Soapstone vs Firebrick ??

[lwood]

Re: Soapstone vs Firebrick ??

Great bit of research on soapstone vs firebrick. I don't think you have to worry about stains on the inside of your oven. At the temps we are working the oven is self cleaning fire brick or soapstone. I think the smooth texture of the soapstone would be a nice working surface inside the oven. The thermal properties all seem to work in the soapstone's favor except the added insulation required (good observation). That is a big difference in thermal conductivity.....6X. That should really add to your oven spring. Watch out for charring on the bottom. You can always hold the pizza closer to the dome to finish it off.

[SCChris]

Re: Soapstone vs Firebrick ??

Scott,
I think you'll find that the brush isn't a problem with your Soapstone. As it's been presented to me, the darker more homogeneous stone is what you want in high temp environments, like ovens. Soapstone is not a single mineral but a mixture of minerals and it varies greatly in hardness because of the Serpentine and Talc that are the greatest components of Soapstone. The reason you want the darker more homogeneous stone is because although the lighter component of Soapstone, the Talc, can handle the heat, the expansion difference between the Serpentine and the Talc will ultimately crack the softer Talc, and because of the hardness difference of the darker Serpentine I don't think you'll find that the brass brush is any problem at all. I also think one of the reasons we use wire brushes is the because of the texture and absorbency of the firebrick. Soapstone is much less prone to holding onto spills, ambers and ash.

I think that the heat conductivity of Soapstone makes some design changes to the typical WFO beneficial. My opinion is that the sub-floor insulation should be beefed up and that some sort of thermal break should also be designed in at the entry door area.

Additionally, the amount of thermal capacity, heat storage, that the Soapstone offers is of course related to the thickness of the stone installed. Soapstone is available in firebrick dimensions and in larger slabs but most commonly it’s available in 2 and 3cm thicknesses. These most common sizes provide approximately ? the amount of thermal storage of firebrick. My question is, if the 3cm material is installed rather than firebrick, how important is this heat storage difference? I haven’t mulled this through completely at this point.

I have to say that firebrick isn’t the ideal material for the entry area because of the inevitable staining that happens here. Stone is a much better match for the entry in my opinion. Granite or Soapstone or some other nonporous material seems to make better sense in the entry area.

Chris

[scott123]

Re: Soapstone vs Firebrick ??

One other huge difference when comparing the two is durability. Soapstone is very soft and scratches easily. This pretty much rules out metal utensils. I'm not even certain soapstone could handle a typical brass brush.

Soapstone's superior conductivity and thermal indestructibility make it the Rolls Royce of home oven pizza stones (using wooden peels), but, for the potentially more abrasive environment of a WFO, at this point, there's a few logistical kinks to work out.

I'm presently building a WF soapstone oven, so I'm in the process of working these kinks out as we speak.

[SCChris]

Re: Soapstone vs Firebrick ??

Other common materials:

Thermal Capacity

Iron 0.450
Aluminum 0.890
Water 4.181
Concrete 0.880


Thermal Conductivity - k - (W/mK

Calcium Silicate insulating Board at 600F 0.097
Iron 60
Aluminum 250
Water 0.58
Concrete 0.42 to 1.7
Gold 310
Silver 429


Chris

[SCChris]

It looks like the Soapstone and Firebrick weight is almost identical per volume. The thermal properties of Soapstone and Firebrick differ in two ways. First the Thermal Capacity of brick, not specifically firebrick, is about 85% of Soapstone. Secondly; Brick transfers heat slower than Soapstone, seemingly at 1/6 the speed. This higher transfer rate can be thought of like the R-Value rating of insulation. My guess is that what this means for the WFO and Pizza Stones is that the Soapstone will heat faster, cook pizza faster, even out temperatures within the oven faster and cool faster. I would guess that an oven with a Soapstone floor would benefit from more sub-floor insulation than a typical Firebrick floor oven.

Thermal Capacity

Brick 0.840 Cp J/(gK)
Soapstone 0.98

This information was found at; Wikipedia "Specific heat capacity of building materials" and Tulikivi.com "The characteristics of soapstone"

Thermal Conductivity

Brick between 0.98 and 1.13 W/m.K
SStone 6.4 W/mK
This information was found at; Traditionaloven.com "Firebricks – heavy dense fire clay bricks" and Tulikivi.com "The characteristics of soapstone"

Material in kg/cu.m

Brick, fire clay 2403
Soapstone talc 2400

Chris