Friday, December 31, 2010

Refining Bench Sweeps Experiment.


Often I work in titanium and white gold and yellow gold all at once. So if you filing a triple laminate to shape, say, there is no point trying to save the filings. The go into my bench sweeps bottle. Now the thing that has always hassled me into sending it to the refiners was that the titanium filings and palladium in my white gold is inert to nitric acid.

So doing my home refining number would not work…right? Anyway, I had a nearly full bottle weigh about 500 grams. So I measured out a 100 grams.


Standard kak that comes of any goldsmith’s bench and melting bench. Anyway, from here I put it into a plastic container and poured 70% nitric over it, left it for the night and washed it clean the next morning.

It reacted quite strongly and ate also the silver filings away, which I do not mind.

There were lots of gold dust, filings and little balls left after the nitric had finished reacting, which I have no photo of, sorry. ( check out the home refining link above.)Refining-Bench-Sweeps

From a hundred grams of bench sweeps I got 29.5 grams of alloy after melting. It looked like 14kt and was very malleable as the rolling flat shows. I thought it would have contained so much titanium that it would not a moer be malleable. I also though that the palladium would be dominant in colour because I do a lot of work with 18kt white gold.


Anyway, that bar was then alloyed with 200 grams of copper and shot was made with the subsequent melt. ( check the link )


After the nitric acid has finished reacting it looks just like coffee grinds. Also, it looks like a lot, but after it is melted it weighed 17 grams. So out of 100 grams of bench sweeps I got 29.5 grams of ‘overall alloy’ and after doing the 5 to 1 copper burn I got 17 grams of gold that is very close to fine.

However, this gold is not fine gold. Close, but not quite. In between 23kt and 22kt, I’d say. So I refined the whole 500 gram of the bench sweep bottle, and forgoing in the process my silver and palladium content.


I have written 85 grams fine because I calculate that is the amount by weight in the 22kt pictured.

So now, what I wonder is what happened to the titanium and palladium in the bench sweep dust? For sure there was a lot of titanium sparkles when I melted after the first acid burn, but I figured that some titanium would have sort of diffused into the gold while it was being melted.


And I know that there are alloys of gold/titanium that make the gold much harder, but apparently not in this case. I remember one alloy with titanium called Span Gold, I think, that the CSIR in South Africa was working on. Micro amounts of titanium giving fine gold a hardness of 18kt gold or some such.

Here the bar that is pictured above has been rolled down to .01mm with out annealing or cracking. So it’s malleable. And the palladium in the bench sweeps? Frack knows.

Obviously Hans’ rocket science needs more altitude to understand the finer points of metallic chemistry………

My curiosity says that I must take a small amount of 22ct and re refine it with the 5 to 1 copper . Then check out the difference.

But I am gatvol working with nitric acid. It’s a real bitch to work with.


A slightly left of center friend sent me this picture of a Black Mamba he took in Botswana.

A probable female in a very angry mood. The two little apparent bumps on the bottom of her jaw line are actually her flattened hood. A Black Mamba will do that when it’s pissed off. The female grows the biggest, ( I say that with no reference to human females) and protects her young vigorously. This one does not look as if she has post-natal depression. Right?

When she bites, you get hurt, same as madam nitric does..

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