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Soapstone Technical Data – Calculated

It makes wonderful kitchen countertops. But putting aside its fabulous looks, soapstone (or soaprock) has many outstanding physical qualities. Especially those focused on coping with high heat levels. Some of the refractory properties soapstone has are even better than those found in heat resistant firebricks. How about well performing baking stones? Then stove or the once popular original fireplace linings.

Two colors of soapstone, dark green and light brown versions. A truly efficient baking oven system needs to meet well two certain thermal characteristics. The faster the heat absorption into the mass is the better (speed of heat soak from a heat source). Thermal Conductivity. That’s the first one. The second is Specific Heat. It’s about material heat storing capacity (how well and how much of heat is stored in the body mass – heat retention.) As it’s designed, soapstone fulfills both criteria and more extremely well – including a very high heat withstanding on reheating over and over again (unaffected like firebricks or better.)

Soapstone volume vs. weight Conversion Calculator

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• This automatic soapstone weight versus volume conversion calculator lets you instantly convert measurements of soapstone between mass kilograms g, ounces oz, pounds lb., kin, jīn, cubic volume in centimeters cm3, inches in3, feet ft3, yards yd3, meters m3, kin per cubic shaku (Japan shaku^3), jīn per cubic chǐ (China chǐ^3), Metric, US, Asian units from/to amounts into scale needed.
• The online tool is based on soapstone mass density 2.956g/cm3
• You may enter whole numbers, decimals or fractions ie: 5, 25, 29.33, 1/4, 17 3/8

Composition and properties of soapstone

By nature’s creation, in mass sense, this rock solid soapstone is composed of 67% of silica (Silicon dioxide – SiO2) and 33% magnesia (Magnesium oxide – MgO). Hence its wonderful thermal properties can be useful either in culinary arts practice or for room heating – ovens – stoves – pits – fireplaces. Or all such segments in one unit. It remains food-grade healthy in heated up or in cold state. Plus it will not degrade by heating nor peel down from reheating over and over again. In the other extreme of its resistance to stress from heat, soapstone copes real well also with freezing conditions. It is truly one amazing not just refractory material.

The high talc content, between 30% to 80% in its body, makes soapstone relatively soft. It definitely is not a hard rock like a granite for instance. When this soap stone gets heated reaching temperatures around 1100°C = 2012°F it hardens marginally (approximately twice as high level to what can be achieved in a semi-opened-source from wood fire heat.) But, at the same time, it does not shrink down in the heat as clay would. E.g. fireclay or pottery clays have a lots higher shrinkage ratio. Metal casting molds can be carved from this stone. It has very high degree of thermal stability. Hence another positive aspect related to business with refractories.

Thermal and mechanical data

Solid soapstone rock

Physical – Mechanical – Thermal – properties of soapstone
Specific heat capacity 785 J/Kg.°K
Thermal conductivity 12.5 W/m.°K
Melting point temperature > 2912°F = 1600°C (+)
Comprehensive strength 34 MPa (Megapascals)
Transverse strength 12.6 MPa (Megapascals
Permanent linear change
on Reheating to 1022°F = 550°C
nearly none (n/a)
Modulus of rupture 13.2 MPa (Mega-pascals)
Apparent porosity
(this is NOT a softness)
(or perhaps 99.9% non-porous)
Mass density of soapstone
2.956 g/cm3 grams per cubic centimeter
1.709 oz/in3 (cu in) ounces per cubic inch
2,956.0 kg/m3 kilograms per cubic meter
184.54 lb/ft3 (cu ft) pounds per cubic foot
4,982.5 lb/yd3 (cu yd) pounds per cubic yard
137.05 kin/cu-shaku Japanese kin per cubic shaku
218.3 jīn/cu-chǐ Chinese jīn per cubic chǐ
Naturally occurring properties variations should be expected.

Does soapstone wear off a lot?

Scratching it hard with a pointy-sharp hard metal object in guided motion will cause creation of a groove line (equally so with hard and dense firebrick which as a matter of fact also can be sanded with sandpaper as well.) However, I do not think a bread or pizza paddle is an issue though if the floor or hearth are looked after in a normal manner.

The answer will be hidden within this logical secondary question: Do benchtops, bath & kitchen soapstone counter-tops wear off? Nope … countertops do not wear off like shoes do! We use kitchen countertops made from soapstone in the morning, for making lunch and dinners and in between these hours. This explains it clearly doesn’t it?!

