Ideally, I want a furnace that can melt glass and iron. That means a furnace that can get to, and sustain, a temperature of 2800 fahrenheit to hit the outer temp of glass. At least for the inner shell you’re going to want to be able to withstand 3000 degrees. As temperature drops off, less extreme materials can be used.
I’m planning on an inner shell of 1.5″ of Kast-o-Lite 30 (3000 degrees), possibly mixed with foam/sawdust for additional insulative value if the test cast works out, surrounded by 2″ of Inswool 2300. The insulation goes into a pair of welded steel ice buckets that I found at target. More volume than a steel pail (if you can even find them these days!) and lighter. Remember, the bucket only needs to be strong enough to lift the refractory and protect it. The heavier it it, the bigger the pain in the butt it’s going to be to lug around.
Next up is the burner. While I have access to oxy-acetylene, and it’s damned hot, it’s not exactly friendly on the pocketbook. Thankfully, several enterprising home foundry guys seem to have perfected the cheap, but good, propane burner.
Ron Reil has a lot of good information but not organized well. After a lot of searching, cross-referencing other people’s attempts (mini-mongo) , and reading an excerpt of Michael Porter”s new book I came up with my burner design, which is ultimately a poor man’s T-Rex burner. More about this will be discussed in its own section.
In addition to the furnace (insulation) and burner (heat source), we’ll need a propane tank, tunable regulator (0-30 psi), and a long hi-pressure propane hose to connect the tank/regulator to the burner for safety.
Follow the progress and get links to theory, experimentation and results at The Kcrucible Furnace page.
*** Note that I take no responsibility for replication of anything I’ve done. Be safe and if you’re not sure about something, then stop now. ***