This is one way to build a foundry out of a 20lb propane tank.

I got my supplies from Smith-sharp fire brick supply in Minneapolis.
I cannot recommend any sources online because I didn’t use those products.

I used Mizzou refractory cement. It’s the strongest you can find. It was $50 for a 50lb bag where I got it at Smith-Sharp Fire brick supply.

In the video I used z-wash. If I was going to build it today I would use greenpatch-421