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Ball Clay

Oxide Analysis Formula
CaO 0.30% 0.02
K2O 0.90% 0.04
MgO 0.30% 0.03
Na2O 0.40% 0.03
TiO2 1.00% 0.05
Al2O3 25.00% 1.00
SiO2 59.00% 4.01
Fe2O3 1.00% 0.03
Oxide Weight 358.63
Formula Weight 407.54


The term 'ball' traces to historic mining in England where large chunks of the clay were cut from the bank in ball shapes for transport to processing. There are hundreds of different ball clays available. Potentially they should vary widely in plasticity, particle size, raw color, and drying properties. But in practice, most are remarkably similar. A typical ball clay powder is light grey (from lignite) or cream color and fires to a buff or cream (with some soluble salt deposits on the fired surface). Ball clays tend to be quite refractory (PCE 28-34) and some less processed deposits are sold as fireclays. Ball clay is not a clay mineral in itself, but contains other minerals, primarily kaolinite (but also montmorillonite, halloysite, and illite). Mica and quartz are also present in substantial amounts (e.g. 10-20% for Tennessee ball clays).

Ball clays are very plastic and much finer-grained than kaolins. They are easily slaked in water when dry. Few people fully appreciate how 'sticky' and plastic these materials are until they mix some with water and work with it pure. The fine particle size also makes them impermeable to the passage of water (a small test bar can take a very long time to dry).

While potters only buy ball clay as a powder, industrial users have access to the material in many forms (shredded, noodled and partially deflocculated, chopped filter press cake, vacuum pugged extrusion, crumble with about 10% moisture). These forms enable a more consistent supply and alot of flexibility, especially when making casting slips (since ball clays are the most difficult to disperse materials in the bodies).

They are typically unvitrified at cone 10. There are a wide range of ball clays used in traditional ceramic manufacture in North American and they have surprisingly similar firing characteristics (maturity and color). In one test we made 50:50 ball clay:feldspar mixes of 8 different common ball clays (from a range of suppliers), from cone 6 to 10 all had the same porosity and fired appearance.

Ball clays are used in ceramic bodies (porcelains, stonewares and earthenwares, casting slips, pressing bodies) because of their plastic nature combined with high firing temperature. Ball clays have very high dry shrinkage combined with high green strength and slow drying. Were it not for their iron and coal impurities, ball clays would be ideal ceramic materials. However, in practical terms, they are employed to achieve desired plasticity, but are minimized to reduce the detrimental effect on fired whiteness and drying properties.

A common starting recipe for a high temperature general purpose porcelain (as is used in electrical porcelain or extruded pottery porcelain is 25% each of ball clay, kaolin, feldspar and silica). The ball clay:kaolin mix can be altered to change body plasticity without significantly affecting the maturing temperature.

In North America, most commercial ball clays are mined in the southeastern US. Ball clay deposits are common and were laid by the action of slow moving water with an acidity that tended to flocculate and settle the clay. It is common to find lignite associated with ball clay, and this accounts for the almost grey appearance of many varieties (when wet).

It is difficult to compare their plasticities by quantitative tests because pure samples are difficult to mix and form (they are incredibly sticky) and crack badly during drying. Thus, it is common to mix ball clay and silica 50:50 and compare dry shrinkage, dry strength, soluble salts, fired color. Another technique to mix raw:calcine 50:50. In our testing of many ball clays, drying shrinkage and water of plasticity it very similar (those intended for casting have a little lower drying shrinkage, but they also fire very similar). In general it may be said that English ball clays tend to have a higher dry strength (and thus drying shrinkage) than American ones, Kentucky ball clays have the lowest carbonaceous matter, English ones vitrify lower, Tennessee ones fire whitest.

Although some ball clays resist deflocculation because of hostile soluble impurities, most deflocculate very well with sodium silicate and other equivalent dispersants. A wide range of ball clay slurries and slips are used in casting at all temperature ranges. One common recipe uses a simple 50:50 ball clay:talc mix (in the hobby casting market). The same mix is also dry pressed in the tile industry, and extruded for jiggering and wet processing in artware.

