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A Low Cost Tester of Glaze Melt Fluidity
A One-speed Lab or Studio Slurry Mixer
A Textbook Cone 6 Matte Glaze With Problems
Adjusting Glaze Expansion by Calculation to Solve Shivering
Alberta Slip, 20 Years of Substitution for Albany Slip
An Overview of Ceramic Stains
Are You in Control of Your Production Process?
Are Your Glazes Food Safe or are They Leachable?
Attack on Glass: Corrosion Attack Mechanisms
Ball Milling Glazes, Bodies, Engobes
Binders for Ceramic Bodies
Bringing Out the Big Guns in Craze Control: MgO (G1215U)
Ceramic Glazes Today
Ceramic Material Nomenclature
Ceramic Tile Clay Body Formulation
Changing Our View of Glazes
Chemistry vs. Matrix Blending to Create Glazes from Native Materials
Concentrate on One Good Glaze
Cone 6 Floating Blue Glaze Recipe
Copper Red Glazes
Crazing and Bacteria: Is There a Hazard?
Crazing in Stoneware Glazes: Treating the Causes, Not the Symptoms
Creating a Non-Glaze Ceramic Slip or Engobe
Creating Your Own Budget Glaze
Crystal Glazes: Understanding the Process and Materials
Deflocculants: A Detailed Overview
Demonstrating Glaze Fit Issues to Students
Diagnosing a Casting Problem at a Sanitaryware Plant
Drying Ceramics Without Cracks
Duplicating Albany Slip
Duplicating AP Green Fireclay
Electric Hobby Kilns: What You Need to Know
Fighting the Glaze Dragon
Firing Clay Test Bars
Firing: What Happens to Ceramic Ware in a Firing Kiln
First You See It Then You Don't: Raku Glaze Stability
Fixing a glaze that does not stay in suspension
Formulating a body using clays native to your area
Formulating a Clear Glaze Compatible with Chrome-Tin Stains
Formulating a Porcelain
Formulating Ash and Native-Material Glazes
G1214M Cone 5-7 20x5 Glossy Base Glaze
G1214W Cone 6 Transparent Base Glaze
G1214Z Cone 6 Matte Base Glaze
G1916M Cone 06-04 Base Glaze
G1947U/G2571A Cone 10/10R Base Matte/Glossy Glazes
Getting the Glaze Color You Want: Working With Stains
Glaze and Body Pigments and Stains in the Ceramic Tile Industry
Glaze Chemistry Basics - Formula, Analysis, Mole%, Unity, LOI
Glaze chemistry using a frit of approximate analysis
Glaze Recipes: Formulate Your Own Instead
Glaze Types, Formulation and Application in the Tile Industry
Having Your Glaze Tested for Toxic Metal Release
High Gloss Glazes
How a Material Chemical Analysis is Done
How desktop INSIGHT Deals With Unity, LOI and Formula Weight
How to Find and Test Your Own Native Clays
How to Liner-Glaze a Mug
I've Always Done It This Way!
Inkjet Decoration of Ceramic Tiles
Is Your Fired Ware Safe?
Leaching Cone 6 Glaze Case Study
Limit Formulas and Target Formulas
Low Budget Testing of the Raw and Fired Properties of a Glaze

