Oven Not Retaining Heat

[Petar. Petrovski]

Hi All,

Sorry I might be entering the wrong conversation, but could someone advise on what needs to be done for my oven to hold the heat better?

I have built it with normal red clay bricks and insulated the dome with layer of ceramic blanket insulation, than a couple of layes of render.For the base of the oven I got 100mm concrete slab and on top of it fire bricks.
I can read about ovens being hot for hours even the following day, but not sure how is that achieved even having fire bricks around the entire dome. I have received some extra fire bricks which I am planning to lay additionally for better heat stirring, but after heating one of those to red I have taken it outside and it was ice cold within an hour .
I read for days and days and can't understand the principal of those bricks as it appears that the people that sell those dont even know how the product works. They explain that they are designed to withstand the temperature but does that mean holding the heat for hours?????
I do apologize again for jumping in to the wrong topic, but I am new to this form and I need to understand where have I got it wrong and is there any way of altering the problem so my oven can hold heat as most wood ovens supposed to?

Thanks in advance
Petar

[SableSprings]

Sorry Peter64 for the additional highjack of your thread...but it is what it is...

Welcome Petar Petrovski! Firebricks are very dense, generally larger and much heavier than clay bricks, and will absorb a significantly larger amount of heat while being exposed to high temperatures (as in active fires & coals). The problem you are having (if you are using real firebricks for the cooking floor) is not with the brick's heat retention, but with lack of insulation between the concrete supporting slab and your oven (primarily the cooking floor). Currently your floor bricks are passing their heat into that slab...and the slab is absorbing it very quickly. That's why your oven "goes cold" within a short amount of time. If you are heating a "real firebrick" side by side with a red clay brick and then setting them outside (on an insulated base), the firebrick will remain hotter, longer (because it has more mass). Another problem you may face, is that newer red clay bricks are currently not fired to as high a temperature as they used to be...so they will very possibly crack and spall as they are subjected to the normal firings of a WFO. (The red clay bricks will also not store as much heat as the firebricks.) In terms of applying a "fix" to your oven, you would need to get some insulation under the cooking floor at the very least. This may be pretty difficult depending on whether you put your cooking floor inside the dome or built your dome on top of the cooking floor perimeter. If you could remove the inside cooking floor firebricks and place a 2" (~5 cm) of ceramic insulation board between the base slab and the firebricks, you would see an enormous gain in heat retention. Your main heat loss would be from the dome base bricks (without insulation from the slab).

Unfortunately, I suspect raising the cooking floor that much will create access (and other) problems. I think most of us on the forum would advise you that the best option is to tear down your existing oven and rebuild it with the recommended insulation layer below the entire oven footprint...or you can just plan on short pizza parties that use a lot of wood...

Hope that helps you understand the problem(s) you are now facing.