graphite crucible vs graphite mold?

Is there a difference in composition? I've read on this forum that you shouldn't use a graphite ingot mold to melt gold in a furnace. Why is it OK to melt gold in a graphite crucible? What is the difference?

Thanks, from a new guy.

Clay is used as a binder in most of these crucibles.

The molds usually are just nice, high grade EDM graphite and will oxidize away.

The IECO tunnel bar systems use them, but do so in a nitrogen gas atmosphere to keep the goods shiny.

Lou

Thanks, that makes sense to me now. Really nice to be able to ask these types of questions and get great information back here. Great forum. What would happen if you heated and glazed the mold with Borax before melting gold? Also, can you simply melt gold in a porcelain crucible (such as a Coors) and then pour into a graphite ingot mold? What I'm trying to do here is to refine my own placer gold and then pour 1 gram bars as gifts for the grandkids. Thanks again.

I would strongly suggest keeping Borax and graphite well apart. You don't need it on graphite.

rsmuff said:

can you simply melt gold in a porcelain crucible (such as a Coors) and then pour into a graphite ingot mold?

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Coors porcelain is subject to thermal stresses---very easy to break while being heated, or by cooling too quickly after being heated. I'd highly recommend you avoid using such a vessel for melting gold. Small amounts (up to ten ounces, pure) can be melted by torch using small melting dishes, which lend themselves far better to such activity. A deep crucible is a poor fit with a torch.

What I'm trying to do here is to refine my own placer gold and then pour 1 gram bars as gifts for the grandkids. Thanks again.

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A noble gesture, to be sure, but you'll have no luck pouring small ingots. Gold won't cooperate with your plan, as surface tension gets in the way all too quickly. The smallest ingot I poured (with success) was ½ ounce troy----which looked very much like a tiny loaf of bread. Surprisingly, my ½ ounce ingots turned out better than anything larger, up to the ten ounces that I poured.

Harold