Driving heat across the cooking floor

[cbakken]

Re: Driving heat across the cooking floor

Hi

The diameter of the floor is about 38". The floor is composed of 3" deep fire brick, beneath which there is a concrete pad (but no insulation). The dome is a layer of fire brick, on top of which was plastered about 3" of concrete/vermiculite, on top of which is a layer of decorative stone. After about three and a half hours of firing, the dome itself begins to feel warm to the touch.

I don't have a thermometer, but I fire the oven for about an hour before making pizza. I measure by putting my hand toward the dome and when I cannot count to "one-one thousand," I estimate it's around 700 degrees.

Let me know if that sheds any light on the issue. Thanks for your response.

Goatboy

[cbakken]

Re: Driving heat across the cooking floor

....when I say that the dome begins to feel warm to the touch after 3. 5 hours of firing, I mean on the exterior of the dome, of course. I wouldn't be foolish enough to try touching the whitened interior!

[oventhusiast]

Re: Driving heat across the cooking floor

Sounds to me that the concrete floor under the firebrick is wicking away the heat. Anyone else agree with that?

[dmun]

Re: Driving heat across the cooking floor

Sounds to me that the concrete floor under the firebrick is wicking away the heat. Anyone else agree with that?

Absolutely. Having no insulation underneath means a hot slab and a cold cooking floor. Unfortunately it's not an easy fix. You can build the fire in the center, and rake it over at the last minute before putting the pizza in, but that won't keep it hot. It may also be too hot, charing the bottom before the cheese bubbles.

How's your floor mounted? could you lift the bricks and sneak in a layer of cal-sil sheet insulation? that would give you a little less room in the oven, but it's better than an oven that won't cook pizza.

[jwnorris]

Re: Driving heat across the cooking floor

Absolutely. Having no insulation underneath means a hot slab and a cold cooking floor. Unfortunately it's not an easy fix. You can build the fire in the center, and rake it over at the last minute before putting the pizza in, but that won't keep it hot. It may also be too hot, charing the bottom before the cheese bubbles.

How's your floor mounted? could you lift the bricks and sneak in a layer of cal-sil sheet insulation? that would give you a little less room in the oven, but it's better than an oven that won't cook pizza.

I agree that the lack of underfloor insulation is the problem. Hopefully you can get the floor bricks up.

While two inches of insulation would be preferable, at least an inch will improve things a lot.

J W

[cbakken]

Re: Driving heat across the cooking floor

Alas, I don't think I can raise the bricks without demolishing the whole floor and dome. Obviously insulation underneath the concrete slab won't do any good, right? I'm attaching a photo of the oven for the curious.

http://www.fornobravo.com/forum/phot...ndex.php?n=806

I'm going to try more agressive firing and recharging of the floor between pies tonight. And I'm roasting a duck (the relatively cold floor is actually conducive to good roasting, I've found) and making cassoulet. I'll see if that helps at all.

Thanks for all your comments. Any other ideas, beyond rebuilding the stove?

[Acoma]

Re: Driving heat across the cooking floor

Uno, are you sick? I know you have a good idea on this dilema.
Would you guys agree about CB using SuperIsol underneath? Some type of insulation below seems to be his only solution, unless he rebuilds. Heat will never be maintained otherwise.

[dmun]

Re: Driving heat across the cooking floor

You could try putting the thick pink foam from HD under your slab. It can't hurt and it might help.

I really like your oven by the way, What is that, a cut 12 inch flue tile for your entrance?

[cbakken]

Re: Driving heat across the cooking floor

Yes...a cut flue...plus a little extra wedged in there for a few extra inches width. I'll try the insulation underneath and see if that helps. Thanks!

[cbakken]

Re: Driving heat across the cooking floor

What if I cannot feel any heat under the slab (you see from my photo that I can check that easily)? Is it still worth insulating?

[dmun]

Re: Driving heat across the cooking floor

You know, my oven has two inches of refractory block insulation underneath,



and when I get a big or long fire in it, I can feel warmth underneath the support slab. Are you sure you're building a big/long enough fire?

[dalucca2003]

Re: Driving heat across the cooking floor

I agree with Dmun. I used Super Isol and almost 6 inches of structural concrete and I also feel some warmth from a big or long fire. I would first try and get a nice fire going somewhere in the 900 degree plus range for a couple of hours and then see. You should then feel warmth under the hearth especially if you are not well insulated under the cooking floor.

[Acoma]

Re: Driving heat across the cooking floor

CB needs to maintain the heat too. Since he has no floor insulation, this should get addressed first. No?

[cbakken]

Re: Driving heat across the cooking floor

Amigos

I made a more aggressive fire last night and recharged the floor between pies more fastidiously, which made a big difference.

As for heat under the slab: to my surprise, after between two and three hours of heavy firing, I did feel some warmth under the slab (where I store my wood....see photo). It was just that, "warmth," but I'm going to insulate under there tonight since any lost heat is still lost heat. Thanks for all your suggestions. I think being more concientious about my fire is making a difference. Also, it's a new oven and I think I'm still learning what it's capable of doing.

I'm making that cassoulet tonight with the duck I roast in the oven last night. I'll be flatulent tomorrow....which is surely more information than you all needed....

Cheers,

CB

[KISS4me]

Re: Driving heat across the cooking floor

Great thread. I should have checked this out before I extended my pizza cooking from the family to a group of people. Having to bring the pizzas after the first 2 waves to finish in inside oven because wood oven wasn't cooking bottoms was a tad embarrassing. I have been meaning to get back on-line for yonks since completing my oven in September too.

I now know to get a bloody raging fire going (to plasma), rip some coals out and push to side with fresh wood for cooking flame. Too easy!

Is it possible that washing the firebricks with a wet mop cools it down too much?

Steve