My boric acid covered heat treating tray burning off the alcohol. It's not necessary. But if the boric acid is wet with alcohol when it's placed in the forge, it tends to shoot the green flames out the front of the forge.
This shows the benefit of the boric acid coating and what happens when it's not fully covered. The scale affects the surface substantially, to the point where refinishing is needed. So isolation from oxygen is essential. Lots of work to fix this.