Wear characteristics of soapstone when it comes to usage;
in fireplaces & ovens’ hearths / floors. Down the road there are no problems with soapstone floors and hearths. Just the same as with countertops and various such surfaces. But those individuals who for their own reasons reckon they may use an oven heavily while at the same time perhaps somehow abuse it too much by placing e.g. heavy cast metal objects inside (the same thing then could apply to ceramic tile or firebrick surface), you can always make the floor segmented. The section which might need to be turned up side down or replacement, sometimes in the distant future, can simply be lifted, rotated or taken out and replaced with a new part of the same size. Which leads me to say once again …

… here is one very important aspect to consider! Related to heat expansion and in general long life for various materials exposed to high-heat levels. Soapstone is not excluded from this group. It’s about the temperature differences in material phenomenon. While temperature rises upwards and even more importantly on the other way backwards when the material is cooling down again. It expands and shrinks. It’s much better if fragments instead of thinner tiles or larger to large slabs are used. When a tile or a slab section in a floor heats up, these individual blocks get hot and they slightly expand, equally in theirs centers as well as around their edges (unless the heat source radiates onto a narrow area only, e.g. would be a burner flame.) But when things starts to cool down, edges or sides of some tiles might/always cool down in a faster rate than their centers. Meaning, they, the edges SHRINK down. This is such a common situation … which happens quite often. At this point the center of the slab or tile still keeps higher heat, there the body still remains EXPANDED. Ahh, bummer, a tile is expanded-larger in size in the center while at the same time it’s shrunk-smaller around its sides! Only a small difference is needed and that results in crack/s development/s in the cooled down areas. Potentially spreading across the whole tile surface. THEREFORE it’s better to use, right from the start, smaller segments of the size like bricks have for instance. With such smaller pieces everything breathes in and out again – nicely moves there and back again.

* The 392 degrees Fahrenheit or 200 degrees Celsius mark is when silica shrinks. It’s most often when material cracks. A slab or tiles can be protected from cracks happening – by slowing the cooling-down rate around this temperature level. Just by closing a door and proper outer thermal insulation. Insulate the large slab on which firebricks or soapstone pieces sit – then as it gradually cools down temperature in the whole slab will be even – it’s so simple.

Body of soapstone from certain sources can sometimes contain also alumina (Al2O3) and Calcium oxide (CaO), but these would form only a very minimal quantities. Too minor for consideration in regards to refractory properties.

Additionally on soapstone properties …

… and characteristics. Focusing on mostly from refractory matters perspective.

Due to the denser – heavier Magnesium oxide – MgO part, soapstone has density of 2.956g/cm3 (calculated 2.95556 grams per cubic centimeter.)
Soapstone has thermal conductivity 12.5 W/m.°K (property for heat conduction – temperature dependent heat sink into the stone as the material body. An opposite term would be a thermal resistance.)
Soapstone has the volumetric heat capacity of 785 J/Kg.°K (Specific heat – heat stored as energy – the higher the number the better capacity.)

Thermal conductivity (heat transfer within body)

  1. Silica – SiO2 thermal conductivity at r.t. is 1.38 W/m • °K = 0.9246 per 67%
  2. Magnesia – MgO thermal conductivity at r.t. is 35 W/m • °K = 11.55 per 33%
  3. Soapstone thermal conductivity calculated SiO 67% + MgO 33% = 12.4746 W/m • °K

Thermal conductivity at r.t. = room temperature level.

Specific heat (heat sink capacity)

  1. Silica – SiO2 specific heat at r.t. is 740 J/Kg • °K = 495.8 per 67%
  2. Magnesia – MgO specific heat at r.t. is 877 J/Kg • °K = 289.41 per 33%
  3. Soapstone specific heat calculated SiO2 67% + MgO 33% = 785.21 J/Kg • °K

Specific heat capacity at r.t. = room temperature level –
joules (J) kilogram (Kg [amount, body size]) per kelvin (K) unit.

Technical data

Density of soapstone: 2.956g/cm3

Thermal conductivity of soapstone at room temperature: 12.5 W/m • °K

Specific heat capacity of soapstone at room temperature: 785 J/Kg • °K

Magnesium oxide – MgO thermal conductivity is 35 W/m • °K

Magnesium oxide – MgO specific heat capacity is 877 J/Kg • °K

Magnesium oxide – MgO mass density is 3.58 g/cm³

Silicon dioxide – SiO2 thermal conductivity is 1.38 W/m • °K

Silicon dioxide – SiO2 specific heat capacity is 740 J/Kg • °K

Silicon dioxide – SiO2 mass density is 2.65 g/cm³

Soapstone vs. firebrick comparisons

Here we compare soapstone with refractory properties of firebricks which contain:

33% Aluminum
63% Silica
1.2% Ferric oxide
1.2% Titania
1.6% Accessory oxides

For comparison – 33% alumina + 63% Silica firebrick properties

Thermal Conductivity :

  1. Alumina – Al2O3 thermal conductivity at r.t. is 25.08 W/m • °K = 8.2764 per 33%
  2. Silica – SiO2 thermal conductivity at r.t. is 1.38 W/m • °K = 0.8694 per 63%
  3. 33% Alumina firebrick thermal conductivity – SiO2 63% + Al2O3 33% = 9.1458 W/m • °K

Specific Heat Capacity :

  1. Alumina – Al2O3 specific heat at r.t. is 880 J/Kg • °K = 290.4 per 33%
  2. Silica – SiO2 specific heat at r.t. is 740 J/Kg • °K = 466.2 per 63%
  3. 33% Alumina firebrick specific heat – SiO 67% + Al2O3 33% = 756.6 W/m • °K

These technical data numbers clearly explain why soapstone rock performs better (marginally perhaps) in heat-absorbing speed and also in heat retention.

