Since I started knifemaking, I have wondered how to make a forge that would be simple enough to build with a few tools, and still be effective enough for blacksmithing and knifemaking. Ive looked at forges, and forge designs all over the internet to get ideas for what has worked for others.
One common forge design I saw was to cut open a 20lb propane tank or freon tank to use as the forge shell, then line the shell with a fiberglass insulation. This insulation is sold under different names like “Durablanket” and “Kaowool” or “Inswool”. The insulation is manufactured in blanket form, and is typically used to in the construction of blacksmith forges and furnaces. A hard ceramic coating is applied to protect the soft insulation from being torn, but also to create a barrier against airborne dust from the insulation.
I used the same design, but with a small 16 oz propane bottle. The forge heats up pretty quickly and works perfectly for forging knives and other small blacksmithing projects.