Why are my silver bars comeing out like this?

[Jeff0172]

Hello guys i have a issue i hope someone can help with dor the life of me i cannot pour smoth bars and ive tried everything and they all are ending up like the ones in the photos i useing a electric furnace with a graphite mold with a constant flame on my mold and it is pre heated ive tried mapp and propane with the same results ive even used a second torch to keep on the crucible while im pouring and they still come out like this a deep crater in the middle and cracks all threw it ive end tried not keeping a flame on the mold with the same result any advice would be greatly appreciated

 

[FrugalRefiner]

Silver can absorb somewhere around ten times its volume in oxygen when it's molten. It gives this oxygen off as it freezes, causing "crabbing and spitting". You need to keep oxygen away when melting. Try a graphite cover on top of the melt, to both exclude and absorb excess oxygen. Perfect silver bars can be difficult to achieve.

Dave

 

[galenrog]

Dave is entirely correct. When I first learned, I did not know much about silver, either.

If you plan on selling directly to a large refiner, your bars are fine as they are. If you want to learn how to pour bright, shiny bars, it will take following the advice given by Dave and a few others. And a lot of practice. I do not bother anymore for a variety of reasons.

Have fun.

Time for more coffee.

 

[Traderdoc]

One of the other administrators (in another post) suggested using either charcoal or wax to prevent oxygen being absorbed. Does anyone know how one does this practically? What type of charcoal or wax should be used?

Thanks.