Just for curiosity. No, I use propane for firing. But I have heard that in older times it was possible to fire porcelain with wood based kilns to 1400 C. How did they attain this ? Special design with the exact air inlet ?
Well, I started out with a charcoal briquette fired furnace with forced air, and easily melted aluminum. I did melt some copper once, but the ash started choking out my air inlet and it cooled back down. I have a "stack melter" that also uses either charcoal or scrap wood, and I've melted aluminum in that too, with forced air. It can be done, but does need forced air with good breathing. If the ash from the wood starts to choke things down, the temp cools and the metal freezes. "We" didn't have propane or other gaseous fuels during the bronze age, so apparently "we" figured out how to sustain 1800* with wood or coal. Roger
I'm not sure what it would take to maintain 1400°C but I know from experience, the natural draft in a 45 gal burn barrel is more than hot enough to melt aluminum.
We didn't have gaseous or liquid fuels in the iron age either. Forced air with charcoal or coke gets as hot as you'd like. When you say wood, you mean unprocessed charcoal. All you o to make a hot wood fire is burn off the moisture and light materials first and then get to converting the carbon to CO and CO2. I brought a bucket of partially used charcoal home from a blacksmith meeting one time and let it sit until I thought it was coal coke. When I used it it burned like coke. Later when I was looking for the charcoal I realized I'd used it but couldn't tell the difference. Now I'm not a good blacksmith but I learned charcoal does burn very well. Forced air is the key to heat with solid fuels just as it is with liquid or gaseous fuels.
I found with charcoal too much air can be an issue, driving the heat away from the melt. The amount of forced air needed to get to brass temps was surprisingly low.
I’m a little late to the conversation but I once lit an open air brush fire of Ironwood that burned white hot and the 6’ diameter 3’ tall pile was so hot I couldn’t stand the heat at 30’ and had to shield my eyes from the light radiation. Spent a lot of time sharpening my weed eater saw blade getting it cutdown and actually seen it rarely throwing sparks as it was being cut. So I’d say it somewhat depends on the wood source but hardwood can obtain fairly high temperatures given the proper amount of oxygen, wood block size and gas flow through the burn media.
Biringuccio's Pirotechnia has drawings and descriptions of reverberatory wood fired furnaces for bronze. Contemporary with Michelangelo. There's an english translation in the public domain.
