Building a 30 minute oven

[monader]

Im in the middle of building a 31 inch oven with a dome hight of 15.5 inches. My question is how thick should my base and dome walls be to be able to get the oven up to temp within 30 minutes? I was looking to go as thin as possible ~2 inch dome to speed up heat time, as well as maybe doing half the floor in soapstone.

Would 4 inch of 7:1 / 10:1 perlcrete below the floor and around the dome be enough insulation?

This is my first build.

[david s]

If you want that kind of heat up time, go and buy a stainless steel oven. It is not possible to heat up a refractory oven to pizza temperature in 30 mins. Firing an oven with a raging fire from light up is also likely to cause damage to the refractory from excessive sudden thermal expansion. Some manufacturers of refractory ovens claim that their ovens can cook after 20 mins, but they won’t have reached proper pizza temperature.
2" thick inner dome is as thin as you can go without risking too much lack of strength IMO. Casting the dome into three sections and the addition of 2% stainless steel needles would help but both make construction more difficult, expensive and time consuming.

[monader]

The FB Casa80 Home Pizza Oven Kit says 30 minutes "heat up" time, (https://www.fornobravo.com/product-s...zza-oven-kits/) . Are you saying that kit doesnt really get to pizza temp in 30 minutes?

About stainless steel, what if i put a stainless steel liner inside the oven walls, or hang a steel plate from the dome ceiling, would that help get the temp up quicker?

[wotavidone]

I have a 29.5 inch dome made from 2 inch bricks. I chickened out on the stability side of things and coated that with 3/4 to 1" of homebrew mortar with chicken wire reinforcing.
I can get the dome white in 45 mines, and then cook a pizza straight away, BUT:

The bricks are barely warmed up internally.
Recovery between pizzas is therefore poor, you have to reheat with a lot of fire, there is not enough heat stored in the bricks.
Heating up so quickly increases the risk of cracking, because the external surface of the oven is so much lower than the internal surface, so the inside is expanding more than the outside, creating tension that can pull the oven apart.
To be honest, a slower warm up doesn't use significantly more timber and gets better results.
A roaring, big scary fire will get more heat into the bricks in a shorter time, but also puts more of the available BTU's up the chimney.
As far as midweek pizza goes, even with a 1 to 1 & 1/2 hour warm up I find I can light the oven, and barely have to wait after I've poured a glass of wine and done the pizza prep.

[monader]

I have a 29.5 inch dome made from 2 inch bricks. I chickened out on the stability side of things and coated that with 3/4 to 1" of homebrew mortar with chicken wire reinforcing.
I can get the dome white in 45 mines, and then cook a pizza straight away, BUT:

The bricks are barely warmed up internally.
Recovery between pizzas is therefore poor, you have to reheat with a lot of fire, there is not enough heat stored in the bricks.
Heating up so quickly increases the risk of cracking, because the external surface of the oven is so much lower than the internal surface, so the inside is expanding more than the outside, creating tension that can pull the oven apart.
To be honest, a slower warm up doesn't use significantly more timber and gets better results.
A roaring, big scary fire will get more heat into the bricks in a shorter time, but also puts more of the available BTU's up the chimney.
As far as midweek pizza goes, even with a 1 to 1 & 1/2 hour warm up I find I can light the oven, and barely have to wait after I've poured a glass of wine and done the pizza prep.

Thanks for the info, a few questions, have you had any cracks in your oven? I was hoping to increase the floor time by putting in half soapstone, which looks like it can warm up faster, transfer heater faster, and work at a lower temp. How did you cut your bricks into 2"? how long does your oven hold temp? How much long does your dome vs floor take to get to temp?

Fuel for me isn't a huge issue for me, i have a good amount of land with wood that needs to be taking out, im more looking for speed and to not have to clean out the oven as much from burning tons of fuel.

[wotavidone]

I gotta do work stuff. Here is a link to my build. On last page there is an update.
Oven on wheels

[monader]

Nice build, good to hear its still solid. Ill likely be doing something similar with a little less mortar. I think david s is correct, those FB 30 minute claims on the casa are not accurate, from what i hear its closer to 40 and thats really pushing it. Ill have to see what else I can do to speed things up, but wont be expecting 30 min.

Thanks for the info, ill have to post up my build when its finished.