Re: Copper Casting In America (Trevelyan)

From: Gary Coffman (ke4zv_at_bellsouth.net)
Date: 07/03/04 

Date: Sat, 03 Jul 2004 04:18:32 -0400

On Fri, 02 Jul 2004 13:37:36 GMT, Seppo Renfors <Renfors@not.com.au> wrote:
>Tom McDonald wrote:
>> Seppo Renfors wrote:
>> > Gary Coffman wrote:
>> >>On Tue, 29 Jun 2004 05:48:01 GMT, Seppo Renfors <Renfors@not.com.au> wrote:
>> >>>Gary Coffman wrote:
>> > [..]
>> >
>> >>>>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.
>> >
>> >
>> > They disagree with you as it states "The casting bubble can clearly
>> > been seen...."
>> >
>>
>> Gary showed that the porosity typical of pure cast copper is
>> not present in that artifact. He even explained in just below.
>
>Please point out the "porosity" in this sample:
>
>Two copper pigs:
>http://people.uncw.edu/simmonss/P6030052.JPG

The evidence of porosity is available to the naked eye
in that thin copper flake. There are dozens of tiny bubbles
in evidence, You don't even need a radiograph to see
them. A radiograph or a density test would settle the
matter absolutely, but neither is really needed here as
the sizes and numbers of bubbles already visible are
clear indications of atmospheric melting.

>The casting is obvious in this:
>http://people.uncw.edu/simmonss/LA_1240-1.4.jpg

The large numbers of tiny pits in that piece are suggestive
of porosity, but a stereo radiograph, or a density measurement,
would be required to determine if the piece is actually riddled
with porosity, or if we're just seeing corrosion pitting of otherwise
sound copper (if the object is indeed copper, and not a bronze
alloy).

>Both pictures show melted copper - pre Colombian melted copper! It
>leaves Gary's statements hanging in the air.

Pre-Columbian, or Spanish Conquest? I don't see a precise
dating associated with the individual objects. The web site says
the collection of objects date from the Post Classic and Spanish
colonial periods. Also, the web site says the objects are a mix
of copper, copper-tin bronze, and copper-arsenic bronze. What
evidence do you have that the two particular objects you selected
from that collection are pure copper rather than bronze?

>However if one considers that "bubbling" has been claimed to be caused
>by "overheating" in a annealing process - then it is saying "melted"
>at the same time, as it cannot bubble UNLESS a portion of it is
>melted. Also "welding" requires the melting of the metal - or so
>goddamned close to it that the friction heat generated by a blow on it
>does melt the metal.

You're wrong on both counts. Copper is a malleable, ie plastic, material
even at room temperature. At annealing temperature (500F or greater)
it is much more so. Bubble gum need not be molten for bubbles to be
formed in it, neither does copper. And while copper can be welded, in
an inert atmosphere, by melting, it can also be welded at lower temperature
by pressure.

>Those are two logical examples of melting occurring - the knowledge of
>melting copper existed. It beggars belief that scraps and off cuts
>were NOT melted when the process must have been known to them. That
>people suggest they would rather go and do hard manual labour another
>day to find a piece "just right" for the job, when it is right there,
>right now, right before them. All they have to do is melt it into one
>lump.

And wind up with a porous lump of no use to anyone. Really, you haven't
absorbed anything anyone has been telling you about the atmospheric
casting of pure copper.

>The implied suggestion they would rather do the hard labour, and not
>proceed with the easier option available immediately to them, isn't
>consistent with known human behaviour.

That's your interpretation. But since your interpretation is wrong, your
conclusion is also wrong.

Gary

Relevant Pages

  • Re: Copper Casting In America (Trevelyan)
    ... > The evidence of porosity is available to the naked eye ... > in that thin copper flake. ... There are dozens of tiny bubbles ... Fahrenheit is a long ago discarded temperature measure here and it is ...
    (sci.archaeology)
  • Re: Copper Casting In America (Trevelyan)
    ... > The evidence of porosity is available to the naked eye ... > in that thin copper flake. ... There are dozens of tiny bubbles ... Fahrenheit is a long ago discarded temperature measure here and it is ...
    (sci.anthropology)
  • Re: Copper Casting In America (Trevelyan)
    ... > Virtually all of the evidence presented to date in this thread is ... > against casting of ancient Michigan native copper artifacts. ... We see TWO artefacts being claimed as being cast - one being conceded ...
    (sci.archaeology)
  • Re: Copper Casting In America (Trevelyan)
    ... > Virtually all of the evidence presented to date in this thread is ... > against casting of ancient Michigan native copper artifacts. ... We see TWO artefacts being claimed as being cast - one being conceded ...
    (sci.anthropology)
  • Re: Copper Casting In America (Trevelyan)
    ... Virtually all of the evidence presented to date in this thread is ... against casting of ancient Michigan native copper artifacts. ...
    (sci.archaeology)