it does for R666 (which certainly shows evidence
of being melted in atmosphere, though not necessarily evidence
of being cast), but none of the other artifacts presented show
that sort of porosity.

See:
http://www.iwaynet.net/~wdc/copper.htm

The 4th and 5th pictures down.

Those pictures do not show any evidence of the characteristic
porosity copper casting would produce. The single large surface
bubble is a blister, common when the surface of a wrought piece
is overheated. Compare it to the radiograph of R666. The latter
does show the characteristic deep pattern of porosity of an at least
partially melted copper object.

I believe we are agreed that only atmospheric casting was within
reach of the ancient Native Americans (or ancient Old World
founders for that matter), so we *should* see characteristic
porosity in any pure copper items they attempted to cast. Now
of course the Old Worlders had the advantage of ores which
did contain suitable deoxidizers. They weren't actually casting
pure copper. But the Michigan copper was essentially pure
native copper.


Isn't it just possible that you focus too strongly on perfect casting
- the imperfections resulting from casting may not have been a real
big deal to the ancient people.

But the imperfections due to casting pure copper *would* produce the
characteristic porosity which is *not* seen in any of the pieces other
than R666. As I have remarked in other posts, it is possible that this
single sample may have been melted due to a cause other than
deliberate casting, so by itself it is not conclusive evidence for a
copper casting technology, though it is suggestive.

In any event, none of the other objects show the porosity signature
of atmospheric casting. So even if the ancient people found flawed
castings acceptable (and such castings would be weak and brittle),
the lack of porosity is strong evidence that none of these particular
items, with the possible exception of R666, were cast.

Gary

Seppo Renfors wrote:

Tom McDonald wrote:

Gary Coffman wrote:


[..]

As I mentioned previously, surface blisters are not what we're
looking for in terms of the porosity characteristic of pure copper
casting. What we need to see is a foam of microscopic bubbles,
and clusters of tiny visible bubbles deep in the metal on the
radiographs. That's absent from the other radiographs on the
site.

Yes, that's why I was interested in your take on R666/55786.
If there were other good examples of melted copper, I'd have
expected that the web site would have presented them.


IT DOES!! It has been pointed to several times already. Your recent
posting is regurgitating what you have posted before. An apparent
casual visual inspection by the Museum curator, nothing more. Here is
the URL again - and don't forget to scroll down a bit!!

http://www.iwaynet.net/~wdc/copper.htm


Seppo,

As Gary has pointed out, only the item R666 (site report
artifact number), 55786 (Milwaukee Public Museum designation)
shows the characteristic porosity of melted copper; the other
copper artifacts on that page do not. My purpose in mentioning
Alex Barker's observation was merely to have an eye witness to
the artifact in question, to verify that it indeed does look
like a lump of accidentally melted or discarded copper, as
opposed to something that might have been, for instance, trimmed
off the cast after cooling. The other relevant facts about it
seem to have been adequately presented on Connor's web site.


As it is,
it looks as though I'll have to dig for other examples that
might show casting.


Listen if the seriousness of your "looking" is equal to your looking
on the web site - give it a miss. You wouldn't see anything anyway.


So far, at least as presented on this ng, the only copper
artifact that was certainly the result of melting is R666/55786.
The other artifacts Mallery (and Connor) seem to think were
cast either weren't, or don't have sufficient diagnostic
information presented to decide.

Tom McDonald

Seppo Renfors wrote:


Tom McDonald wrote:

Eric Stevens wrote:


On Mon, 28 Jun 2004 13:22:35 -0400, Gary Coffman
wrote:



On Mon, 28 Jun 2004 17:38:04 +1200, Eric Stevens wrote:


[..]


While not directly addressing the point, you may be interested in
http://www.lehigh.edu/~inarcmet/papers/jfa022002.pdf

While not Egyptian, and the artifacts analyzed show evidence of
being wrought rather than cast, the chemical analysis does back
my position. The metals being worked were alloys, not pure native
copper.


As I said, it all depends upon what you mean by 'pure'.

