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Grolleg Kaolin
Fine White Burning English Kaolin, English China Clay
Chemistry
Chemistry available on new site, see link above
Mineralogy
- Mica: 15
- Kaolinite: 81
- Feldspar: 1
Links to Other Materials
- Standard Porcelain Kaolin - Related
- NSC Kaolin - Related
- Remblend Kaolin - Related
- Treviscoe Kaolin - Related
- Super Standard Porcelain - Related
- Kaolin - Parent
- Cache
Miscellaneous
- Family: Kaolin
- Region: North America
- Mined At: Unspecified
- Raw Mineral: No
- Generic: No
Notes
A blended English china clay, combining moderate plasticity, low titania content and relatively high flux content, low shrinkage and white fired color. It is excellent for making translucent throwing or casting porcelains. The pottery community uses many Grolleg based porcelains.
Its chemistry is different from a typical North American kaolin, it contains some fluxing oxides (e.g. it has almost 2% K2O). Thus porcelain bodies employing it require slightly less feldspar to vitrify.
For use in plastic porcelains there is dilemma that body formulators face: This material has a much lower plasticity than materials like #6 Tile and Sapphire kaolin. Thus porcelain bodies employing it require additions of a plasticizer like bentonite, in some cases up to 5%. Since bentonites having the necessary plasticity are also exceptionally high in iron, North Americans must balance the advantages of using a white burning and more costly material like this against the low plasticity that makes the addition of dirty plasticizers necessary. The low TiO2 content is a key factor for its usefulness in making translucent bodies and even 5% bentonite having 5% iron content will only increase iron in the body by 0.25%. However if plasticity and whiteness are important and translucency is secondary, you might find that more plastic kaolins are better for plastic bodies.
Glazes: While the chemistry difference between this and more typical kaolins is certainly worth noting for bodies, it is still likely close enough to the theoretical 1 alumina and 2 silica to be used in glazes that call for kaolin or china clay. However there may be exceptions where the titania in other kaolins could be detrimental to the development of a color (titanium can turn celedons to a greenish tint).
Modulus of Rupture, Kgf/cm2
At 80% Relative Humidity: 10.0
Dried at 110C: 25.7
Casting Rate @ 63% solids (mm2/min): 0.8
% P84 Deflocculant Required for 5 Poise Slip: 0.65
1180C 1280C 1410C
Brightness: 86 86 75
Properties
Body Maturity -
The use of kaolins containing significant alkalies is an excellent way to achieve greater body maturity coupled with white color. Lower feldspar enables replacing dirty ball clays with kaolin.
Data
- Ultimate Particle Size Distribution
>53 microns .05 max
>10 microns 10
<2 microns 57 - Water absorption
1180C 14%
1280C 6%
1410C 0.5% - Firing Shrinkage
1180C 0%
1280C 14%
1410C 18% - Melting Point (MP): 3000F
- Melting Point (MP): 3000F
- Firing Shrinkage
1180C 0%
1280C 14%
1410C 18% - Water absorption
1180C 14%
1280C 6%
1410C 0.5% - Ultimate Particle Size Distribution
>53 microns .05 max
>10 microns 10
<2 microns 57
Suppliers
- ECC
- Imerys
Authors
- Tony Hansen (Owner)
XML
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