• Materials for Ceramics

Tile #6 Kaolin

Alternate Names: Tile 6, Tile#6 Kaolin, #6 Tile kaolin

Description: Highly Plastic Fine Grained

Notes

#6 Tile is an air-floated highly plastic kaolin. It thus offers high green strength. No other kaolin we know of in the world even comes close to the plasticity of this material. A cone 10 porcelain can be made using a 50:25:25 recipe of this with silica and feldspar. With a small bentonite addition, bodies can be made that are plastic enough for wheel-throwing gigantic vessels. #6 tile is thus also good for suspending glazes. However, this material is relatively impermeable to water compared to other kaolins, it is thus the last choice for casting bodies.

#6 Tile kaolin fires to respectable whiteness and compares well with most other North American kaolins. It is an excellent example of one having properties that cannot be fully appreciated from numbers on a data sheet, it is only by getting your hands dirty that its properties will become truly evident.

#6 Tile kaolin has been available for many decades and the consistency has been quite good.

Particle size, % < 2 microns 60
325 mesh screen residue, % max 0.5
M.B.I. (meq/100g) 9.8
Specific Surface Area (sq-m/g) 20.0
pH, 20% solids 6.5
*The information given here is from their data sheet dated Jan 2013

Related Information

The most plastic kaolin in North America. Likely the world.

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#6 Tile kaolin is a "designer kaolin", they add bentonite to the material during manufacture to increase the plasticity far beyond what mother nature can make. This vase is made from the pure kaolin, it is very thin-walled and light, this would be impossible with almost any other kaolin. The fired colour is darker than some other North American kaolins but much less of this and less added bentonite is required in a recipe to get the same plasticity. Thus, in the end, a plastic porcelain body can often fire just as white using this as other whiter burning kaolins.

A Grolleg based porcelain vs. a ball clay and American kaolin porcelain

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These mugs were fired in the same kiln load at cone 10R and have the same clear glaze, G1947U. The mug on the left is a Grolleg kaolin (52% Grolleg kaolin, 24% silica and 19% Mahavir feldspar, 5% bentonite). The one on the right is 15% M23 ball clay, 40% #6 Tile kaolin, 15% Nepheline, 25% silica, 3% bentonite. Clearly, the Grolleg porcelain fires so much whiter.

Rear of #6 Tile kaolin original container bag

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From 2022 as received at Plainsman Clays.

#6 Tile Kaolin 2021 vs EP Kaolin 2020: Fired properties tell an unexpected story

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These test bars are fired at cone 10 reduction (top) and 10, 9 and 8 oxidation (downward) - they demonstrate the importance of measuring physical properties. The charts for each show data for drying shrinkage, firing shrinkage and porosity (water absorption). The left bars are #6 Tile kaolin and the right are EPK. These two kaolins had almost the same drying shrinkages in this SHAB test, that suggests the same plasticity. And the EPK fires whiter. So it should make a better plastic porcelain, right? Not so. In reality, #6 Tile kaolin is far more plastic - EPK requires the addition of significant bentonite to equal it (bentonite is dirty and that compromises whiteness). And EPK fires less vitreous - when feldspar is added color darkens. And, although both have extremely high firing shrinkages, the EPK is much higher than the #6 Tile (even though it is not as vitreous). Bottom line: #6 Tile is a better kaolin for clay bodies.

What made EP Kaolin unique?

Are others as good?

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In ceramics, EPK, or EP Kaolin, is used in clay bodies and glazes. EPK feels fairly plastic on wedging. But it splits like this during throwing (top right). It needs the help of bentonite or ball clay to be usable in porcelain or stoneware bodies. Tile #6 kaolin is thus far better choice for plasticity (although higher in iron and titania).

But EPK shines in glazes. A slurry of pure EPK (bottom), mixed to only 1.15 specific gravity, holds this spatula upright! Glazes employing as little as 20% EPK, without added electrolytes, are naturally thixotropic. And its sticky nature helps with adherence and dry hardness. Consider the engobe employing it (top left). It gels and clings to this rubber spatula in an even layer, with no drips. If leather-hard ware is carefully dipped into it, upon extraction it stays put (even if it takes hours to dry). The performance of EPK suspending glazes for use on bisque is even better.

Are there other sticky kaolins that gel? Yes. Grolleg and New Zealand kaolin. What if you cannot get either? Tile #6 is a good choice because it dries hard. But, it may need the help of Epsom Salts to produce a slurry having thixotropy like EPK.

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