Eric,

In the context of this thread, at least its original context,
the copper was native copper in the upper Great Lakes area of
the US and Canada. That copper is typically well over 99% pure
out of the ground, and does not have to be smelted to remove
impurities. If another context is in evidence, then a
definition of the term 'pure' is needed.


http://www.dayooper.com/Networks.JPG

The copper may well be 99% pure - what about the rest? It isn't every
day people find huge lumps of pure copper without impurities embedded
within it. This is the dilemma that people bypass and ignore.

This has a good story about the Great lakes Copper deposits.
http://www.geo.msu.edu/geo333/copper.html

[..]


Seppo,

Thank you for the urls.

From the second link:

"Michigan’s copper deposits were remarkable for their quality
and purity. Bands of native copper were contained in outcrops 2
to 8 miles wide and of varying depth. The surface deposits first
attracted the notice of Native Americans who dug out the easily
accessible chunks and fashioned copper tools and adornments from
them."

So mining appears to have *begun* where copper deposits were on
the surface. This makes sense, as there was also drift copper
(over a wider area than just the UP mining areas), and folks
early on seem to have selectively used lumps of copper that
needed no processing. While this might not have been an every
day event, it clearly was common enough to produce many of the
copper artifacts in the region.

As to mining the copper:

"They [Indians] dug pits in the ground and separated the copper
from the stone by hammering, by the use of wedges, and,
possibly, by the use of heat. Thousands of hammers have been
found in and about the old pits."

It seems that these folks picked the visible copper out of the
debitage after beating the bejesus out of the rock. That seems
reasonable to me, as there seems to have been quite enough such
copper available to make other methods of extraction unnecessary.

The dilemma you refer to does not seem to exist. Indian people
developed the technology they needed to extract the resource
they wanted. They may have developed copper casting technology
as well. Since smelting wasn't necessary, casting would have
been a stand-alone technology. It wasn't beyond the capacity of
the Indians of the upper Great Lakes; but it also wasn't necessary.

Tom McDonald

Tom McDonald wrote in message ...

Paul,

I'm getting a good free education in this copper business. I
thank you and Gary for your tutelage.

I don't recall reading anything about, for instance, silver
artifacts in the upper Great Lakes area; but this doesn't mean
it wasn't used. I rather suspect that folks were breaking rocks
to extract copper, and may have discarded as debitage the
non-copper bits.

I'll have to look into this, as it would seem that silver might
have been present in large enough amounts that it might have
wound up in archaeological contexts. And, of course, when white
folks came later to investigate and further exploit some of the
copper deposits, I'd be surprised if any silver were to have
been ignored by them.

Tom McDonald

You're missing my point.
Given that casting pure copper is difficult and produces an inferior
product, the casting of copper, simply to save you time forging, is a fool's
errand.( Any craftsman worth his salt would figure this out by the third
try. )
The only good reasons for doing it, are to make a bigger piece of copper or
to clean the rock out.

Eventually, either of these tasks would lead to noticeable alloying.

I would expect this to show up in a full assay of the artifacts.

I've tried to follow this thread, (well, I wandered off when it turned into
a shouting match) and I've yet to see anything that says that all the
artifacts are 99+% pure copper or , in fact, that any were. I am sure that
some testing must have been done, but I am a metalsmith not an
anthropologist, and the relevant research has eluded me so, I have been
unable to ascertain this one way or the other.

Paul K. Dickman

Paul K. Dickman wrote:

Tom McDonald wrote in message ...

Paul,

I'm getting a good free education in this copper business. I
thank you and Gary for your tutelage.

I don't recall reading anything about, for instance, silver
artifacts in the upper Great Lakes area; but this doesn't mean
it wasn't used. I rather suspect that folks were breaking rocks
to extract copper, and may have discarded as debitage the
non-copper bits.

I'll have to look into this, as it would seem that silver might
have been present in large enough amounts that it might have
wound up in archaeological contexts. And, of course, when white
folks came later to investigate and further exploit some of the
copper deposits, I'd be surprised if any silver were to have
been ignored by them.

Tom McDonald


You're missing my point.
Given that casting pure copper is difficult and produces an inferior
product, the casting of copper, simply to save you time forging, is a fool's
errand.( Any craftsman worth his salt would figure this out by the third
try. )
The only good reasons for doing it, are to make a bigger piece of copper or
to clean the rock out.

Eventually, either of these tasks would lead to noticeable alloying.

