After buying a crucible for melting metal it needs to be prepped. A crucible is a small porcelain dish that can withstand massive amount of heat so that you can melt metal in it. Depending on the crucible and your intended use different kinds of prepping may be needed. I am prepping my crucible to do small scale silver casting for cuttlebone casts.
I have taken the unused crucible out of its holder
The first step is removing the crucible from the holder. The crucible that I bought through Amazon came in a predesigned holder. I unscrewed the holder and placed the crucible on top of a honeycomb heat protector. This will protect my workspace from a burn mark, which the crucible will leave once it has been heated.
I then filled the crucible with flux and turned on my torch. I am using a larger torch bit then I would use for soldering because I need more heat. After the torch is on and adjusted to a high heat I evenly apply the heat to the top of the crucible. This will take some time because the crucible is designed to absorb heat. As I move the torch in even circles eventually the flux starts to burn off. Keep applying the heat until the flux forms into a glassy surface. If necessary turn off the torch and add more flux.
This glassy surface will help keep the metal from sticking to the crucible. When you pour the metal for casting this prep work will make a big difference. This task doesn’t need to be done every time before you cast. When you cast in the future you will add more flux to clean the metal and some if it will help coat the crucible. You may have to do this again if it looks like most of the coating has worn off, but this is rare.
After a few casts the flux will turn a dark red color
Usually I would use dry flux and not wet flux to coat the crucible. But since I only had wet flux I used it and it did the job. Because the flux is suspended in fluid it will just take a little longer for the flux to burn away. Remember to wear goggles because flux is made of glass and can easily hurt your eyes. Watch the above video for a demonstration of how to prep a crucible for casting.
After you use the crucible for casting a few times the flux coating will turn a dark red to maroon color. This is completely normal and fine. I do not know why the hard flux changes colors but I think it has do with the fact it has been oxidized or is taking in the oxidized material of the silver.
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