Soapstone has higher thermal conductivity 12.5 W/m • °K than the 33% alumina content grade firebrick which is at 9.15 W/m • °K in comparison with the two materials. The soapstone has roughly three times (~3x) the bulk density 2.95g/cm3 … these firebrick types have 2g/cm3. Meaning soapstone has also heavier mass.

* Notice that, just like with Graphite, soaprock does not contain the Aluminum (Aluminum oxide – Al2O3) which clay based refractory products have a lot of in them.


The specific heat capacity of the soapstone comes to 785.2 J/Kg.°K where the firebrick is at a lower 757 J/Kg.°K heat storage. All is calculated @ room temperature level. Soapstone wins, it collects slightly more heat and gets hotter as well.

However, on the other side of the chamber – through the wall on the out-side opposite from the heat source, some suitable kind of thermal light-weight insulation has to be applied to prevent much of the heat energy loss. Otherwise the stored energy will run out into the opened air fast.

When it comes to culinary arts practice aspects (and suitability of soapstone for contact with food) – speed of the heat energy being transferred from the heat source through the hot face into the body mass, and also (obviously), how much of the heat energy is retained as in storage, are important considerations. After the bulk is saturated by the heat it performs, cooks or bakes for a long time, from the initial heating up. Soapstone isn’t toxic and it is material very suitable for contact with any foods.

There is only one small negative aspect I can think of. Soapstone does not have porosity. If a material is not porous it will not absorb moisture. A steam for instance. Such particular non-porous characteristic, that in itself is wonderfully positive for baking or for using such structure outdoors in freezing climates. Hence, on the other hand, when fresh pizza base is placed on a heated soapstone surface, and if it’s to be cooked rapidly – a method for producing the most delightful culinary results – the steam from under the fresh base isn’t absorbed by the rock because it behaves as something highly glossy (a glass would do the same.) Much steam gets generated in the early moments of placing the wet base onto the hot floor surface. Therefore there is the chance of not achieving that desired higher crisp. Although do not fret yet. Here are a couple of ways for how to overcome this problem. One is to simply uplift the base 1 to 3 times within the first 10 to 15 seconds. Second is to create the center surface out of several pieces, which creates those little gaps in between the segments for the steam to run out. Low heat and mid range firebricks do have the optimal porosity so no any issues. There is always a way for how to develop, improve, service, fix, repair any subjects needed!

When compared with firebricks, soapstone absorbs the heat faster and it also has bigger/better heat storage capacity. Soapstone gets a little more hotter too at the same time.

Convert a cubic volume of soapstone into a mass or weight number

in kilograms Kg, pounds Lbs, Japanese Kin, Chinese Jīn units.

soapstone equivalent measurements
cubic volume
– blocks –
– kgs –
– lbs –
– kin –
– jīn –
1 cm3 of soapstone 0.003 Kg 0.007 Lb 0.005 kin 0.006 jīn
1 in3 of soapstone 0.048 Kg 0.107 Lb 0.081 kin 0.097 jīn
1 ft3 of soapstone 83.7 Kg 184.5 Lb 139.5 kin 167.4 jīn
1 yd3 of soapstone 2,260 Kg 4,982.5 Lb 3,766.7 kin 4,520.1 jīn
1 m3 of soapstone 2,956.0 Kg 6,516.9 Lb 4,926.7 kin 5,912.0 jīn
1 cubic shaku (Japan)
of soapstone
82.23 Kg 181.3 Lb 137.1 kin 164.5 jīn
1 cubic chǐ (China)
of soapstone
109.2 Kg 240.6 Lb 181.9 kin 218.3 jīn

* shaku – Japanese foot, length unit = 303.0 mm – 11.93 inches – 0.9942 feet
  ( cubic volume block: 0.303m * 0.303m * 0.303m = 0.0278 m3 or 0.983 cu-ft )

* kin – Japanese unit of mass, 1 kin = 1.323 Lb or 0.6 Kg

* chǐ – Chinese foot, unit of length = 33.3 cm – 13.11 in – 1.0925 ft
  ( cubic volume block: 0.333m * 0.333m * 0.333m = 0.0369 m3 or 1.304 cu-ft )

* jīn – Chinese mass unit, 1 jīn = 0.596816 kilograms or 1.31575 pounds

Slabs from soapstone of a cubic volume

Block of soapstone of sizes Width 12″ x Length 24″ x Height 4.5″ (makes it 1296 in3 – cubic inches = 0.75 ft3 – cubic foot volume) weights exactly 138.4 lb – pounds = 2 214.44 oz – ounces. Or for any other measure in kilograms and grams of soapstone use the soapstone converter above for the conversion answers.