The refractories industry is a large user of ball clay. Common refractory materials lack plasticity and ball clay is used to help in forming and shape retention and to impart dry strength. The abrasives industry likewise uses it to bond aggregates until firing fuses the mass.

Engobes in the tile and brick industries are suspended, hardened, and adjusted to match body shrinkage by the addition of ball clay. Many pottery glazes contain ball clay to help suspend and harden them and control their shrinkage during drying (although some technicians prefer cleaner kaolins for this, claiming they gel the slurry better and prevent drip-drip during drying). It makes a big difference what ball clays are used, some produce a syrupy mess that settles while others produce a beautifully suspended creamy slurry. In North America, Old Hickory #5 and Old Hickory No. 1 Glaze ball clays work well in glazes. 10-15% ball clay should be enough to suspend a glaze, if there is any less add 1-2% bentonite. Recipes with 20% or more ball clay risk shrinking and cracking during drying.

If the iron or lignite content of ball clay is a problem, it is common to employ bentonite to reduce the ball clay requirements (5% bentonite can provide as much improvement in plasticity and dry strength as 25% ball clay). However, care is recommended to make sure a fine grade of bentonite is used to avoid fired specks (bentonite also burns darker).

Unlike a kaolin, it is difficult to establish a generic or theoretical analysis, we have provided one for a typical Kentucky ball clay.

If you use ball clay in your production there is good reason to be doing routine quality control to make sure it is remaining consistent. Ball clays are likely the most variable material you will have to deal with. They can sometimes have particulate impurities (especially lignite) and exhibit differences in soluble salts content, drying shrinkage, drying performance, fired maturity, fired color and behavior in slurries. Consider the SHAB test (see link below).

Adequate quartz content is an important factor in porcelain and whiteware bodies (it is an important structural element in the fired matrix and it is needed to prevent glaze crazing). Since ball clays contain quartz, it is possible to use less raw silica (quartz) powder in the recipe if ball clay percentages are high. Of course, the quartz grains in the ball clay are finer, so they will dissolve into the feldspar glass more readily.

Related Information

Cone 6 kaolin porcelain verses ball clay porcelain.

Typical porcelains are made using clay (for workability), feldspar (for fired maturity) and silica (for structural integrity and glaze fit). These cone 6 test bars demonstrate the fired color difference between using kaolin (top) and ball clay (bottom). The top one employs #6 Tile super plastic kaolin, but even with this it still needs a 3% bentonite addition for plasticity. The bottom one uses Old Hickory #5 and M23, these are very clean ball clays but still nowhere near the whiteness of kaolins. Plus, 1% bentonite was still needed to get adequate plasticity for throwing. Which is better? For workability and drying, the bottom one is much better. For fired appearance, the top one.

Even heavy soluble salts may not have a significant affect on the glaze


What if you just cannot solve a pinhole problem?


Watch out for iron particles in ball clays


The ball clay you use to suspend your glaze is important!

I poured 4 teaspoons of two glazes onto a non-absorbent butcher’s board and let them sit for a minute, then inclined the board. The one on the right employs Gleason Ball clay, the left one has Old Hickory #5 ball clay. Neither has any slurry property modifier addition. The one on the right has settled and on incline the watery upper is running off. The other has gelled and the whole thing is running downward slowly. Below I have begun to sponge them off, the one on the right is sticky. The most amazing thing about this: This difference appears despite that there is only 7% ball clay in the recipe.

Carbon burnout in a ball clay


Four North American ball clays fired at high temperature


The white one feels smoother, but it is actually far coarser. Why?


