I recently burnt out my lemel (prior to sending it to the refiners)
in a large Nescafe container, some thing I have done many times
before, but alas the company must have altered the material they make
there containers from because this time it melted leaving me with a
alloy of 1500 grams of filings (mainly eighteen carat) and some other
meta1 in a lump of material melted into the fire brick base of the
kiln, the gold visually mixed in side it. In my endeavours to
remove the gold from the overall mass I placed it in a large carbon
crucible hoping to melt the gold and granulate it, but again No good !
Instead I have a crucible with a mess of material inside that appears
to be able to absorb any heat I subject it too, as I am sure that
many jewellers use these types of containers to do this job I may
have happened to them and if so can any body help me Russell
McColough in Sydney Australia
G’day Russell; It seems to me that you may have used an aluminium
can to melt your lemel. I suggest that instead of using a
crucible with steep sides you use a dish shaped crucible and heat it
directly with a torch flame which has an oxygen boost, even if you
have to do it in small amounts. When you have a molten pool,
sprinkle the surface with a little borax, then pour it slowly from a
4 ft height into a bucket of cold water… Now take the granules so
produced and simmer them in hot washing soda solution. which will
dissolve some of what aluminium may be there… You may have to
repeat this operation a few times, but you should finish with much
purer gold. Cast it into small ingots and then send it to a
refiner. Heating a tall crucible with a gas torch won’t help much
as it is difficult to get enough heat. Such crucibles are better
suited to a kiln.
I also suggest that the simplest treatment for precious metal
filings is to mix the filings with plenty of borax to a very stiff,
thick paste with water, then melt in an open dish crucible if you
haven’t a kiln
Cheers for now,
John Burgess; @John_Burgess2 of Mapua, Nelson NZ