Make Your Own Ball Mill Stand
Making Glaze Testing Cones
Monoporosa or Single Fired Wall Tiles
Organic Matter in Clays: Detailed Overview
Outdoor Weather Resistant Ceramics
Overview of Paper Clay
Painting Glazes Rather Than Dipping or Spraying
Particle Size Distribution of Ceramic Powders
Porcelain Tile, Vitrified or Granito Tile
Rationalizing Conflicting Opinions About Plasticity
Ravenscrag Slip is Born
Recylcing Scrap Clay
Reducing the Firing Temperature of a Glaze From Cone 10 to 6
Single Fire Glazing
Soluble Salts in Minerals: Detailed Overview
Some Keys to Dealing With Firing Cracks
Stoneware Casting Body Recipes
Substituting Cornwall Stone
Super-Refined Terra Sigillata
The Chemistry, Physics and Manufacturing of Glaze Frits
The Effect of Glaze Fit on Fired Ware Strength
The Four Levels on Which to View Ceramic Glazes
The Majolica Earthenware Process
The Physics of Clay Bodies
The Potter's Prayer
The Right Chemistry for a Cone 6 MgO Matte
The Trials of Being the Only Technical Person in the Club
The Whining Stops Here: A Realistic Look at Clay Bodies
Those Unlabelled Bags and Buckets
Tiles and Mosaics for Potters
Toxicity of Firebricks Used in Ovens
Trafficking in Glaze Recipes
Understanding Ceramic Materials
Understanding Ceramic Oxides
Understanding Glaze Slurry Properties
Understanding the Deflocculation Process in Slip Casting
Understanding the Terra Cotta Slip Casting Recipes In North America
Understanding Thermal Expansion in Ceramic Glazes
Unwanted Crystallization in a Cone 6 Glaze
Variegating Glazes
Volcanic Ash
What Determines a Glaze's Firing Temperature?
What is a Mole, Checking Out the Mole
What is the Glaze Dragon?
Where do I start in understanding glazes?
Why Textbook Glazes Are So Difficult

Low Fire White Talc Casting Body Recipe


The classic white ball clay talc casting and modelling recipe has been used for many years. It is a dream to use as long as you are aware of the problems and risks.


When you buy a low temperature white burning body from a ceramic supplier you are buying what the industry calls a 'talc body'. Talc bodies are basically 50% ball clay and 50% talc (variations are discussed below). If your supplier says the recipe is a secret, let it pass, everyone is entitled to their beliefs. On the other hand, some suppliers have gone through a lot of effort to choose the best ball clay and talc available in their area and they might be putting in a small amount of other things. The ball clay in this body gives it great dry strength for handling and the talc imparts the good casting, drying and glaze fit properties (more on that in a minute). The use of this type of body started in the hobby casting industry and it became a standard on which the prepared glaze industry could rely. They created all of their products to fit this type of body. This standardization was a big reason for the success of what the commercial ceramic manufacturing industry would regard as an unorthodox and problematic recipe. However hobby cast ware has even thicknesses and is fired relatively slowly in top loading kilns so the body does not suffer process related failures that large industrial users would encounter (firing cracks, glaze crazing). Almost anyone can cast it successfully and very difficult shapes can be made because of its high wet and drying strength. It has both a fast casting rate and good strength (qualities not normally found together). Talc bodies are also very stable when fired to cone 05-06, they do not warp, even on thin pieces. So again, hobbyists with no knowledge of ceramic manufacture can make complex overhung shapes and never even think about warping issues. Another factor is that talc bodies often fire amazingly white compared to stonewares and thus bright colored glazes work well on them.

Manufacturers of modelling, throwing and sculpture bodies figured out that this 50:50 talc:ball clay recipe could be adapted to plastic forming by simply adding a little bentonite to improve plasticity. Such bodies have the best throwing properties, for example, of any clay available. The beauty of this adaptation is that the whole world of prepared glazes is then available to potters and sculptors.

The Down Side

There has to be some downside to this. There is.

Firing and fired properties had to be compromised to get the easy working properties. Firing is done at cone 06, that is a very low temperature, there is no getting around it. Pieces are weak, you can rip them apart with your bare hands easily. They are completely unsuitable for functional uses. You can fire higher to get more strength but you will not find commercial glazes to fit. And if you fire too high (e.g. cone 02) the ware can become brittle with some ball clay:talc combinations (others can survive to cone 6 amazingly).

Talc bodies fire white simply because there is no glass development taking place, no 'glue' is forming to cement the matrix together (that is why pieces are weak). However if you fire a talc body higher the color darkens dramatically because glass development brings out the color of the iron.

These bodies have 50% ball clay, there is no getting around it. Ball clay by itself will shiver almost any glaze on the planet. Ball clay contains lots of free quartz, each quartz particle 'throws tantrums' when heated and cooled through 1060F (sudden expansion and contraction of up to 5%). If you have enough of these particles they impose their character on the whole matrix. In addition, micro-cracks radiate outward from each grain of quartz and the degree of cracking varies geometrically with grain size. Micro-cracks become mega cracks if firing is too quick or pieces have too much variation in thickness.

