5. Jim Cooper's Translucent Porcelain AlO-11

Grolleg nO Custer feldspar 12.5 F-4 feldspar 12.5 Nepheline Syenite 5 Pyrophyilite 5 200 mesh allica _15

100

Add: 2% Veegum T. 0.3% Epsom Salts (156 grams per 100 Ibs. dry material).

Nepheline Syenite: A sodium based feld- spar. All sodium-based feldspars such as F-4, NC-4, Minspar, and nepheline syenite melt approximately twice as fast as potash-based feldspars such as Primus, Norfloat, Custer, G-200 and K Spar. Sodium is a more active alkall than potassium producing a lower vis- cosity glass which takes other materials in the body into the melt somewhat faster than potash feldspars. (I have not found deflocculation problems usingJim Cooper's Porcelain, perhaps because | use acidic water for mixing clay.)

I have found reduced warping and slumping with Jim Cooper's Porcelain in comparison with other highly fluxed porcelains containing 30% feldspar. Yet even a lightweight attached handle on a thin-walled cup will pull the cup out-of- round at Come 10, using this clay body.

This ts the first of two parts of an article which first appeared in the most recent issue of The Studio Potters’ Network. It has been revised by Davidl as a result of Jurther testing on his part. Part 2 will be printed in Januany and covers testing and micing of the aboue recipes. Thanks to Studio Potters’ Network and to David Beumdée, He ts a member of the Boulder Potters' Guild. Address: 806 E. Baseline, Lafayette, CO 80028,

Table: Properties of Tested Clays

Workability | Transiucency

Absorption

Whitenses at Cone 10

Shrinkage at Cone 10

Excellent Very Lintle

Stighth Oreyed

1a

OTS 110

Excelbernt

Slight

Excellerit

Excellent

1?

GTS 3-10

Exeelent Almost None

14%)

GTS 2-10

Excellent Very Stight

None

17%

GTS 2-10

Excellent Excellent

Exeellent Slight

Slight

17.

GTS 3-10

December, 1991

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