Metal Casting Zone

I am looking for some comments on crucible durability. I have used small fused silica and found them to be about indestructible, heck I even dropped one in a bucket of water while pouring silver into it for shot form. I was wondering if a larger one say 3 1/2" tall would be as tough?

Never assume a crucible is indestructible. They can all break, usually at the worst possible moment. Given that, I have heard that fused silica crucibles are pretty tough, I'm sure that it would work fine and last a long time. Probably a good silicon carbide crucible would be cheaper and last almost as long. If you have a cheap supply, have at it. I would think that a small one would have less of a problem with thermal gradients over the crucible than a larger one, and where it was completely submerged all at once there wasn't much difference to cause cracking. Commercial crucibles have a reasonably long working life if taken care of and stored properly.

I use it with new crucibles for CoCr alloys, pour in,swirl,pour out. The spray nozzle gets clogged very quickly and IMO is a waste of time. Then the crucible is pre-warmed before casting. It helps to keep the crucible from acquiring a build up of slag/residue. The rub-off is nothing to worry about. Don't finger it, leave alone. It works but I'm not certain how much benefit there is. Maybe someone else will have an answer.