Soapstone slab of sizes Width 230mm x Depth 460mm” x Height 115mm (in volume 12,167.00 cubic centimeters = 0.012167 m3 – cubic meters) works out exactly 35.97 kg – kilograms in mass. For any other measure in ounces – pounds of soapstone or Asian including cubic volume units, easily calculate the outcome with the soapstone measures converter above.

References for Silicon dioxide and Magnesium oxide information:
1. Air Force Materials Laboratory (U.S.) “Thermophysical Properties of High Temperature Solid Materials”, Vol 4. (Google books)
2. Goodfellow Cambridge Ltd., “Metals, Alloys, Compounds, Ceramics, Polymers, Composites”

Respond to the Soapstone Technical Data – Calculated article:

47 Comments - post your thoughts

  1. Hi Rado,
    of course love your site – if anything too much info haha – I start reading and get sidetracked and then hungry. After about an hour reading I have to go eat, then sleep and then I’ve forgotten what I was doing before. Bali!

    The reason I’m writing to you is to find out if you have any Indonesian alternatives to refractory/fire brick. I’ve asked all the owners of pizza ovens here on Bali what they used and they have all just used normal bricks – which produce simple pizzas! I’ve heard a rumor that the Indonesian Soap Stone is as good as refractory bricks for distributing/keeping in the heat but can’t figure out what they mean by that either – there is so much stone available here and if you ask the seller “is that soap stone?” they look kinda vague until they think of the sales (although very nice people) and then they nod their heads vigorously and say “yes, yes, sop stone, very good”. Hmmmm?!

    Any help would be greatly appreciated.

    By Greg — Permalink

  2. Greg,
    When you cut soapstone and hold touch it on the side where it was cut, before polishing, it literally feels like holding a dry soap. You can use it of course. If you need post me a 0.5 to 1 kg piece I will let you know if it’s the right kind of material to use.

    By Rado — Permalink

  3. I love to cook and I’m a marble mason for over 25 years. My first oven is built out of soapstone brick and re-purposed eco friendly stone panels I make in Mendocino California plus other eco stone surfaces.

    By Marmo Man — Permalink

  4. I was interested in building an oven 11’x5′ for commercial use in making pizza. This oven is finished and has only 11000 lbs, using soapstone for its hearth.

    By Vittorio — Permalink

  5. I am thinking I could add some brackets inside and place a soapstone ceiling in the oven instead of the arch vault. I will try to get a few photos uploaded tonight.
    Mike in Atlanta, GA.

    By Mike — Permalink

  6. Hi Rado,

    just back from the East coast, had the Ferrari out there for the Ferrari Club of America Concours event. Won a gold level award for my car, a 250 GT/L Lusso. It is at the restoration shop now getting some of the little things corrected. Maybe I can stop by the oven on the way home and get some pictures of the Ferrari by the oven.

    Thanks for placing our short film on your home page, it immediately picked up on views.

    We have had many great pizza parties with the oven, your oven design works just like you said it would. We also have expanded our cooking now and usually do appetizers in a soapstone bowl or on the Tuscan grill before we get into the pizza party. The soapstone bowl works wonderful. We usually roll out a pie and then let everyone make their own. Lots of fun and I have gotten better so I can handle three pies at once in the oven so it goes much faster now.

    Hope to get into some bread making soon, anybody any suggestions on what type to start out with?

    added by admin:
    You are welcome Jim, likewise. Here goes again …

    Watch the oven film on the building details page and on home home page – Ferrari design/efficient oven project with the MTo refractory part inside (field-stones collected by hand, in nature around the house, for construction of these outer decorative walls.) What a character! Built by Jim

    By Jim — Permalink

  7. Hi Rado,
    I’m in the early planning stages of building a wood fired oven. Your site has been very informative!
    I wanted to know if you have ever used or know of anyone who has used soapstone rather then fire brick for an oven fire box? I have done a lot of web searching, and have not yet seen it done. I know soapstone retains and radiates heat far more efficiently than brick, but is there a reason it should not be used?