Glaze fit: Glaze is just not 'glued on' very well. Therefore crazing and shivering will occur with much smaller differences in body and glaze thermal expansion than in stoneware where there is a highly develop clay/glaze interface.

Food Safety: Low fire glazes are much more soluble and prone to leaching and they are not nearly as hard a strong. But they look good, right!

Porosity: Low fire bodies are porous, up to 15% air space! Than means they will soak up water like a sponge. If a piece stays wet it can breed bacteria. If the water gets between two glazed walls it can explode a piece when it turns to steam during heating.

So, low fire talc bodies are a bit of a king-with-no-clothes situation (complete with a crowd of people so absorbed with the whiteness that they overlook the problems with the whole process). These bodies pretend to be ceramic with fancy glossy glazes but underneath they are porous and weak and there unceramic.

The Materials

Talc is used in low fire hobby bodies for several reasons:

It increases the thermal expansion. Without the talc it is very difficult to create glazes with a low enough thermal expansion to prevent crazing on typical clay bodies made from clay, feldspar and quartz. So adding talc was a no-brainer. You must realize however that this creates possible problems. If the body expands more on heatup (and therefore contracts more on cool down) then you are going to have more firing cracks if there are gradients in the ware (variations in thickness that cause variations in temperature across the cross section during heat up/cool down).

Talc is white and therefore a good major ingredient in a white burning body. I should correct that. Some talcs are white and some fire very yellowish or even brownish. Therefore, if you are formulating your own body, try many different talcs to find the whitest one. However take into consideration that the whitest one might not be the most consistent one. A good policy is to use two or more talcs in a recipe to dilute the effects of changes in one of them.

Another thing to keep in mind is that there are a lot of differences in the mineralogies of different talcs. It is quite remarkable how different they can behave in terms of melting, expansion, color, working properties. One thing to be especially aware of: Some talcs are much more temperature volatile than others and will cause a body to liquefy if over fired too much, others will be more temperature stable.

Ball clay imparts plasticity to clay bodies. It is much too plastic to use by itself, thus it is mixed with other materials. Talc is an ideal complement to ball clay to create a dryable body that still has excellent working properties (one of the primary reasons is its particle shape). People used to using porcelains and stoneware are often surprised at the feel of a talc body.

High-ball clay bodies are not used in industry because of drying and firing cracks and glaze shivering (from the high quartz content), but in the hobby casting market it works because of the 50% talc to dilute the problematic effects of high ball clay. So if you use talc bodies, you just need to be aware that you are using a body that industry could not use because you are willing to shepherd it through the process slower and get a weaker more porous fired product than what they are willing to tolerate.

Ball clays are dirty (high in iron) compared to kaolins. However they are so much more plastic that the iron is considered tolerable. However in talc bodies it is normal to use the whitest ball clays available, especially those that have low soluble salts content (which can produce an off-color scum on the fired surface).

Since ball clays are a natural mined product they are usually just blended, ground and sold. That means there is variation in their chemistry and mineralogy (and also particle size if the manufacturer is not vigilant). Thus it is best if your talc body employs more than one ball clay to dilute the effects of changes in any one of them. Ask your supplier if this is the case (if you are using a prepared clay body).

Bentonite is ball clay on steroids! It adds a lot of plasticity for a little addition. Bentonite is also dirty (high in red burning iron), the more you use the darker the body will fire (white bentonites are not plastic enough and they are too expensive, forget about them for this use). Do not put bentonite in the casting version of this body, the casting rate will slow down dramatically.

Whiting or Calcium Carbonate: Many talc bodies have small additions of this (e.g. 5%). Many people think it is used to whiten the color, but not so. Whiting reduces a phenomenon called 'moisture expansion' that occurs in low firing porous bodies when they soak up water. This expansion causes a glaze that was otherwise fitting to be stretched and therefore craze.


The ideal firing circumstance is that every section of a piece be at the same temperature throughout the firing. When this is true you can fire very fast. However if the kiln is not heating evenly, for example, part of a piece will get ahead of the rest on heatup. As the piece goes through critical temperatures at which sudden expansion occurs the variation in temperatures across it will translate into waves of expansion moving across it. When these waves hit weak or thinner sections, something has to give.

