Tom Buck on wed 30 oct 96
Recently, a glaze recipe for satin black was posted here with a
request for revision to C6 brown in oxidation. Here is such a recipe:
C6 Base Glaze, oxidation or reduction
24.0 Custer feldspar (or equal, eg, G-200 f.s.)
19.0 Kona F-4 feldspar
14.0 Wollastonite
11.0 Talc
12.0 OM#4 ballclay or equal (eg, Bell Dark)
20.0 Flint (fine mesh)
Add 2-5% iron oxide red for browns; 1-2% Cobalt carbonate for blues; 2-4%
Copper carbonate for greens. Try other colourants for variation. On some
bodies, the glaze may require a 30-minute soaking.
The Seger formula for the revision above is:
CaO 0.51; MgO 0.24; KNaO 0.25; Al2O3 0.40; SiO2 4.10
which places the glaze in the middle of the 3-7 cone range. The glaze
will be glossy Ratio = 10.3 and it should fit most stoneware bodies,
perhaps even some porcelaineous stonewares since the Expansion
coefficient is 6.6x10-6.
The original glaze as cited was relying on the high level of
colourant oxides to help bring it closer to balance but it would be
overfired at C9 (if the body fails to release silica to the glaze).
Tom Buck Hamilton ON Canada URL http://digitalfire.com/magic/tombuck.htm
| |
|