    By Audra — Permalink

  8. Hi Audra,
    Actually both firebricks and soapstone are great. The stone gets hotter though when compared with firebricks but this is something a cook or baker can easily get used to after knowing the oven. It can be also taken as an advantage in several aspects. But it’s not such a huge difference only marginally different temperature. In the site’s old vintage forum this was discussed a while back – plentifully – could you please look for the
    post, it should have soapstone mentioned in the title if I remember well. I used to work with soapstone back in Europe, in Australia I use only firebricks. No soapstone here to my knowledge.

    By Rado — Permalink

  9. I know it’s the festive season (Merry Christmas) by the way and everybody is in holiday mode. I have a copy of your cd which has being extremely helpful for fixing (improving) my previously built oven and stove. my oven is the igloo type design. If possible I have a few questions to ask. (1) under the hearth there is no vermiculite which may explain the rapid heat loss from the base. could sand be used under the cement board as an insulator or soapstone on top firebrick floor? (2) Instead of concrete cladding I have used another layer of old red clay bricks touching firebrick chamber which through heat expansion has caused slight movement in mortar joints. Would I be able to leave this brick wall, then insulate with vermiculite as I have done on top of chamber and then either brick up outer wall or render?

    By Anna — Permalink

  10. Hello Anna,
    Thanks for your nice words.

    1. Put some thermal insulation under the slab, something which is light in weight, like insulating blankets or vermiculite. You will need to hold it under the slab by some board and prop or hold it up somehow. Not difficult to do. Even though the heat soaks downwards in slow rate, a dense material like the sand wouldn’t prevent the heat from being conducted through it and plus released out. If you put soapstone on top of bricks in the floor you will effectively add heat absorbing mass to the hearth. Where did you buy soapstone in Australia? From your email address I can see you are in .au

    2. Yes. Cover the heavy bricks with a good layer of thermal insulation, again lightweight material. Then you can box the oven in if the space around permits.

    By Rado — Permalink

  11. I look forward to getting your building plans disk so I can start my oven as soon as the frost is out of the ground. Your site has been helpful and is well done. What do you think about using a 1.5 in. Thick soapstone slab for the floor of the oven. I can only get fire brick with a 27-30% alumina content, I thought the soapstone may have better moisture absorptive properties and I like the idea of it being an organic material. Thanks for your attention.

    New London, NH USA

    By Paul — Permalink

  12. Hey Paul,
    Thank you for your generous support! Please reread this page, I added into the text everything what you need. Let us know how you go with the 1.5 inch soapstone! The 27-30% alumina content bricks aren’t bad either.

    By Rado — Permalink

  13. It is a wonderful website…
    Now the big question for me.. I recently built a wood fired oven in my house in the kitchen.. The problem I have is that I lined it with 2 inch soap stone piece with metal angles behind it on the sides.
    One large piece soap stone was used for the bottom.. I lit the oven and baked some bread which seemed to go very well.
    However when the oven cooled, I went to clean out what remained of the ashes and found that the bottom stone was cracked badly and could not be used again..
    I can’t figure out what should I use for the bottom stone where the fire is built > I need to have something that not only absorbs heat but will take the intense heat of the fire when it is fired up..

    Can you please give me some advise and help.. I have tried, soap stone, fire brick. Both did not work out.. What shall I use?

    Richard L
    Norwich, New York

    You can’t imagine how much I would appreciate the help…

    By Richard — Permalink

  14. Hi Richard,
    I am just little-bit confused from how you wrote it. for what you need both, the firebricks or the soapstone material, should be working in this set up perfectly. If done properly. Could you please email us images of the floor? I need to see how you structured it. Is the soapstone pieces, surface sitting on those metal pieces in sides? Is there a gap space under the stone slab? Please read whole this article, it can provide you with a few structurally oriented answers.

    By Rado — Permalink

  15. Rado,

    Happy Birthday.

    I found your site after seeing a tv show on making a wood fired pizza oven. It’s nice to see someone with such passion for both building these ovens but knowledge as well. And most important to me is your willingness to share your successes and best practices with all who wish to read.

    I am ready to build my oven. I have a good bit of experiance with block, mortar, and stone as well but I am very interested in seeing your tutorial along with any suggestions on my oven. I would like to have an oven large enough to cook pizzas for 10-15 people along with the ability to cook steaks, roast, maybe even throw in a rotissery. If possible I’d like to have one oven but I can certainly add another for the second cooking feature. My space is outside in a nice shaded oak tree area in my back yard. The space I have to work with is approximately 20’x20′ so I have plenty of room. I’m in the stone veneer business, and also have access to about 40-50 pcs of 3cm 25.5″x48″ green soapstone from Brazil. I have heard and read that these can be used in the oven but some posts state that it gets too hot or holds too much heat which burns the pizzas. Your advice is greatly appreciated. If I can use these for the countertops alone I will be happy but if I could somehow incorporate it in the oven that would be very nice. I am ready to order your DVD and should be ready to build within 3-4 weeks.