I would expect this to show up in a full assay of the artifacts.

I've tried to follow this thread, (well, I wandered off when it turned into
a shouting match) and I've yet to see anything that says that all the
artifacts are 99+% pure copper or , in fact, that any were. I am sure that
some testing must have been done, but I am a metalsmith not an
anthropologist, and the relevant research has eluded me so, I have been
unable to ascertain this one way or the other.

Paul K. Dickman

Paul,

Sorry. I got your point, but went off on my own tangent in my
reply. I have gotten the idea that casting copper of the purity
found in the UP mines and drift copper redeposited by glaciers
is, as you put it, a fool's errand when forging was well known
and widely practiced.

Your question about the purity of the copper in the artifacts
is interesting. For my part, most of my sources tend to take it
as a given that the copper artifacts in the upper Great Lakes
area were nearly pure copper. I know that I've read articles
that nail this down, and I'll try to get hold of some of them.

A kind person posted these links to articles in the Central
States Archaeological Journal. You might find them interesting
as they describe a series of experiments by one Joseph Neubauer,
Sr., designed to see how the copper artifacts observed in the UP
of Michigan could have been made. The first link is to an
article discussing the characteristics of the material he used.
The second is to a general introduction to the Neubauer
experiments, and a step-by-step discussion of his process. The
third is an overview and summary of the Neubauer Process. I'm
not a metalworker, but ISTM that most of the information needed
to replicate this Neubauer Process, and by extension the general
method known to have been used by the ancient Indians of the
area, may be found in these articles.


http://www.csasi.org/2003_summer_jou..._poundings.htm

http://www.csasi.org/2003_spring_jou..._poundings.htm

http://www.csasi.org/2004_january_jo...er_process.htm

In the 1947 book, _Indians Before Columbus_, by Paul S. Martin,
George I. Quimby and Donald Collier, all in the Anthropology
Department of the Chicago Natural History Museum, I found this
on page 42:

"Many pieces of copper obtained from burial mounds and from
aboriginal camp sites have been chemically analyzed, with no
trace of any tempering agent ever reported. In fact, the
analyses prove conclusively that the copper in all the specimens
examined is native copper, such as is obtainable without
smelting at certain places in North America today, and that the
aboriginal inhabitants were ignorant of the process of
recovering copper from copper ores or of tempering or hardening
by alloying copper with other metals."

I'll keep looking, however I have yet to come across any good
evidence that the copper artifacts in the upper Great Lakes
region were made from anything but the ca. 99.75+% pure copper,
with occasional incidental inclusions of very small amounts of
other materials.

Hope that is helpful.

Tom McDonald

On Mon, 28 Jun 2004 21:31:53 -0500, Tom McDonald wrote:
Paul K. Dickman wrote:
Much has been bandied about concerning the purity of the copper from the UP,
but you must realize that the same geological process that separates the
copper also separates several other metals at the same time. It does not
place them miles apart but leaves the next to each other, fractions of a
millimeter apart.
for some clarification we will define some vocabulary.

Native copper
This is copper that was left in it's metallic state by the process that
concentrated it. It can be loose, or they can be stuck in a hunk of matrix
exactly as they came out of the ground with other native metals in close
proximity.
Drift copper
This is native copper that has been pounded from its matrix by glacial
action.
Placer deposit
This is a deposit of native metal that has been removed from it's matrix
by erosion (glacial or otherwise) moved from it's original location (usually
by wind or water) and, by nature of its specific gravity and it's resistance
to the motive force has been concentrate with other bits of metal with like
characteristics.

The native copper of the UP is unusually pure. This does not, however, mean
that every piece of rock with copper in it contains only copper.

Below is snip from a site about gold mining in the UP.

.http://www.geo.msu.edu/geo333/gold.html


In June the following year(1846), Houghton’s younger brother Jacob, found a
vein of native copper on the Keweenaw Peninsula which held a small amount of
gold. An assay yielded 10.25 ounces of copper, 1.75 ounces of silver and 12
grains of gold from the 28-ounce specimen



You can see that this particular sample was nearly 15% silver!

Drift copper has had most of the other materials removed by mechanical
action and is usually very pure.

The specific gravities of silver, copper etc. are actually quite close when
compared to sand and placer deposits may contain these in any mix.

