my slabe is worm !!!

[Ammora]

hi there
the temperature of my slabe is about 60C? (MEASURED FROM UNDERNEATH)after about 7 hours.
IS THERE A PROBLEM ???

[andreas]

Re: my slabe is worm !!!

hi there ammora is that your slab under your oven floor ?? did you insulate your floor other than the bricks and did you put an insulating bed inside the slab when you poured ?? 60 deg under after 7 hours how hot did you get inside the oven ??

[RTflorida]

Re: my slabe is worm !!!

60C is 140F, right? seems a little high. The warmest I have seem after a 6-7 hr burn is about 50C, 125F. My hearth insulation consists of 4" of vermicrete.

Did you have a big fire going the entire 7 hrs? how much/what type of insulation?

RT

[david s]

Re: my slabe is worm !!!

If your oven is new it will still have a fair amount of moisture in it which will result in heat conducting through the damp materials. Keep firing it and the performance will improve.

[Ammora]

Re: my slabe is worm !!!

If your oven is new it will still have a fair amount of moisture in it which will result in heat conducting through the damp materials. Keep firing it and the performance will improve.

thanks a lot for the response. thats what i want to hear, it is the moisture!
i only insulate with clay 4" (no vermiculite its not available in my country-Egypt) and for the second burn for 1 hour it reaches 300C inside the oven 7 hours later
it reaches 60C but it is OK i can live with that i was only worried about not weaken my slap due to the repetitive worming.

[Ammora]

Re: my slabe is worm !!!

hi there ammora is that your slab under your oven floor ?? did you insulate your floor other than the bricks and did you put an insulating bed inside the slab when you poured ?? 60 deg under after 7 hours how hot did you get inside the oven ??

i only used clay 4" as insulator between the slap and the hearth, no bricks i used marble works good for me -so far-

60C is 140F, right? seems a little high. The warmest I have seem after a 6-7 hr burn is about 50C, 125F. My hearth insulation consists of 4" of vermicrete.

Did you have a big fire going the entire 7 hrs? how much/what type of insulation?

C

RT

Yes i have a big fire but not for the entire 7 hrs 1:30 big fire then i left the embers for the remaining time and the oven gets to 300

[nissanneill]

Re: my slabe is worm !!!

Ammora
I think that you are going to experience some serious problems with your build. To start with, clay is used as a heat sink, ie. thermal mass and not as an insulator! You need something that is going to stop the heat from draining out of your oven and in this case your floor.
My other concern is you use of marble. I would be hesitant in using such materials a s it is likely to break up with high heat, spalling and small sometimes sharp pieces explode off the surface. Just watch out, especially if you drop some cold ingredients or water when you spray for steam when bread baking that the cold water doesn't cause the problem!
Let's see if anyone else has similar feelings and opinions, as I hate being the provider of bad news!

Neill

[dmun]

Re: my slabe is worm !!!

The one time I was in Egypt, it didn't exactly look forested. I would suspect that firewood is expensive there, and I would think that proper refractory insulation, above and below your oven, would be money well spent.

It bears repeating: Sand is not an insulator. Gravel is not an insulator. Broken glass is not an insulator. And, No, clay isn't an insulator either.

[Neil2]

Re: my slabe is worm !!!

Your slab is OK to about 500 F.

[Archena]

Re: my slabe is worm !!!

Wood ash is an insulator - and a byproduct you're gonna have anyway.

[Ammora]

Re: my slabe is worm !!!

Your slab is OK to about 500 F.

thanks a lot that was my concern

[Ammora]

Re: my slabe is worm !!!

Ammora
I think that you are going to experience some serious problems with your build. To start with, clay is used as a heat sink, ie. thermal mass and not as an insulator! You need something that is going to stop the heat from draining out of your oven and in this case your floor.
My other concern is you use of marble. I would be hesitant in using such materials a s it is likely to break up with high heat, spalling and small sometimes sharp pieces explode off the surface. Just watch out, especially if you drop some cold ingredients or water when you spray for steam when bread baking that the cold water doesn't cause the problem!
Let's see if anyone else has similar feelings and opinions, as I hate being the provider of bad news!

Neill

so far the marble is doing great (it is a black one by the way)
and for the clay YES U R right
but i forgot to mention that under this 4" of clay lays a layer of punctured red
brick (as in the attached photo) the holes (air) in the bricks serves as the insulator
sorry every body for missing to say so

[Ammora]

Re: my slabe is worm !!!

The one time I was in Egypt, it didn't exactly look forested. I would suspect that firewood is expensive there, and I would think that proper refractory insulation, above and below your oven, would be money well spent.

It bears repeating: Sand is not an insulator. Gravel is not an insulator. Broken glass is not an insulator. And, No, clay isn't an insulator either.

I agree Egypt is not forested but the fire wood is available and it is not expensive (some times i get it for free!!)
and U R right about the insulation stuff