    Thank you again for your expert advice; from the looks of everyone who has posted a comment you have quite the following! I searched everywhere in my state and so far I haven’t found anyone who really knows anything about building these ovens (or at least they haven’t wanted to tell me).

    Thanks again and I hope to hear back from you soon.

    Tampa, FL.

    By William — Permalink

  16. William,
    Thank you very much for your nice words about our work. Ahhh, those 40 to 50 soapstone pieces sound excellent, I would love to have them too. Lucky you. I have just send you email. Also with the details on the DVD.

    By Rado — Permalink

  17. @ Rado – thank you for all your hard work, much appreciated. Will be ordering your plans myself.

    @ William – In my mini size WF Oven at around 550 degrees my pizza pies take close to 5 minutes to be fully cooked. I’m cooking on a 1.25 inch thick soap stone pieces layered on top of firebricks with minimal amount of fireclay in between these two materials not to break the heat transiting all the way through the hearth. To burn pizzas, or other doughs, etceteros, the soapstone would probably needed to be located right above fire flames somehow and then heated too much from under there. Just my two cents because I also create a higher temperature in this oven, say 800+ degrees for making Neapolitan style, then it takes 2 minutes and less to cook! Even then pizzas don’t burn on this stone.

    By Joseph — Permalink

  18. I have a question as to hearth materials. I have access to some high quality very thick (5-8″) slabs of hard soapstone. I am wondering how this material would do as a hearth instead of firebrick. I can use either one, whichever is better. The oven will be used at a customers home for pizza and other baking needs. It seems to me that it might work, due to the fast heat absorbtion and slow release of the soapstone. I have seen masons using soapstone for hearths in commercial pizza ovens, yet you use firebrick, I am wondering which is better/why? Also, could a layer of soapstone be added over the firebrick dome to increase the thermal mass/cook time? Thanks for the website and I look forward to receiving my CD’s. Matt S

    By MattPermalink

  19. Hi Matt,
    Yes soapstone is used often, usually for pizza though as it gets hotter. It conducts heat same way. There is nothing wrong with firebricks too. I used soapstone in Europe, I can’t get it here. You can add pieces over the firebricks if you would like to increase heat absorbing mass. Soapstone can be sanded into smooth surface too, same for firebricks but are a bit harder. Search for ‘Peter Moore Masonry’ website they use this material too. Rado

    By Rado — Permalink

  20. Thanks Rado,
    I have seen Peter Moore’s website in my research. I really
    appreciate the answer.

    By MattPermalink

  21. Dear Rado,

    I laid the firebricks yesterday, but they don’t look as good as yours.
    The cracks look a lot bigger than yours, and that must not be good for the bottom of the oven.
    I was wondering if I used the wrong type of brick, I didn’t lay them correctly, or both.

    Do you think that adding a 1″ thick layer of Refractory cement over the top of the bricks would be a bad idea?
    I just think that a smooth surface on the bottom of the oven is kind of important.

    What do you think?

    What about a 1.5″ layer of soapstone over the firebrick?
    Any other ideas for a smooth floor?

    The bricks are heavy like a regular brick. They just don’t look perfect like your bricks.
    Brickyards around here only carry 2 types of refractory firebricks, these are the better ones.
    I’m not supposed to get them from a refractory supply or something, right?
    They also aren’t white like yours, they are more peach colored.
    I can buy soapstone as well. But soapstone vs. firebricks basically are nearly equal to each other when it comes to using each in heat applications.

    Brian from Malibu, CA

    By Brian — Permalink

  22. Brian,
    Slow down Mate, all is fine don’t fret. Are you a perfectionist or sometning?!

    By looking at your photos, from the angle I could see you laid them in a nice and tight way. The gaps appear to be only in upper part closer to the surface and are very little it’s all nicely in-line. I couldn’t even see gaps in first photos. This is only cosmetic but not too visible anyway, the gaps will get filled packed with ash when the oven is used. Then the floor becomes smooth like I am ;)

    1″ concrete or soapstone is too thin don’t even think about it. In heated and then backwards cooled down floor the thin tiles and such concrete layer would crack over time. Plus for larger to large surfaces clay firebricks are much better then heat resistant concrete! I would leave it as is right now if I built the oven for myself ( you have it very close, you could do it professionally.)

    By Rado — Permalink

  23. To all those DIY people who worried about soapstone getting too hot for mastering dough. It is not so. Soapstone has been used for the same purpose for hundreds of years always with excellent results. You can find soapstone in old kitchens on ships. Only several modern day id**ts who try hard to sell low quality prefab igloos or kits and other cheap artificial stone benchtops or alike worthless products desperately spreading misleading info to suit their current needs.

