Wade Blocker on thu 30 dec 99
Dear Tom,
This comes from David Greene's Handbook of pottery glazes.
The following are typical formulae unified on F203
Burnt umber
Mg0 0.11 Al203 0.18 Si02 0.89
Ca0 0.l8 Fe2 03 1.0 (H 2O 0.89) molecular
weight 284.96
Mn0 0.32
Raw umber
MgO 0.l6 Al203 0.09 Si02 0.69
CaO O.28 Fe2 03 1.0 ( H20 2.28 )
molecular weight 3l4.42
MnO 0.57
French Ochre
MgO 0.01 Al203 1.42 Si02 6.99
CaO 0.03 Fe203 1.0 ( H20 3.96 ) molecular
weight 8l3.81
Raw Sienna Al203 0.4 SiO2 1.18
Fe203 l.0 ( H20 l.98 )
molecular weight 307.43
Burnt Sienna Ca0 0.04 Al203 0.06 Si02 0.7
Fe203 1.0 (H20 0.61)
molecular weight 22l.23
I tested these colorants using Carlton Ball's recipe MG2 which I listed
recently.Fired to cone 8, oxidation.
100 grams MG2 plus l0 grams ochre gave a very nice dark brown
100 grams Mg2 plus 5 grams crocus martis = mat medium brown
MG2 over above = white with brown flecks
100 grams MG2 plus l0 %umber = lovely mottled brown.
Mia in sunny ABQ
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