Paul K. Dickman wrote:
In order to illustrate the nature of the porosity in melted copper I put a
few
pictures up.

http://tinyurl.com/3cw7p

The first labeled Casting is a small ingot cast of ca110 copper It started
out
essentially 99.9% fine. The casting method was about as simple as you can
get.
It was melted with an oxy-acetylene torch and poured into an open mold, made
by
scraping a depression into some foundry sand.

The "cocks comb" sticking out in the upper left is not a sprue. When the
pour
was finished the ingot was shaped like a little loaf. As it solidified,
dissolved gasses came out of solution with the metal. As they did they were
trapped by the solidified metal on the outside of the ingot and built up
pressure. Eventually a weaker spot in the surface of the metal gave way and
metal and gas squirted out. Like stepping on a ketchup packet in the
McDonalds
parking lot.

The size of this is indicative of how much gas was dissolved in the metal.
It is
approximately 10% of the original volume of the ingot.

The rough area in the lower left is not indicative of porosity, It is where
the
metal first struck the sand. When it did, it's surface tension was
sufficiently
disturbed to allow it to flow into the spaces between the sand grains.

The second picture, labeled section, shows what this looked in a cross
section
cut at about the base of the "cocks comb"
You can easily see the large bubbles. It also has a large amount of small
bubbles that are visible under a 10 power loupe.
You can see that it looks very similar to the R666 radiograph. However that
piece looks more like a mistake than a deliberate casting.
You can also see that it is not a single round bubble but a miriad of
amorphous
blobs.

The third picture, labeled forgings, shows it's workability.
The lower shot is from the pure copper ingot, You can see it is full of
fractures and tears.
The upper forging is made from an ingot cast from approx. 4% silver-96%
copper.
This ingot exhibited no cocks comb and the forging was made from the entire
ingot, with no waste removed.

The two metals are visually identical, but one casts like crap and the other
doesn't.

If they were casting on any scale, it is not just inevitable that alloying
occurs, it is pretty much a necessity.

If you want to prove casting, stop stroking around with radiographs and look
for alloying.

Paul K. Dickman

Paul,

First, wow. Thanks for taking the bull by the horns and doing
an experiment. I'm reminded of the old story of the horse's
teeth. While a bunch of Greek philosophers stood around trying
to reason how many teeth a horse had, a Roman walked up to the
horse, opened its mouth and counted them. Thanks for the
'counting'.

Second, I'm stroking around as fast as I can with what I have
:-). (Insert joke here.) As I learn more from people such as
you and Gary, I learn what questions to ask. I'm getting to the
point where I have enough information to ask intelligent
questions of the literature and the folks working on the issues.

I will soon be composing an email to some archaeologist in
Wisconsin, at the University of Wisconsin in Madison, and at the
Wisconsin Historical Society. I'll also be looking for
suggestions as to who to contact in Michigan, other than Susan
Martin. Any suggestions as to other questions to ask, or other
folks to contact, would be appreciated.

Third, wow.

Tom McDonald