Silver Alloying: A Beginner's Guide to Sterling Silver Creation

Question
Hello Peter,
We are just new to metalsmithing and are seeking information on alloying silver. We have weighed up our pure silver and added the correct amount of copper to make sterling silver. We are using propane and oxygen to melt the copper and then adding the silver. We are melting it in a silica clay crucible (to which we add a small pinch of borax) and pouring the sterling silver into heated ingot moulds.

When the silver had cooled down we put it into the pickle solution and then into water to rinse. On closer inspection the silver had air bubbles and pockets throughout the piece.

Being new to metalsmithing we have read every piece of information we could get our hands on including this website. I am using a Wescol LPG welding and cutting tip set with wescol regulators and flash arrestors. Could you please tell me what psi or kpa setting I should be using on the gas and oxygen,  and which tip ie: welding or cutting would be best to use for the for the alloying of silver?

Thanks for the great information you provide via the website. Having access to this invaluable resource has given us the confidence to give metalsmithing a go.
Cheers
Mike & Lyza


Answer
Greetings,

Everything you are doing sounds correct, however I've always put all the granules togeethr and melted them as one.

The problem you are having sounds to be the result of two things.
One is that the metal is cooling prior to setting in the ingot mold and secondly the chill plates are too cold.
I would hit the mold with a blackenning flanme prior to the melt and as I am about to pour I usually have the molten metal in the crucible, I drop wee extra borax on top and then swirl the molten metal slightly as I revolve the flame in the oposite direction.....don't be too vigorous though as the metal will fly out.
Once I am happy with the liquidus state, I would bring the crucible to the top of the mold and rest it's lip in place and flick the torch backwards forwards between crucible and mold and then I would continure the heat as I pour in one smooth action.
It's a bit like getting the clutch on a car, but once you've got it you've always got it.

Really can't tell you the setting for gas as I use oxy acetylene which I set at 80/180 and use a cutting tip.

Hope this is of assistance.
Let me know if you need any more inside.

Cheers and good luck, P