    By Peter — Permalink

  24. […] mortar if any, mostly lime was used those days. Interested in firebricks physical properties or soapstone (soaprock) technical […]

    Pingback Alternative for Fire Bricks are the old red clay solid bricks. Firebrick substitutePermalink

  25. […] thermal conductivity and alternative for firebricks replacement, or on the also excellent soapstone – soaprock technical […]

    Pingback Firebricks are actually fire clay bricks. Thermal conductivity. Cutting with diamond wheel.Permalink

  26. Total information on the whole about thermal conduction coefficient of soapstone material behavior, related to soapstone products usage.

    By David — Permalink

  27. I have several 1 1/4″ soapstone pieces with heat resistance to 2000 degrees and it is great to find out, or to learn, that soapstone is also a thermal heat conductor. My soapstone off-cuts come from a maker of kitchen bench-tops. Because of its thermal properties I intend to make stove with oven on one side heated up via a firing box located under these two and channel the heat in. Hot face lining of these three will be made from the soapstone.


    By Is soapstone a thermal heat conductor? — Permalink

  28. I have been cooking on heated soapstone surface for 3 decades. The same and only one flat piece of soapstone.

    Seems that soapstone’s thermal properties or qualities are very appropriate for creating not only fire places and stoves but equally for pizza ovens and bread baking ovens. Scott

    By The soapstone thermal properties — Permalink

  29. Thank you. I wanted to know what is the heat capacity of soapstone. What is the specific heat of soapstone numbers for cooling by freezing it and heating by applying heat to this stone.

    By Soapstone heat capacity — Permalink

  30. Soapstone has special mineral properties that are very ideal also for fireplace linings as the rock resists the continuous high heat. Much better than concrete and it lasts forever. Does anyone know of a place which sells soap stone fire linings in UK?

    Soapstone’s thermal insulation characteristics aspect is out of question because the material conducts and absorbs heat extremely well, not just relatively well. But it has OK electrical insulating properties.

    What is better refractory for heat sink, cement or soapstone?

    What is the bulk density of fireclay joined soapstone g/cm as per volume mass density?

    What would a (one) soapstone slab 24 inches wide by 24 inches long by 5/8 inch thick (thin tile) weigh in pounds. Which equals to 360 cu-in in bulk volume per the soapstone slab size.

    24″ * 24″ * 0.625″ = 360 cubic inches (0.2083 ft3 / cubic foot) in tile volume …

    360 cubic inches of soapstone = 38.45 lb of soapstone

    By Fire linings UK — Permalink

  31. can I take dry powdered clay , put in a mold , apply tons of pressure and fire it . what will be % of shirkage

    By steve — Permalink

  32. Steve,
    I see where you coming from, pressing a semi dry stuff to pack moulding it. The only difference in shrinkage will be in the green drying, within the time till it gets completely dry when it can go into a kiln. A lot less shrinkage rate there if basically the water isn’t present. Bur from this green state (dry and cold), the shrinkage in the kiln will be pretty much the same. But I would be interested to see it, all I said, however, the press could marginally make some slight difference.

    This is page about soapstone, maybe you looked at both pages.

    By Rado — Permalink

  33. I am building a rumford style fireplace with an arched opening. I am using soapstone bricks for the fire back and a slab of soapstone for the hearth measuring 40 inches wide extending 40 inches out by one and a half inches thick. The arch is also to be soapstone with 10 segments measuring 4 inches across the bottom tapering up to 6 inches across the top and 7 inches high by 5 inches wide. The soapstone key stone is to be 4 inches across the bottom by 8 inches across the top and 12 inches high by 6 inches wide. The stone I will use has a mohs scale of 5 with veining. Will I have a problem with expansion in the hearth and arch and what advantages or disadvantages will I have with this arrangement?

    By Peter — Permalink

  34. After reading this information I’m even more into a soapstone material for doing up my kitchen. I’m off to learn more about its use in Australia.

    By Maureen | Orgasmic ChefPermalink

  35. Why hasn’t or has anyone made soapstone as some paneling? Have they? Why can’t they. Sure could use some large flat-cut soapstone slabs and pieces.

    By Mrs. Marann Caudill — Permalink

  36. Alternatively, can soapstone be frozen e.g. countertops similar to Coldstone’s?

    By Nelore Lanza — Permalink

  37. Hi wow what a great site!
    I am embarking on making a wood stove, metalworker, and I would like to cast and hang cast panels on the stove to hold the heat overnight, alternative to soapstone, I don’t think I want insulating castings but something that will emulate soapstone and soak up the heat and give it back throughout the night, something like firebrick material, ceramic concrete?
    Any ideas, products? Mixing instruction?

    By andy — Permalink

  38. I have a Osburn 2400 wood stove with a steel top. Can I install a custom fabricated soapstone top on the steel top. I would have a hole cut for the 6 inch flue pipe. 30″x 22.5″ also 1 3/4″ thick.

