losing heat fast on the floor...

[junglepizza]

e recently had an oven built down here on the Pacific coast of Mexico where traditional mud ovens have been used forever. It is a large oven - diameter of the floor is 63 inches and height of dome is 60 inches. Our opening is about 27.5 inches by 12 inches and there is not a chimney but there is a small circular opening about 6 inches in diameter on the side just above the floor. Once we get the oven up to temperature we have been splitting the fire into two and moving to both sides of the oven. The problem is that the floor in the center for cooking is dropping in temperature very quickly and the pizzas are not crisping up on the bottom. Any suggestions on how to control this better?

[Acoma]

Sounds like you don't have any insulation below. What do you have for the hearth? What kind of bricks? Did you use any insulation below the bricks? If clay, did you mix lots of straw, clay mixture for insulating factor? There have been a few clay builders on this forum that could help out. How about a photo of this behemeth? Why so big? Lots of questions, sorry but many will need to know so that the advice is more clear.

[james]

Robert,

How did the hearth on your oven keep up with pizzas? Were you able to keep the hearth as hot as the dome? How big was your fire?
James

[Acoma]

James, mine kept up good. I would throw a fresh log in every 15-20 minutes for heat to be maintained. I would keep the hearth in the 800's and it would maintain for several pizzas, 4-5. It would then cool to 700's since the pizzas were always in the same general area, but I would then rake the coals over the area for a few minutes and it would shoot up the the 800's again. As we know, a few pizzas suck up the upper hearth brick heat, but with saturation of the brick, placing some coals over the area bring the temp right back up. This is what I would do when I needed to keep the heat in the 800's for best desired appearance, balance of doneness throughout.

As for the dome and hearth, the dome would stay in the 800's to 900's. The hearth would only loose heat from semi cooling due to pizza's.

As for fires, getting the fires going initially was progressive with flames and heat. After an hour I would get an inferno going. This takes me 2.5 hours to get the dome white and saturated. Afterwards, I keep a log or two (depending on size) in there, running up to the top. Again, this is done every 15-20 minutes or so when doing the pizzas.

When done with the pizzas, I know I have great retention of heat becaue the next day the hearth is in the 400's, with the dome in the 600's.

[james]

Not bad!
James

[gjbingham]

Junglepizza,
Did you or your builders use any insulation below the floor of the oven? I believe the traditional mud ovens did not use insulation under the floor, so even if you got the thing to 800 degrees, it would loose its heat to the surrounding substructure.

If there was no insulation put under the floor, I'd either add an additional layer of firebrick on the floor - in essence, build up to increase the heat retaining abilities, or work on a technique with the fire to surround your pizza with the coals on all sides - as close as possible. Perhaps even raking the coals back across the floor for 5 -10 minutes after each pizza, then clearing and brushing it again just before the next pizza. Its a big oven so it may just take a ton of wood to get the thing hot enough to retain the heat necessary to keep the floor hot.

A picture might just solve the whole question. The chimney set-up sound unusual. You might be loosing all your heat out the pipe.

[jengineer]

hey why are we busting this up again?

there is a longer thread on this at
http://www.fornobravo.com/forum/f6/l...loor-3832.html (losing heat fast on the floor...)

If this sub heading is a better place for this discussion then maybe James could move the linked thread to this section...

[gjbingham]

Ha! I've read way too many posts. This didn't even look familiar. Good catch on the duplicate!