How to get a "clean" silver button

[arie_pk]

Hi to all

With the help of you guys, I managed to refine a few batches of silver, over all around 1 kg of silver cement. I finally started to melt today in to buttons. I am using a map/oxy torch and melting in a regular crucible with a little borax. Once the buttons cools off a bit, i pry with tweezers from the crucible and let it cool. The problem is the button is partly covered with borax, which is very hard to remove when cold. Is there any way to get clean smooth buttons without the borax residue, or any method to remove the borax.

Thanx

 

[Lou]

Well, one is not to use so much borax, or melt it again and cast it as shot.

Your other option is to give your silver a boil in dilute (as in 5% by weight) sulfuric acid, this will remove any borax on the surface. Do not use anything more concentrated than that else it may dissolve your silver.

Lye also works, but I tend to steer clear of boiling any caustic solution.

 

[Harold_V]

You can achieve excellent results by pouring the fluxed silver to a cone mold. The flux will accumulate on the top surface, which will be relatively small. When it has cooled, the flux will often chip off with a single blow of a hammer. It can then be re-melted in a crucible with no flux, and poured to a mold that is blackened, yielding a clean ingot (or button).

I advise fluxing the cement silver as you're doing. A great deal of contamination is removed in the process, and the silver flows much better. It pays to recycle the flux, for it often contains prills.

Harold