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20 Aug 2005
This test was undertaken to examine the affect of substituting SrCO3 for BaCO3 in Woo Yellow, a cone 10 matte yellow glaze. The Woo Yellow glaze recipe was taken from that provided to the list by Vince Pitelka. I calulated a version using strontium carbonate to completely replace the barium carbonate. Both recipes are shown below.
Woo Yellow Woo Yellow (SrO)
Code Number: Code Number:
========================================= =========================================
F4 SPAR..................... 35.90 F4 SPAR..................... 38.52
BARIUM CARB................. 27.20 ZINC Oxide.................. 17.49
ZINC Oxide.................. 16.30 DOLOMITE.................... 13.95
DOLOMITE.................... 13.00 EPK......................... 8.58
EPK......................... 8.00 RED IRON OX................. 3.30
RED IRON OX................. 3.30 BENTONITE................... 2.20
BENTONITE................... 2.20 STRONT CARB................. 21.46
========= =========
105.90 105.50
BaO 0.25* 22.92 11.89 CaO 0.15* 5.56 7.29
CaO 0.15* 5.11 7.26 MgO 0.13* 3.26 5.95
MgO 0.12* 3.00 5.92 K2O 0.03* 2.09 1.63
K2O 0.03* 1.92 1.63 Na2O 0.07* 3.00 3.56
Na2O 0.07* 2.76 3.55 ZnO 0.37* 19.19 17.34
ZnO 0.36* 17.64 17.25 Fe2O3 0.04 3.85 1.77
Fe2O3 0.04 3.79 1.89 TiO2 0.00 0.03 0.03
TiO2 0.00 0.03 0.03 Al2O3 0.19 12.39 8.93
Al2O3 0.19 11.42 8.91 SiO2 0.88 34.08 41.77
SiO2 0.88 31.41 41.68 P2O5 0.00 0.01 0.01
P2O5 0.00 0.01 0.01 SrO 0.25* 16.53 11.73
Below are the tests on Glacia porcelain. FC#15 and 16 are the original Woo Yellow, while FC#17 and 18 are my strontium carbonate version. FC#15 and 17 are fired in oxidation, FC#16 and 18 in reduction.
Below are the tests on Soldate 60 stoneware. FC#19 and 20 are the original Woo Yellow, while FC#21 and 22 are my strontium carbonate version. FC#19 and 21 are fired in oxidation, FC#20 and 22 in reduction.
The substitution while not perfect is pretty good. Examining the porcelain tests, one notes that the reduction test shows a very slightly more orange colour with SrCO3. The feel is also more satiny with the barium carbonate than with the strontium carbonate. Perhaps a little less strontium is required than barium, to achieve the same result.
The oxidation tests mainly show that the result is very similar for both glazes. I prefer the reduction colour on the porcelain, and one can see that the reduction on the stoneware really darkens the glaze, particularly where it is thin.