Here is the video of the foundry I want to make. We know it melts aluminum but would it melt copper or glass?
I don’t know if that foundry design would get hot enough to melt copper, but other YouTube links on the right side of the screen explain how to build a foundry to melt copper. So if you want to melt copper, why not start with a different design?
Copper melts at about 400C hotter than aluminum. Using hardwood charcoal with the right size pieces it should work for copper, it’s basically the same as copper/bronze age foundries.
No, plaster cannot take the higher temperature. You will need a different design.
The plaster will degrade rapidly, but it may still work. Homebuilt iron foundries lined with refractory materials may need to be relined after each firing. However, using refractory cement makes much more sense than plaster for melting copper. Fire bricks, or even red brick construction with refractory cement is a better approach.