Alisa Clausen on wed 4 jun 08
Recipe Name: Oil Spot Combo #2 Cover Glaze (Apply over #1)
Cone: 6 Color: Brown with white spots
Firing: Oxidation Surface: Oil Spot
Amount Ingredient
30 Feldspar--G-200
30 Gerstley Borate--1999
25 Silica
5 Kaolin--EPK
10 Zircopax
100 Total
Unity Oxide
.17 Na2O
.202 K2O
.001 MgO
.627 CaO
1.000 Total
.553 Al2O3
.655 B2O3
.003 Fe2O3
5.628 SiO2
.001 TiO2
0 P2O5
10.2 Ratio
5.9 Exp
Comments: Cover glaze #2 original and with subs. of both Frit 3134 and
local Boron Frit 169, all showed a good amount of spotting. The colorants
all showed well with the subs. The Frit 3134 revealed slightly brighter
colors than the G.B. and the Frit 169. Smooth surface with many spots and a
flat lichen appearance.
for colors of this glaze, add
Cu. Carb. 4% light green tint to cover glaze
Co. Carb. 4 % strong blue color to cover glaze
RIO (5-12%) 10% added brown to cover glaze
Still could see Rust brown #1 glaze under cover glazes. All have a good
contrast between both glazes.
Mixed cover glaze by subbing G. B. with
Frit 3134 and again with local Boran Frit 169.
No visible difference in glazes. Frit 3134 revealed a stronger blue in the
cover glaze #2 with Co. Carb.
Glaze test for Oil Spot Combo #2 Cover Glaze (Apply over #1) ^6 ox.
Source:
John Britt
Fired on mid fire white stoneware
Firing ramp with an electric controller is:
100c p/h to 600c (212f - 1112f)
150c p/h to 1140c (302f - 2084f)
80c p/h to 1220c (176f - 2228f)
15 min. soak
cool down max. to 900c (1652f)
Hold 30 minutes
Shut off kiln
Colorants or additives to a 100 gram batch are measured in percent to the
100 gram batch.
Standard Substitutions in all tests IF called for in recipe:
Local Boron Frit is used for Frit 3134
Forshammer (a half and half Potash and Soda spar) is the only Feldspar used
Local Boron Frit is used for Gerstley Borate
All substitutions are done not by Mol. Wts., but gram for gram.
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