High drying shrinkage of Plainsman A2 ball clay (DFAC disk)






Ball clay vs. Kaolin porcelain at cone 6

Left: A porcelain that is plasticized using only ball clays (Spinx Gleason and Old Hickory #5). Right: Only kaolin (in this case Grolleg). Kaolins are much less plastic so bentonite (e.g. 2-5%) is typically needed to get good plasticity. The color can be alot whiter using a clean kaolin, but there are down sides. Kaolins have double the LOI of ball clays, so there are more gasses that potentially need to bubble up through the glaze (ball clay porcelains can produce brilliantly glassy and clean results in transparent glazes even at fast fire, while pure kaolins can produce tiny dimples in the glaze surface if firings are not soaked long enough). Kaolins plasticized by bentonite often do not dry as well as ball clays even though the drying shrinkage is usually less. Strangely, even though ball clays are so much harder and stronger in the dry state, a porcelain made using only ball clays often still needs some bentonite. If you do not need the very whitest result, it seems that a hibrid using both is still the best general purpose, low cost answer.


What would happen if you made a body from 50:50 kaolin:ball clay?

It would craze glazes! This is fired at cone 6 and the crazing was like this out of the kiln. This is about as bad as I have ever seen. One might think that there is adequate quartz in this high of a percentage of ball clay to at least minimize crazing, but no so. This demonstrates the need for adequate pure silica powder in stoneware bodies to give them high enough thermal expansion to squeeze glaze on cooling to prevent crazing like this. This is also not proving to be quite as refractory as I thought, it looks like it will have about 3% porosity at cone 10.

Ball clay powders are minus 200 mesh. Right? Wrong!


Two-material porcelain much better with ball clay than kaolin



The difference in fired character between kaolin and ball clay at cone 10R

The top one is EP Kaolin, the bottom one is Old Hickory M23 Ball Clay (these materials are typical of their respective types). These materials have low alkali contents (especially the kaolin), this lack of flux means they are theoretically highly refractory mixes of SiO2 and Al2O3. It is interesting that, although the kaolin has a much larger ultimate particle size, it is shrinking much more (23% total vs. 14%). This is even more unexpected since, given that it has a lower drying shrinkage, and should be more refractory. Further, the kaolin has a porosity of 0.5% vs. the ball clay's 1.5%. The kaolin should theoretically have a much higher porosity? What is more, both of these values are unexpectedly low. This can partly be explained by the particle packing achieved because of the fine particle size. Despite these observations, their refractory nature is ultimately proven by the fact that both of these can be fired much higher and they will only slowly densify toward zero porosity.

Health warning phrases on a bag of ball clay

Chunks of metal found in contaminated truckload of kaolin

You may not fully appreciate what your clay body manufacturer has to go through to make clean porcelain for you. Every load of material that they receive has to be checked. We now have to check every pallet. This is the third semi-trailer load of material we have had contaminated (ball clays and kaolins are most vulnerable). When we phoned another manufacturer they checked their supply and it was contaminated also! Materials can also be contaminated by larger clay particles that disrupt the fired glaze surface. These chunks of metal were pulled out by magnets in the production line, a thousand boxes of porcelain are now garbage. It is too expensive to return a load, so it just becomes a loss.

Cleanest kaolin porcelain vs. ball-clay-only porcelain!

Side by side mugs, a porcelain made using only kaolin and one made with ball clay

These cone 6 clear-glazed porcelains demonstrate just how white you can make a porcelain if you use white burning kaolins and bentonites instead of ball clays. Both contain about 40% clay. The one on the left employs New Zealand kaolin and Veegum plasticizer, the one on the right Kentucky ball clays (among the whitest of ball clays in North America) and standard bentonite. Both are zero porosity. The glaze surface is a little more flawless on the right one (possibly because ball clays have a lower LOI than kaolins).