If a piece has widely varying thickness across its cross section, then on cool down of the kiln the thicker sections are going to lag behind. As above, waves of expansion change will travel across the piece and crack it.

As if the above are not enough to worry about, remember that talc bodies are made from materials susceptible to this issue. Together they create a body designed have a high expansion. It sounds like a recipe for cracks for the unwary. If it were not for its open and porous nature to stop the majority of microcracks (at the nearest pore) talc bodies would be much more prone to cracking.

So if you are forming ware using a technique that produces wide variations in thickness (e.g. throwing, pressing) be wary.


Talc is a magnesium silicate, either fibrous (like asbestos) or platy (like kaolin). Platy talcs are the ones that are useful in ceramics and producers make great efforts to insure the purity of their products (platy only). Ball clays contain significant quartz. These clay bodies are a mixture of these two materials. So caution is needed, be aware and careful.

Testing and Adapting

Can you test incoming body stocks for problems? Yes, you must. The low fire process has so many advantages but remember: it has costs. The biggest single issue is likely glaze fit, crazing and shivering are so much more common than with stoneware. You really should glaze test pieces and then stress them using a boiling water:ice water test. At the first sign of a problem adjust your glaze accordingly. If you are using a commercial glaze contact your supplier to make sure they have a strategy to do this (e.g. mixing two base glazes, using an additive). If you make your own glaze use a selection of high and low expansion frits so you can trade them off against each other to adjust expansion to adapt.

Check incoming material for large quartz grains. You can do this by simply washing some of the material through a 325 screen. Larger quartz particles will be immediately evident. Their presence can give you an alert to call the supplier and to watch your firing.

Do a test firing for color. If it is darker this could be an alert that your supplier has changed talcs. If it is lighter or darker they might have changed ball clays. This could mean that other working and firing characteristic could be affected.

The Recipe

Use this recipe as a starting point. For the casting version start using the amount of water and deflocculant shown. Note that slip casting recipes that show water and deflocculant do so in terms of the total clay content. Thus 45% water means that for 100 pounds of clay you need 45 lbs of water.

A Typical cone 06-04 Ceramic Slip

Talc 50.0
Ball Clay 50.0
Water 45.0% of dry amt
Soda Ash 0.1% of dry amt
Sodium Silicate 0.2-0.4% of dry amt

For the modelling version add bentonite (up to 5%). Use the most plastic bentonite you can find, do not worry about the fired color, 5% of even a dark brown firing bentonite should not change the color of the body much.

Use more than one ball clay and talc if you can (to insulate changes).

If crazing is a perennial problem, then use more talc and less ball clay (some people use a 60:40 talc:ball clay mix for casting. However if you are using the modelling version with added bentonite, think carefully before cutting the ball clay to 40%, it is needed for plasticity.

Consider adding some whiting to prevent moisture expansion and a small amount of barium carbonate (0.3%) to precipitate soluble salts. If you are adventurous, consider swapping some of the ball clay for kaolin, it is a much whiter, more water permeable but less plastic clay.

Things to Watch Out For

If you want to fire higher for more strength beware that the body will be darker in color (there is still lots of iron in even the cleanest talcs and ball clays and higher temperatures form glasses that reveal its presence).

Ware is normally very resistant to warping when fired at the typical cone 06-04. But do not get crazy, drastically overhung pieces can warp. Of course there is a big disadvantage to stability in the kiln: at these low temperatures ware is very weak and porous, thin ware can often be torn apart with your bare hands. You can burn to cone 03-02 or maybe even as high as 1 (but no higher) and get huge increases in strength but you will not be able to use commercial glazes, you will have to formulate your own (the frit companies can help you with a recipe, get them to give you a low and high expansion frit so you can trade them off for each other to adjust thermal expansion if needed). Don't even think about firing to cone 6, talc:clay mixes can melt suddenly and completely ruin your kiln. In addition, they can produce a very brittle matrix. In addition, from 1100 C on talc decomposes and releases H20 that cause lots of bubbles in glazes.

Slips, engobes: At low temperatures these may not stick to the body very well at all. If the thermal expansion of your glaze and clay body are not matched well, the glaze will simply part ways with the body at the slip or engobe buffer layer. Underglazes should be OK as long as they melt well, are not too thick and they have a matching thermal expansion.

