Soapstone Hearth

[GianniFocaccia]

Now that my outdoor kitchen patio and walkways are almost finished I am very close to starting work on my actual oven! I came across a local ad for a guy selling a 36x36" soapstone slab for $90. It is 1 1/2" thick.

What is the practicality of placing this in the center of my 42" oven and surrounding it with the 2.5" firebrick that I'll be building the rest of the dome with? I understand normal fire placement is on the perimeter of an oven, and that I will have to build up an inch of oven floor under the soapstone.

The two questions I have are: Should I build the 1" soapstone 'base' out of fireclay/sand or 1" firebrick splits? Would a soapstone/firebrick oven floor heat evenly enough to be worth the added cost?

Thanks,

John

[lwalper]

Re: Soapstone Hearth

Soapstone is a great heatsink. I forget the math, but that sounds like a perfect hearth combination. Go for it!

[SCChris]

Re: Soapstone Hearth

The thickness of the stone is likley 3cm or 1.2 inches so you'll have a bit of work to get the level of the 2.25 inch thick firebrick and soapstone to match. You may find that the same place has a few leftovers to fill in the gaps. The other way to handle it would be to put the 1/2 thick bricks around the stone. I think they call these veneer bricks. I'll bet you can find the SStone leftovers. If I were going to put a SStone floor in my oven I think I'd consider putting in another inch of rigid insulation.



Chris

[dmun]

Re: Soapstone Hearth

Soapstone makes a great floor. Is it worth the cost? That's your call. Firebrick works fine.

Here's a link to a mha project: an oven with a soapstone floor.

[GianniFocaccia]

Re: Soapstone Hearth

Thanks Dmun. Excellent example of a 'partial' soapstone floor. A local stone yard says it has relatively inexpensive remnants that I think could be cut to fit inside my dome. They may not match but I'm not picky. Obviously, the fewer seams, the better.

Because soapstone reportedly heats up quickly, I'm thinking of laying it right on top of my firebrick floor instead of directly on my insulation (2" of Insblok on top of 3 1/2" of vermicrete). Would a 4" thick floor require a significant increase in wood to heat up?

[SCChris]

Re: Soapstone Hearth

I don't know what to tell you on the additional heatup time, it will take more time to heat more mass. I know that the SStone that I have is heavy. If I had to guess it would be that SStone is about twice the weight per volume relative to firebrick.

I don't know and can't guess how SStone cooks relative to brick. SStone is non-porous where brick is highly porous so cooking directly on these surfaces has got have some differences.

I'm very happy with the SStone entry surface it's easy to keep clean and to slide things in and out. The brick works great as well and in this inner oven area it is "self cleaning". I would also say that pushing things around within the oven isn't a problem with the brick but things would slide easier on the SStone.

Keep us posted on where you go with the SStone.


Chris

[GianniFocaccia]

Re: Soapstone Hearth

Thanks for the info, Chris. The soapstone looked attractive because of its smooth surface, much more accommodating than the rough (wirecut?) Pacific Clay firebricks I bought.

It will all come down to the cost I can get for the pieces.

[edsalldw]

Re: Soapstone Hearth

Hey Gianni,
Did you ever go ahead withthe soapstone/ Did it work well? Do you make bread with it?
I am about to build a 27" oven and can do the whole floor in one piece of soapstone. BU tsince it transfers heat 4 tiems as fast as brick Does it run the bottom of teh laoves. like brad buildrs says. But no one has yet said " I do it and it does burn - or does not burn."

Edsalldw

[GianniFocaccia]

Re: Soapstone Hearth

Ed,

Good questions, all. Yes, I did go ahead with the soapstone but haven't completed the oven yet so I can't comment on the effectiveness of cooking bread on it. Some random thoughts that might affect the construction of your oven with a SS floor:

1) try not to use a single piece of SS. If it ever needs to be replaced (it is very soft) a single piece would be impossible to remove. If you look at my thread OctoForno, you'll see what I did.
2) try to augment the amount of underfloor insulation if you go with soapstone on top of firebrick like I did. I have a total of 5 1/2" of vermicrete and ceramic board under the floor.
3) I have been told that once the floor has equalized down to the proper bread-making temperature it should work fine.

I am ecstatic that I was able to secure the soapstone in the dimensions I did at the relatively inexpensive price I paid: $200. I wanted to try a non-traditional floor and be able to report back on the relative merits of this kind of floor and whether it is worth it or not. The fact that east coast builders can reportedly get soapstone even cheaper makes me jealous. I feel a 27" pizza oven with a soapstone floor is a definite winner.

[lwood]

Re: Soapstone Hearth

Hi John,
I'm interested in how the soapstone performs. Soapstone has a higher thermal conductivity than firebrick but about the same heat capacity. Given that, it should give you a better oven pop than firebrick. Or lighter, fluffier crumb. Does it brown the bottom faster, don't know(that would not really be a good thing). Will be interested in your comments after you have used it a while. I am planning soapstone on my next oven.

[lwood]

Re: Soapstone Hearth

Hi John,
I'm interested in how the soapstone performs. Soapstone has a higher thermal conductivity than firebrick but about the same heat capacity. Given that, it should give you a better oven pop than firebrick. Or lighter, fluffier crumb. Does it brown the bottom faster, don't know(that would not really be a good thing). Will be interested in your comments after you have used it a while. I am planning soapstone on my next oven.

[david s]

Re: Soapstone Hearth

Soapstone is very soft. In fact it is the softest rock, it is easy to carve and sand. The resulting powder from the sandings is talc. Another name for soapstone is talcstone. Rub a little into your armpits. I don't know how it will go over time, but I would think it will wear away considerably, being so soft. Have heard of its use as a cooking surface in oven floors many times so it must be ok.

[GianniFocaccia]

Re: Soapstone Hearth

lwood,

I too am intrigued with soapstone's cooking properties and durability. My initial attraction to it was because my firebricks were unsuitable for a floor (neither square nor flat) and that I found a cabinetmaker willing to part with his cutoffs for $10/sq'. I also am the type to experiment, and the soapstone is one of several non-traditional (for home WFO's) elements going into my oven build.

Will it be suitable for bread? That is the number one question on my list: Does it's increased conductivity over traditional firebrick translate to faster bottom cooking than the dome can match? Jay (Texassourdough) says to let your oven equalize and come to the proper floor temp and you're good to go. Worst case scenario, if the bottoms are overcooked, next batch I use screens or some other diffusing material. I am open to testing and will certainly report my findings for all. Of course for pizza and flatbreads, it is considered optimal.

Will it hold up? The polished top scratched very easily during fitting and I'm afraid cast iron pots and oven tools may take their toll on it over time. Still, I am intrigued with how the floor will act as a heating element, both with a fire going and residual. I am a fan of casseroles (can you say lasagne?) as well as braised meats and pots of beans so I'm wondering if the soapstone will release it's heat faster/same as/slower than firebrick with the door on. Unfortunately, I won't have anything to compare it to, but I won't have anything to report until I get the damn oven finished!

There is a 2 1/2" firebrick subfloor underneath the soapstone, and I am equally curious to find out how fast the entire mass heat-loads during firing and the curve it gives up its heat. Again, with nothing to compare it to and no thermocouples, it is what it is, and all I can do is report what my IR thermometer reads both at the dome and the floor.

John

John