Stuart Altmann on sat 20 dec 97
Paul Lewing:
Is your offer of some superfine SiC in exchange for a good local reduction
copper red still open? In any case, here are some contributions to this
topic, first a couple of methods from Baggs and Littlefield's original
article on this topic (American Ceramic Society Journal 15:265, 1932), then
a glaze called ZGP. I've used ZGP and it works, though the amount of red
area in the white background varies unpredictably (by me, anyway)
Baggs and Littlefield's first method puts the silicon carbide in the glaze,
the second in a slip under the glaze.
Method I.
Glaze:
raw borax 16.5
SS-20 powdered sodium silicate 5.55
feldspar 36.06
whiting 8.63
kaolin 16.70
flint 16.50
For red, make batch additions of 0.3% copper carbonate, 1% silicon carbide,
1% stannic acid. For blue (use as background to the red glaze), 5-7%
stannic acid, 0.3-1% copper carbonate. Fire to ^9 in oxidation.
Method II
White earthenware body used as a base slip with additions of 0.5-2.5%
silicon carbide. Bisqued to ^3, glazed (see below), then fired to ^9 in
oxidation.
Glaze:
feldspar 40.0
flint 40.0
borax 12.0
whiting 18.0
copper carbonate 0.6
tin oxide 2.0
Here's the recipe for ZGP red glaze. Use on
porcelain (or white stoneware). Amount of red might be increased
by slight increase in copper, addition of small amount of
mangagese dioxide, which ma! potentiate the red, by use of finer
silicon carbide (mine is 400 mesh), and by slight adjustments in
glaze thickness and firing temperature.
ZGP glaze (Local-reduction red. Fire to cone 9 in oxidation.)
Kona F4 2748
whiting 720
talc 300
zinc ox 300
EPK 360
flint 600
tin 36
copper carbonate 10
silicon carbide 18
frit 3134 120
bentonite 60
Good luck!
Stuar! Altman!
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