Now as to melting.

These native metals are melted for one of three basic reasons.

One, to change it's shape to a finished product
Even today, casting generally produces products that are inferior to
wrought. It is only used when the form cannot economically be produced any
other way,
It is fairly difficult with pure copper, and frankly, if you found a 3
lb hunk of drift copper you would be better off pounding it to shape.

Two, to amalgamate several smaller pieces into one or more larger ones.
The purpose of this is not ,necessarily, to produce a finished product,
but to produce an ingot . Despite copper's casting difficulties, we have
managed to pour ingots of it for almost as long as we have worked metals.
The beauty of the ingot is that if you make it big enough, you can cut
off the bad parts, melt them into the next ingot and pound the rest into
whatever you want.
However, since parent metal is no longer a single nugget of pure copper,
the purity of the casting can be anything.

Three, to separate the metals from the matrix.
This too produces a fine ingot and in the case of Mr. Houghton's sample,
one with 15% silver .


Paul K. DIckman

Paul,

I'm getting a good free education in this copper business. I
thank you and Gary for your tutelage.

I don't recall reading anything about, for instance, silver
artifacts in the upper Great Lakes area; but this doesn't mean
it wasn't used. I rather suspect that folks were breaking rocks
to extract copper, and may have discarded as debitage the
non-copper bits.

I'll have to look into this, as it would seem that silver might
have been present in large enough amounts that it might have
wound up in archaeological contexts. And, of course, when white
folks came later to investigate and further exploit some of the
copper deposits, I'd be surprised if any silver were to have
been ignored by them.

The important point of Paul's excellent post is that if you find
silver *inclusions* in the artifacts, you know that the copper
was never melted (because the melting point of silver is below
that of copper, and the inclusion wouldn't exist if the copper
had been heated to melting).

The Neubauer articles you posted show these silver inclusions in
both ancient and newly made copper tools wrought from Michigan
native copper (also shown are the blisters produced by annealing
and pounding which Conner incorrectly claims are evidence of
casting).

OTOH, Paul is also telling us that if chemical analysis were to show
an actual silver-copper alloy of uniform composition throughout an
artifact, you could then reasonably conclude that it had been molten
at some point.

I should note that the 15% silver assay Paul mentioned is not
the same thing as saying you have a 15% alloy. Assay doesn't
differentiate between inclusions and alloys. So don't be led
astray by that.

If the object is high purity copper (less than 0.5% alloy), doesn't
show characteristic porosity, and/or has silver inclusions, then
you can be very certain it was never melted and never cast.
That appears to be descriptive of all but one of the artifacts
brought into evidence.

OTOH, if chemical analysis of the object were to show it is a
true alloy of copper and other metals (mainly silver for Michigan
native copper), and there is characteristic porosity (because
silver is not an effective deoxidant for copper), then you can
be confident that it has been melted in atmosphere.

Now that's *suggestive* that it may also have been cast, but as
Paul notes, it may merely have been consolidated into an ingot
which was then wrought into the artifact you're examining. And
as I've noted, the melting of the particular artifact which does
show characteristic porosity could have been accidental.

The Neubauer articles provide testimony of large amounts of
small pieces of copper debris, like that produced when smithing
copper in the Neubauer manner, found at native work sites which
would only be there if they were *not* systematically melting and
consolidating small pieces of copper. So even ingot production
seems unlikely.

The more I look at this, the more the evidence piles up that
the Michigan works did not involve casting of copper. Rather,
the evidence, taken together, strongly indicates the Native
Americans wrought native copper in ways likely to be similar
to those used by Neubauer rather than casting them as some
would like to claim.

The reasons I can draw that conclusion are that the artifacts
appear to be mostly pure copper with little or no evidence of
alloying, there are silver inclusions in some of the artifacts
which is proof positive that they haven't been melted, some
have blisters indicative of zealous annealing and pounding
rather than melting, and there has only been one artifact
shown to have the characteristic porosity caused by
atmospheric melting, and that one may have been the result
of an accidental exposure at some point to temperatures in
excess of 1877F (a forest fire is a scenario I suggested to
produce that high temperature).

