What is Soapstone? 

A metamorphic rock, primarily made of the mineral talc. It is not anything like limestone, marble, granite, slate or sandstone, it’s a totally different rock.  It’s also not the rock “Talc” which is translucent and used primarily for carving. Real Soapstone is technically called “Steatite”.  It is reasonably soft and can be scratched with metal.

The countertop market has a number of products that are called “soapstone” but in fact are different kinds of stones, such as slates, schists, serpentines, volcanic tuffs, etc.    In particular, what is sold as “Black Soapstone” or “Dark Soapstone” is usually NOT soapstone.  These stones will not have the same thermal properties as true steatite soapstone and could crack or spall in a fireplace application.

Our Soapstone is quarried in Brazil.  Stonetrade has been importing Brazilian Soapstone to the US for almost 30 years.

Can I get Soapstone in a different color ?

All varieties of true steatite soapstone are gray.  The stone varies somewhat in the amount of patterning and white veining, but overall it is a very consistently colored stone.  If you want the soapstone to be darker, you could apply a mineral oil/wax formulation, or a color enhancing stone sealer.  However, these products are not rated for use in high heat applications, and so should only be considered for decorative fireplaces that will not be actually used.

What’s so special about Soapstone and heat?

All stones expand when exposed to heat and shrink when they cool.   The amount that they move is called their “thermal coefficient of expansion” and it varies alot from stone to stone.  The more a stone expands and contracts, the more likely it is to crack or spall.

The mineral talc has a very low thermal coefficient of expansion.  So when it is heated and cooled, soapstone stays relatively static, and it is therefore much less likely to crack and spall than other natural stones like granite.   

Some people thing Basalt or lava rock, being so recently molten, should be good with heat, but the opposite is true: because of its crystalline structure, Basalt cracks and spalls very easily. 

Plus, soapstone is extremely dense, and its molecular structure permits it to absorb and retain heat for long periods of time.   The ability to store heat can be used to increase the efficiency of a fireplace or stove.

Soapstone is of course non-flammable with a super high melting point, and talc is not chemically reactive to the caustic gasses emitted by burning wood, so it won’t stain or discolor in the same way as marble or limestone.  Soapstone is also non-porous so it won’t trap soot.  

How long has Soapstone being used for heating applications?

Soapstone stoves have been used in Russia and Scandinavia for centuries, and many cultures worldwide, including Native Americans, have traditions of carving cooking vessels out of solid soapstone.  Again, this takes advantage of soapstone’s ability to absorb and retain heat without cracking.  In Scandinavia in particular there is a modern industry of massive masonry heaters which are clad with soapstone.   Just one of these can heat a whole house from a single firebox, but they typically weigh a ton or more and are probably too large and elaborate for most American and Canadian houses.

An alternative is a more typical US style cast iron framed wood stove lined or coated with soapstone tiles.  Stonetrade has been selling soapstone to North American wood-stove manufacturers for almost three decades.  The soapstone tiles are slotted into the cast iron frame of the stove and provide more thermal mass. Soapstone stoves are proven to stay hotter for significantly longer than models made only from cast iron.

Soapstone firebrick can also be used as a lining for ovens, increasing their efficiency.  We’ve had several customers use them to make pizza ovens, and we sell (in volume) soapstone pizza stones that will keep the pie hot long after it is brought to the table.

What are the advantages of Soapstone firebrick over regular firebrick?

One of the best ways to get the benefit of soapstone is to use it to line the inside of a masonry fireplace, instead of regular firebrick.  The benefits are both technical and aesthetic.

Regular (typically yellow, beige or red) firebrick is a ceramic product, pressed and fired.   It is intended only to insulate and protect the masonry structure behind it.  It has virtually no heat storage capacity and is brittle and friable.  It’s quite porous and will trap soot on its exposed surfaces.  It is available in a limited range of colors and finishes, and can have a raw, unfinished look.

Soapstone firebrick is sawn from large blocks of natural stone and is extremely dense.  While it too will protect the masonry behind it from the flames, it also functions as a heat storage system, saving calories that otherwise would go straight up the chimney, and radiating that heat back into the room.  

Honed soapstone bricks show natural veining and texture, and give a crisp, finished and refined look to the lining of a fireplace.  If you’ve made the effort to make the surround and mantel look great, why not make the firebox look great as well?   After all, you actually spend the most time looking at the firebox!

In particular Soapstone firebrick is becoming a popular material to line the inside of IsokernTM or FireRockTM Fireplaces. 

Will Soapstone Firebrick meet code to be used in a fireplace?

Yes, we have tested our soapstone and it meets ASTM C-1261 (Standard Specification for Firebox Brick for Residential Fireplaces).   If your fire inspector requires it, we can provide a copy of the test results.

This document is the intellectual property of STONETRADE® and may not be reproduced or reprinted, whole or in part, without the express written consent of STONETRADE®.  WWW.STONETRADE.COM