RAW MATERIALS AND OXIDES
RAW MATERIALS AND OXIDES

REFSAN KAOLIN GROLLEG (5319)

Brand : REFSAN
Price : 11,25TL
ÇOKALAZÖDE BOYA

 

GROLLEG KAOLIN

A blended English china clay, combining moderate plasticity, low titania content and relatively high flux content, low shrinkage and blue-white fired color. The low TiO2 content is a key factor for the usefulness of Grolleg. 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 quite less feldspar to vitrify (5-10% at cone 10, for example).

For use in plastic porcelains there is dilemma that body formulators face: This material has a lower plasticity than American materials like EPK and much lower than #6 Tile and Sapphire kaolins. Thus porcelain bodies employing it require additions of a plasticizer like bentonite (up to 5% to get high plasticity). Since raw bentonites having the necessary plasticity are also exceptionally high in iron, people must balance the advantages of using a white burning and more costly material like Grolleg against the lower plasticity that makes the addition of dirty plasticizers necessary. Theoretically making translucent bodies employing 5% bentonite having 5% iron content should only increase iron in the body by 0.25%. This does not sound like much, but it is. Bodies having 0.1% iron burn much whiter than those having 0.2%. Thus either lower plasticity should be tolerated or white plasticizers (like VeeGum or Bentone) should be used.

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 1:2 alumina:silica to be substituted in recipes that call for kaolin or china clay. Grolleg may also be preferred because the titania in other kaolins is detrimental to the development of a color (titanium can turn celedons to a greenish tint). Transparent glazes employing Grolleg as-the-kaolin used over Grolleg-based porcelains can produce very white and even blue-white color in reduction firing. Another factor making this material an excellent glaze suspender is its inherent stickiness, which is exhibited to a degree much in excess of its actual plasticity. This property also makes for great hardening and durability of the dried glaze layer.

 

 

GROLLEG KAOLIN

1.  CHEMICAL ANALYSIS

 

A.Z.

(%)

SiO2 (%)

Al2O3 (%)

Fe2O3 (%)

TiO2 (%)

CaO (%)

MgO (%)

Na2O (%)

K2O (%)

 

12.00

 

49.00

 

36.00

 

0.75

 

0.02

 

0.06

 

0.30

 

0.10

 

1.85

 

2.  GRAIN SIZE DISPERSION %

 

+53 micron

0.05

+8 micron

8.00

-2 micron

58.00

 

3.  MINERALOGICAL ANALYSIS %

 

Kaolinit

86.00

Mica Like Material

10.00

Feldspar

2.00

Other Minerals

2.00

 

4.  BREAKING RESISTANCE

 

80 moisturized

MNm -2

1.00

 

p.s.i.

140

Dry at 110°C

MNm -2

2.60

 

p.s.i.

365