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Old June 29th 04, 10:00 PM
Tom McDonald
 
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Default Copper Casting In America (Trevelyan)

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:

"Michiganís 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

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Old June 29th 04, 11:18 PM
Paul K. Dickman
 
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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


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Old June 30th 04, 02:31 AM
Tom McDonald
 
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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
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Old June 30th 04, 10:08 AM
Gary Coffman
 
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Default Copper Casting In America (Trevelyan)

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), Houghtonís 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
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Old June 30th 04, 10:35 AM
Gary Coffman
 
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Default Copper Casting In America (Trevelyan)

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


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Old June 30th 04, 04:47 PM
Martyn Harrison
 
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Default Copper Casting In America (Trevelyan)

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.


  #77   Report Post  
Old June 30th 04, 08:33 PM
Tom McDonald
 
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Default Copper Casting In America (Trevelyan)

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

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Old June 30th 04, 08:53 PM
Yuri Kuchinsky
 
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Default Copper Casting In America (Trevelyan)

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
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Old June 30th 04, 08:58 PM
Yuri Kuchinsky
 
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Default Copper Casting In America (Trevelyan)

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
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Old June 30th 04, 09:03 PM
Yuri Kuchinsky
 
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Default Copper Casting In America (Trevelyan)

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


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