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  #51   Report Post  
Old June 28th 04, 07:07 PM
Gary Coffman
 
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Default Copper Casting In America (Trevelyan)

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

  #52   Report Post  
Old June 28th 04, 07:14 PM
Gary Coffman
 
Posts: n/a
Default Copper Casting In America (Trevelyan)

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
  #53   Report Post  
Old June 28th 04, 07:22 PM
Gary Coffman
 
Posts: n/a
Default Copper Casting In America (Trevelyan)

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
  #54   Report Post  
Old June 28th 04, 07:26 PM
Tom McDonald
 
Posts: n/a
Default Copper Casting In America (Trevelyan)

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
  #55   Report Post  
Old June 28th 04, 08:50 PM
Yuri Kuchinsky
 
Posts: n/a
Default Copper Casting In America (Trevelyan)

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


  #56   Report Post  
Old June 28th 04, 09:20 PM
Yuri Kuchinsky
 
Posts: n/a
Default ancient copper casting outside N Am ( Copper Casting In America(Trevelyan)

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
  #57   Report Post  
Old June 28th 04, 09:25 PM
Tom McDonald
 
Posts: n/a
Default Copper Casting In America (Trevelyan)

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
  #58   Report Post  
Old June 28th 04, 11:49 PM
Eric Stevens
 
Posts: n/a
Default Copper Casting In America (Trevelyan)

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

  #59   Report Post  
Old June 28th 04, 11:49 PM
Eric Stevens
 
Posts: n/a
Default Copper Casting In America (Trevelyan)

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

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Old June 29th 04, 12:06 AM
Tom McDonald
 
Posts: n/a
Default Copper Casting In America (Trevelyan)

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


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