What Will You Do?

Talc bodies are fine as long as you use them within the universe for which they were designed. All those flashy commercial glazes are pretty compelling. If you do not have any compunction to understand how glazes or clay bodies work then don't worry, be happy.

But if you working outside the 'hobby ceramics box' then beware. You need to know the limitations of what you are using. If you run into problems it is likely not the fault of the body manufacturer. He is assuming that you know the talc body and the world it is in the center of. If you are at the edges of that world then you are on your own.

On the other hand you might be wanting to dig deeper with the objective of making stronger ware. Think about firing to at least cone 02 (where stoneware strength can be achieved using terra cotta bodies). Learn to make your own glaze that you can adjust and control. Lots of prepared low fire bodies will fire to cone 02 easily. If you mix your own clay body then you are in an ideal position to change to a different recipe that will produce stronger and more functional ware.

Related Information

How is it possible for the same body to work well at both cone 04 and 6!

The same clay body fits glazes at low temperature and is a stoneware at medium fire. How?

Plainsman 3D! White cone 04 bodies are not vitreous and strong and neither is this. But it is plastic, smooth and fits common low fire glazes. How? 15% Nepheline Syenite (also 50% Plainsman 3D, 35% ball clay and 3% bentonite). The unmelted nepheline particles impose their higher thermal expansion on the fired ceramic. Spectrum 700 clear glaze does not craze and does not permit the entry of water (the mug is glazed across the bottom and fired on a stilt). The mug on the right is made from the same clay, it has been fired ten cones higher, cone 6! Here the nepheline is acting as a flux, producing a dense and very strong stoneware (with G2926B, GA6-B glazes). This is incredible! One note: This cannot be deflocculated and used for casting, soluble salts in the 3D gel the slurry.

The high thermal expansion of a low-fire talc body

Talc is employed in low fire bodies to raise their thermal expansion (to put the squeeze on glazes to prevent crazing). These dilatometer curves make it very clear just how effective that strategy is! The talc body was fired at cone 04, the stoneware at cone 6. The former is porous and completely non-vitreous, the latter is semi vitreous. This demonstrates something else interesting: The impracticality of calculating the thermal expansion of clay bodies based on their oxide chemistry. Talc sources MgO and low fire bodies containing it would calculate to a low thermal expansion. But the opposite happens. Why? Because these bodies are composed of mineral particles loosely sintered together. A few melt somewhat, some change their mineral form, most remain unchanged. The body's COE is the additive sum of the proportionate populations of all the particles. Good luck calculating that!


Articles Understanding the Terra Cotta Slip Casting Recipes In North America
This article helps you understand a good recipe for a red casting body so that you will have control and adjustability.
Articles G1916M Cone 06-04 Base Glaze
This is a frit based boron base glaze that is easily adjustable in thermal expansion, a good base for color and a starting point to go on to more specialized glazes.
Articles Adjusting Glaze Expansion by Calculation to Solve Shivering
This page demonstrates how you might use INSIGHT software to do calculations that will help you increase the thermal expansion of a glaze while having minimal impact on other properties.
Articles Understanding Thermal Expansion in Ceramic Glazes
Understanding thermal expansion is the key to dealing with crazing or shivering. There is a rich mans and poor mans way to fit glazes, the latter might be better.
Articles Understanding the Deflocculation Process in Slip Casting
Understanding the magic of deflocculation and how to measure specific gravity and viscosity, and how to interpret the results of these tests to adjust the slip, these are the key to controlling a casting process.
Articles Stoneware Casting Body Recipes
Some starting recipes for stoneware and porcelain with information on how to adjust and adapt them
Glossary Low Temperature Glaze Recipes
In ceramics, glazes are loosely classified as low, medium and high temperature. Low temperature is in the cone 06-2 range (about 1800F-2000F).
Glossary Deflocculation
The deflocculation process is the magic behind the ceramic casting process. It enables you to make a slurry of far lower water content and thus lower shrinkage.
Materials Ball Clay
Materials Talc
Replace Talc with Nepheline Syenite in low temperature white bodies
This is a development project at Plainsman Clays. It is in response to Texas talc no longer being available in North America.

By Tony Hansen

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