(Frequently Asked Questions.)

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Crucibles, homemade or store bought?

The group consensus has been to buy them.
While it is possible to make ceramic (refractory) crucibles, they don't cost much and your time is better spent casting metal.

There is also some concern that homemade crucibles may be more failure prone. Crucibles should be considered as consumables as they have a lifespan until failure. This lifespan can be enhanced by proper handling. For example temper before first use and anytime they have been sitting for a while, and protect them from thermal shock, as well as impact damage. 

It is a good idea to keep your crucible in the furnace most of the time. For example, between pours return the hot crucible to the hot furnace. And when finished for the day, leave the crucible in the furnace to cool slowly. The next day you can store it someplace else, if you want.

Also, never allow metal to solidify in a crucible, as it will expand on reheating and may break the crucible.

A lot of people will make steel pipe crucibles for aluminum and lower temp metals. These work OK, but will scale if overheated and most agree they should be coated with ITC 100 or similar to prevent iron contamination of the melt.

Cast iron is a better choice than steel for a metal melting pot as it doesn't scale.

It isn't a good idea to use steel or cast iron for metals that melt at temperatures above aluminum because, as you heat the pot, it loses strength.

Remember, all crucibles will eventually fail, no matter whether they are store bought or homemade. Always handle molten metal as if the crucible is in danger if imminent failure.