    By John — Permalink

  39. Hey Rado, love your site!
    I’ve been building soapstone fireplaces for 20 plus years, Tulikivi mainly, and mostly with black ovens. I’ve only built 8 free standing ovens, barrel type and bee hive. The use of soapstone, especially in the floor, is the best choice for thermal conduction and durability. I’m presently building a bee hive (Igloo) 36″ diameter with a 60 mm thick soapstone floor. I’ll send pictures once it’s completed.

    By Glenn Luse — Permalink

  40. G’day Glenn!
    60mm soapstone floor is fantastic. You are correct about the soapstone choice and its qualities, and yes especially for the surface. Cannot wait to see the images from your project in fact. Do you buy soapstone already pre-cut or do you size own to various measurements needed?

    By Rado — Permalink

  41. I have stock of different soapstone sizes left over due to changes in orders and such. I layout a pattern usually to fit what I have available and cut what is needed in tighter situations.
    Finnish soapstone is imported often by container to a Tulikivi soapstone fireplaces dealer in West Virginia. I order material through them. They also have soapstone firebricks which are quite expensive. ($6.00/pcs) Firebrick are $1.40 here in PA.

    By glenn luse — Permalink

  42. Quite a difference in price between firebrick at 1.40 per brick and the brick cut from soapstone which is 6.00 each! For the floor only the price would still be manageable, although if the floor surface could be put together out of unique pieces of different sizes or soapstone, nicely fitted together, then by all means it gets much better.

    By Rado — Permalink

  43. Hi what a great site and thank you for putting in the time to answer questions. I want to use a piece of soapstone to heat up to 400 degrees which I will then place inside of an insulted container to use as a portable oven when closed. The diameter needs to be 8 1/2 inches but I was hoping you could tell me how thick you believe it needs to be if used to heat a space that’s about the size of a 5 gallon bucket. I also read some issues about cracking and was hoping you could let me know what I can do to prevent cracking of soapstone when used in this manner.

    By Bryce — Permalink

  44. Sir,

    I have a Soapstone Quarry in India it’s Chemical contests are as below. Please inform is this Soapstone is good for Wood Stoves/Ovens?

    Sio2 53.2%
    Al 203 18.4%
    Fe 203 8.74%
    Tio2 0.41%
    CaO 1.26%
    Mgo 13.3%
    LOI 4.62%

    By Krishnamurthy — Permalink

  45. From looking at its data it seems to be a good soapstone.

    Try this for an additional test of the soapstone:
    cut a piece of soapstone precisely 30cm long. Or make/scratch 2 permanent marks on it in the accurate 300mm separation. It can be cylindrical or a cuboid rectangular prism object say with 5cm x 5cm x 30cm (or in inches 2″ x 2″ x 12″) dimensions. Heat the piece well prolongedly in fire. Cool it down slowly, gradual cooling down can be achieved if the soapstone is covered by the red hot embers until it all reaches temperature when it can be touched by hand. Measure the distance again if it’s still the same or whether the soapstone shrunk to an extent. Observe it for other possible changes.

    By Rado — Permalink

  46. Hi Fellow!

    ” 3. Soapstone thermal conductivity calculated SiO 67% + MgO 33% = 12.4746 W/m • °K
    3. Soapstone specific heat calculated SiO2 67% + MgO 33% = 785.21 J/Kg • °K ”

    I’m surprised how direct way You calculate the thermal conductivity and specific heat from basic values of Si02 and MgO, only by adding least You should take the percentage parts in to account .. but it doesn’t go so simply .. in fact it can’t be calculated, it must be measured in practice. The correct calculation could perhaps be done through thermodynamic modeling … but measuring is the best way !!

    Many times these kind of materials can have physical properties with smaller values that the original base materials. Most common example is metals: Mixing metals You get compound which melting temperature is less than melting temperature of original metals!

    With Best regards ilkka

    By Ilkka Korhonen — Permalink

  47. G’day Ilkka Fellow!

    Thanks for great points. Please note that on this page the approach to calculate the thermal conductivity is to procure an approximate thermal conductivity in an easy quick way. It is however a good way IF/considering the derived number isn’t required for some precise laboratory purpose or something in line of higher precision. Also, it is a motion for non-metallic materials for example refractory fireclay based or minerals, all sorts of rocks not only the soapstone material.

    Since I read your input I have been thinking about the metals too. You mentioned the lower melting temperature point. I am pretty sure we had this in school but need to look it up now. Specifically about the lower values when heating mixed metals. How would you measure, or describe in theory, the melting temperature of say 3 mixed metals (a hypothetical alloy) with such a different melting properties the lead, iron, copper, are having for instance.

    With compliments Mate.

    By Rado — Permalink

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