hihoag said:
Any recommendation on where to purchase the crucibles, clay melting dishes and torches?
You should have success by shopping with jewelry supply houses. Clay dishes are very much a part of the jeweler's bench, as are torches.
What are the keys characteristics to look for in each?
Jeweler's torches are generally the Hoke type torch (named after the father of the book's author), so see what they offer. Get the largest one you can find. They used to sell one that very much resembled a rose bud for a welder's torch, but I have not found one in my recent searches. It could be that it is no longer available.
As for the melting dishes, they used to be made of a light brown clay, and were very unstable. The newest ones, which used to be marketed by Vigor, were almost snow white, and fairly thick. They are obviously molded, not free formed. They used to be available in sizes, including one in which you could easily melt ten ounces of gold. If you season them correctly before they are placed in service, they don't crack, and will last a long time.
When would you use a clay melting dish vs the crucible, purely volume?
Pretty much. A crucible generally does not lend itself well to torch melting. In order to get the heat where it's needed, you must plunge the tip deep in the crucible. That's not a good idea because you overheat the torch tip, risking melting. A dish, by sharp contrast, is shallow and wide, you can work the surface of the material easily.
I melted even large volumes (hundreds of ounces) of gold by torch. I could have the job done before a furnace came up to heat. The picture, below, is gold that was torch melted (I trust everyone is tired of seeing this picture, but it's great proof that the system mentioned works well).
Harold