One further point. *If* casting technology were being used,
we'd expect to find numbers of identical artifacts, since that's
what casting in molds produces. But in fact we don't find numbers
of identical artifacts. We find artifacts of the same *style*, but
differing in dimensions.

Neubauer says, correctly, that's a result of the necessity of
following the copper when working it. In other words, the size
and composition of any particular chunk of native copper
dictates how much you can move and shape the metal, so it
decides what sort and size of tool you can make from it.

I'd also like to reiterate something else Paul implied. The
apparent fact that the Native Americans *didn't* cast native
copper is an indication that they were intelligent and economical
craftsmen. If they had tried casting, they would have quickly
discovered it was an inferior method of utilizing the abundant
raw materials available to them to produce a final product.

They weren't forced to deal with poor ores, they had abundant
chunks of native copper of the appropriate sizes to smith
anything they wished, and had no need to salvage small scraps.
They could simply "high grade" the sites. So the intelligent thing
to do would have been to work the way they apparently did,
smithing instead of founding.

Gary

On Tue, 29 Jun 2004 07:05:25 GMT, Seppo Renfors wrote:
Tom McDonald wrote:
In the context of this thread, at least its original context,
the copper was native copper in the upper Great Lakes area of
the US and Canada. That copper is typically well over 99% pure
out of the ground, and does not have to be smelted to remove
impurities. If another context is in evidence, then a
definition of the term 'pure' is needed.

http://www.dayooper.com/Networks.JPG

The copper may well be 99% pure - what about the rest? It isn't every
day people find huge lumps of pure copper without impurities embedded
within it. This is the dilemma that people bypass and ignore.

This has a good story about the Great lakes Copper deposits.
http://www.geo.msu.edu/geo333/copper.html

As that article notes, 14 billion pounds of copper have been removed
from the area since the ancients were working copper there. Let the
enormity of that number sink in. There was an *awful lot* of copper
there in ancient times, much of it easily accessible from the surface.

Note also, as Neubauer does, that they didn't want "huge lumps".
Copper is difficult to cut with primitive tools (isn't all that much fun
with modern steel chisels). Neubauer suggests that the ancients
would want to start with a piece of about the right size for the
object they wanted to make. At most that would be a lump weighing
a few pounds, in the vast majority of cases it would be a lump smaller
than a hen's egg. Even today, such lumps are relatively plentiful in
the copper belt. They were vastly more so 6,000 years ago before
modern industrial man started extracting copper from the region.

Gary

Apparently on date Wed, 30 Jun 2004 04:08:35 -0400, Gary Coffman
said:

shown to have the characteristic porosity caused by
atmospheric melting, and that one may have been the result
of an accidental exposure at some point to temperatures in
excess of 1877F (a forest fire is a scenario I suggested to
produce that high temperature).

We did come up with the idea that you might get this sort of temperature in a
funeral pyre, because you need that sort of temperature to turn the body to
ash.

Martyn Harrison wrote:
Apparently on date Wed, 30 Jun 2004 04:08:35 -0400, Gary Coffman
said:


shown to have the characteristic porosity caused by
atmospheric melting, and that one may have been the result
of an accidental exposure at some point to temperatures in
excess of 1877F (a forest fire is a scenario I suggested to
produce that high temperature).


We did come up with the idea that you might get this sort of temperature in a
funeral pyre, because you need that sort of temperature to turn the body to
ash.


Martyn,

I now think that it's unlikely that the melted bit was from a
cremation, although it's not impossible. It wasn't found in a
burial context, for one thing.

For another, at least one study of cremations at the Riverside
site appear to indicate that the typical cremation fire was
either not hot enough, or not maintained long enough, to fully
reduce all of the bones. Since cremation temperatures are
typically well below the melting point of copper (by over 300
degrees F, in several references), that scenario seems less
likely that I first thought. I'd go with Gary on this one,
especially as the occupation was aceramic.

If you are interested in following up on this, there is an
article entitled, 'Analysis of a Cremated Burial from the
Riverside Cemetery, Menominee County, Michigan', pp. 383-389,
_An Archaeological Perspective_, 1972, Lewis Binford. Seminar
Press, London. The article prior to that one is a comparative
study of three other Michigan Late Archaic (Red Ocher)
cemeteries, comparing a total of eight burials.

