Should I use a store bought refractory rated to 2,600 or 3,000 degrees F.?
This depends on the metal you’re melting. If you’ll only be melting aluminum and occasionally bronze then 2,600 degree rated refractory is fine. If you’ll be meting bronze or iron on a regular basis the higher temperature mix is prefered. The higher the temperature rating of the material the heavier and more dense it is. It also allows more heat to pass through it so the furnace shell gets hotter. Lower temperature refractories are less dense so they have more air spaces which provide better insulation. But they are more easily chipped if struck.
