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glaze course lesson five pazrt two july 26

updated thu 27 jul 00


hal mc whinnie on wed 26 jul 00


Whatever happened to the silica?

Some Chinese glaze formulas for cone 10 reduction

If cone 10 Matt glazes have a large amount of kaolin as we saw in the first
part of this lesson, the oriental glaze has a high amount of both a feldspar
[flux or melted] and silica. They tend towards a high gloss because of the
silica and will flow well because of the lesser amount of alumna.

1] Oxblood/copper red

Neph syn 166
Custer spar 35
Kaolin 8
Flint 88
Colemanite 51[gertsley borate]
Whiting 41
Copper carb 4
Tin oxide 7

Note this glaze has to be well ground.

[Also the secret in these glazes is the way they are fired in reduction. I
have fired them with great results by adding sticks of wood to a gas kiln
during the last 2 or 3 cones and adding wood after temperature has been
achieved. This is best done by the addition of small sticks through a burner
port or in a spy hole or both.]

2] Oxblood semi Matt red
Cone 10 reduction

Custer spar 301
Colemanite 41
Whiting 45
Copper 4
Tin 8
To increase Matt surface
Add barium 38 and Epk 38


Look at the above formula, where is the silica and alumna which every glaze
has to have to be a glaze?

How could one compute a seger formula for this glaze?