Lignite contamination in manufactured porcelain bodies



Materials CTS Ball Clay
Materials Kaolin
Materials JASS Ball Clay
Materials 3380 Ball Clay
Materials RG1 Ball Clay
Materials Gizmo Ball Clay
Materials Kentucky #12
Materials Kentucky #6
Materials Royal Ball Clay
Materials Cooley No. 2 Ball Clay
Materials No. 5 Ball Clay
Materials Ball Clay FX (CA1)
Materials Ball Clay R
Materials Coppen Light Clay
Materials Crenshaw Ball Clay
Materials Cresan C Ball Clay
Materials Dresden M Ball Clay
Materials Eobb/y Ball Clay
Materials Esva Ball Clay
Materials EWVA Ball Clay
Materials F-2 Ball Clay
Materials Fayles Blue Ball
Materials Old Hickory FC340 Ball Clay
Materials FX Ball Clay
Materials Gresan C Ball Clay
Materials HB-11 Ball Clay
Materials HTP Ball Clay
Materials Huntingdon Ball Clay
Materials CDL Ball Clay
Materials CDI Ball Clay
Materials Bentonite
Materials BLUE-CLAY
Materials 44-B Ball Clay
Materials 49'er Ball Clay
Materials 5-S Ball Clay
Materials 54-S Ball Clay
Materials 56-S Ball Clay
Materials Anglo No. 1 Ball Clay
Materials No. 1 Ball Clay
Materials Bell Dark Ball Clay
Materials BKS/L Ball Clay
Materials C & C Ball Clay
Materials Caroso Ball Clay
Materials Caroso FC Ball Clay
Materials HVA/ND Ball Clay
Materials HVA/PM Ball Clay
Materials Texas GK Ball Clay
Materials Thomas Ball Clay
Materials TI-21 Ball Clay
Materials Todd Dark Ball Clay
Materials Todd Light Ball Clay
Materials TWVD Ball Clay
Materials Victoria Ball Clay
Materials Volunteer Ball Clay
Materials Yankee Ball Clay
Materials CP-7 Ball Clay
Materials Hyplas 64 Ball Clay
Materials J-4 Ball Clay
Materials HA-5 Ball Clay
Materials MB Ball Clay
Materials OSML Ball Clay
Materials Tennessee #9 Ball Clay
Materials Tennessee #6 Bond
Materials HVA/R Ball Clay
Materials Hymod AT Ball Clay
Materials Hyplas 71 Ball Clay
Materials Imperial Ball Clay
Materials J-2 Ball Clay
Materials Jackson Ball Clay
Materials Starcast Ball Clay
Materials Stratton Ball Clay
Materials SX Blue Ball Clay
Materials TA Ball Clay
Materials Taylor Blend
Materials TB-1 Ball Clay
Materials Tennessee #1 SGP
Materials Tennessee #10 Ball Clay
Materials Tennessee #5 Ball
Materials SB Ball Clay
Glossary Clay
What is clay? How is it different that regular dirt? For ceramics, the answer lies on the microscopic level with the particle shape, size and how the surfaces interact with water.
Glossary Deflocculation
Glossary Stoneware
To potters, stonewares are simply high temperature, non-white bodies fired to sufficient density to make functional ware that is strong and durable.
Glossary Plasticity
Plasticity (in ceramics) is a property exhibited by soft clay. Force exerted effects a change in shape and the clay exhibits no tendency to return to the old shape. Elasticity is the opposite.
Glossary Permeability
In ceramics, the permeability of clay slurries and plastics determines the rate as which water can move through the matrix
Tests Shrinkage/Absorption Test
Tests Sieve Analysis 35-325 Wet
Oxides C - Carbon
Oxides Al2O3 - Aluminum Oxide, Alumina
Hazards Ball Clay
Hazards Dioxins in Clays
DIOXINS in Clays used in ceramics, what are the dangers?
Hazards Dealing With Dust in Ceramics
A checklist for changes and additions to your tools and equipment and suggestions for habit you need to develop to control dust in your workplace.
Typecodes Ball Clay
Ball clays are abundant and very plastic and are used in all types of plastic forming bodies. They are not as white-burning or refractory as kaolins but lower in iron and fluxes than bentonites.
Typecodes Generic Material
Typecodes Ball Clay
Old Hickory Clays conference presentation on ball clays (educational)
Articles Formulating a Porcelain
The principles behind formulating a porcelain are quite simple. You just need to know the purpose of each material, a starting recipe and a testing regimen.
Articles Low Fire White Talc Casting Body Recipe



By Tony Hansen

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