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Re: How cheaply can an oven be built?
I have an almost completed [indoor] 36" that is still under US $500. It has a [mostly] clay dome with a single ring of firebrick at the bottom for durability against fuel and tools. I would say that a clay dome is probably trickier than firebrick in terms of longevity unless you know a lot about your local clay. This is my second clay dome WFO so most of the mistakes have been made. Do a prototype if you try a clay dome. Another cost saving measure in my case is because of space restrictions (it's inside a lowish part of a greenhouse) the hearth is only ~20" off the ground and pit in front corrects for hearth height. I have ~8" of perlcrete on top of a 4" slab and used ~10" of perlite in a light clay slip over the dome and am covering that with a thin cob shell.
My first choice would have been a firebrick Pompeii but I don't have enough electrical resources to run a brick saw and don't want to modify my lifestyle enough to do so. My second choice would have been cast refractory dome and even though I live practically next door to where castable and firebricks are made I can't actually buy castable closer than 300 miles away and would have to pay ~$2/lb. in total to have it shipped.
I'm still pushing the 40+ gallons of water out of the dome insulation but have already done pizza at 800+F hearth and dome temps. Dome has gone over 1000F on my non-contact thermometer. Since the dome contains silica it theoretically could spall at 1600F but even the most intense fires (osage!!!) in the first WFO didn't do this. I am also doing some interesting things to capture and control heat from the exhaust flue, hopefully providing heat in the winter and running a large dehydrator in the summer.
I have an almost completed [indoor] 36" that is still under US $500. It has a [mostly] clay dome with a single ring of firebrick at the bottom for durability against fuel and tools. I would say that a clay dome is probably trickier than firebrick in terms of longevity unless you know a lot about your local clay. This is my second clay dome WFO so most of the mistakes have been made. Do a prototype if you try a clay dome. Another cost saving measure in my case is because of space restrictions (it's inside a lowish part of a greenhouse) the hearth is only ~20" off the ground and pit in front corrects for hearth height. I have ~8" of perlcrete on top of a 4" slab and used ~10" of perlite in a light clay slip over the dome and am covering that with a thin cob shell.
My first choice would have been a firebrick Pompeii but I don't have enough electrical resources to run a brick saw and don't want to modify my lifestyle enough to do so. My second choice would have been cast refractory dome and even though I live practically next door to where castable and firebricks are made I can't actually buy castable closer than 300 miles away and would have to pay ~$2/lb. in total to have it shipped.
I'm still pushing the 40+ gallons of water out of the dome insulation but have already done pizza at 800+F hearth and dome temps. Dome has gone over 1000F on my non-contact thermometer. Since the dome contains silica it theoretically could spall at 1600F but even the most intense fires (osage!!!) in the first WFO didn't do this. I am also doing some interesting things to capture and control heat from the exhaust flue, hopefully providing heat in the winter and running a large dehydrator in the summer.
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