On Sat, 20 Jun 2009 23:35:58 -0700, in rec.crafts.jewelry Ted Frater
wrote:

So what is it? ,

By weight?
or
By volume?

In every alloy description I've ever read, all such measurements are by weight.
Volume comes into play when discussing specific gravity measurments, only in the
noting that it's the weight of a specified volume of metal (the S.G. is the
weight in grams of a cubic centimeter of the material)

Dealing with volume or other, such as atomic, ratios, though, does sometimes
give some interesting insights.

for example, one finds that 18K red golds (75 percent gold, 25 percent copper)
can be very brittle if cooled slowly, because of an ordered array phase that can
form instead of the usual cubic crystal system. That structure makes much more
sense when you realize that if you figure the ratio of metals on an atomic
ratio, it's about 1:1 gold to copper atoms, and the volume of the two metals
ends up having roughly the same 1:1 ratio (though not quite as close).

With that said, it might be worth contacting the British Museum to discuss just
what their figures mean, and why your friend encountered such trouble. It's
also possible, of course, that ancient smiths simply used methods your friend
didn't try. Perhaps it was formed hot, for example...?

Peter