Note: some burials, as with the Riverside burial in the noted
article, include more than one individual. The Riverside burial
included a MNI of 4, three adults and a child.

Tom McDonald

Gary Coffman wrote:

[snip]

The apparent fact that the Native Americans *didn't* cast native
copper

This is a "fact" only if you disregard all evidence to the
contrary, as you appear to be doing.

Yuri.

Yuri Kuchinsky -=O=- http://www.trends.ca/~yuku

A great many people think they are thinking when they are
merely rearranging their prejudices -=O=- William James

Gary Coffman wrote:
On Tue, 29 Jun 2004 05:48:01 GMT, Seppo Renfors
wrote:

Isn't it just possible that you focus too strongly on perfect casting
- the imperfections resulting from casting may not have been a real
big deal to the ancient people.

But the imperfections due to casting pure copper *would* produce the
characteristic porosity which is *not* seen in any of the pieces other
than R666. As I have remarked in other posts, it is possible that this
single sample may have been melted due to a cause other than
deliberate casting,

Not everything that is possible is probable.

Wishing won't make it so.

Yuri.

Yuri Kuchinsky -=O=- http://www.trends.ca/~yuku

A great many people think they are thinking when they are
merely rearranging their prejudices -=O=- William James

Tom McDonald wrote:

Yuri Kuchinsky wrote:

Gary Coffman wrote:

On Mon, 28 Jun 2004 09:04:49 +1200, Eric Stevens wrote:

On Sun, 27 Jun 2004 03:03:50 -0400, Gary Coffman
wrote:

On Wed, 23 Jun 2004 23:46:01 -0500, Tom McDonald wrote:

Eric Stevens wrote:

On Fri, 11 Jun 2004 22:57:04 GMT, (Gary Coffman)
wrote:

But that said, casting pure copper is a bitch.


This from the guy who has just written that the task can be undertaken
by low-skilled workers?

Eric, I read that to mean that casting, in general (as with
iron, silver, bronze, gold, etc.) can be done by folks with
fewer skills than smiths. However, copper appears to present
particular problems with casting that are not so pronounced with
other metals, and which require higher skill levels than would
be required by those who cast other metals.

Exactly, and further, skill alone isn't sufficient to make sound
castings of pure copper. The proper equipment is also required.
Specifically, an inert atmosphere furnace. That technology
didn't exist until the late 19th century.

Just as well the ancient egyptians didn't know that they couldn't do
what they were doing. :-)

So, are you claiming to have evidence that the ancient Egyptians
successfully cast pure native copper?

The metallurgical references I have say that native copper was
extremely rare in Egypt. Almost all of the copper they had was
refined from ores (smelted), and the results were *not* pure
copper. Rather, they were alloys, whether intentional or not,
of copper, arsenic, zinc, iron, or tin. These alloys behave *very*
differently from pure native copper when casting is attempted.

Gary


Well, Gary, the folowing sure seems to imply that the
ancient Egyptian did some copper casting.

[quote]

Ancient Egyptian raw materials: metals - copper, bronze,
iron, gold, silver, lead
http://nefertiti.iwebland.com/trades/metals.htm


copper objects [rather than bronze]:

The objects were generally cast, which is quite difficult to
do with copper because of the formation of gas bubbles
during the pouring of the metal and its shrinking when it
cooled down. Then they were hammered cold to give them their
final form.

[unquote]

Yuri,

Your site tells us that copper ore was what was available, not
native copper; and that it had to be smelted before use. IOW,
it's not clear whether the Egyptians ever had copper of the
purity of the native copper in the upper Great Lakes area. In
addition, the smelting and melting of that copper would more
than likely have resulted in a copper alloy, not pure copper.

Of course, if you have better evidence that shows Egyptians
cast 99+% pure copper, you are welcome to present it here. I
for one would be very interested in that evidence.

Tom McDonald

My main point here is that Gary Coffman is wrong with his
speculations that copper casting was too difficult for
ancient peoples to do.

I'm merely trying to teach Mr. Coffman a few things about
metalworking, as it applies to ancient peoples.

Yuri.

Yuri Kuchinsky -=O=- http://www.trends.ca/~yuku

A great many people think they are thinking when they are
merely rearranging their prejudices -=O=- William James