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Tom McDonald
 
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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