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raku crackle glazes

updated tue 13 feb 01


Susan McFarlin on sun 11 feb 01

I have been raku firing since last summer and find consistent=20
results with wh. crackle glazes to be impossible! initially, i used =
leaves and pine needles in a shallow pit directly on the ground. when =
winter descended, i switched to wood shavings as a combustible. Now, I'm =
thinking of trying to reduce in barrels, with newspaper. can someone =
take a look at my wh. crackle glaze and possibly suggest a better =
G200 FELSPAR.....320 thanks!
BARIUM CARBONATE.80 rick epstein

Paul Gerhold on mon 12 feb 01

Good crackle glaze results are a function of the difference in expansion
between glaze and clay so it is really not possible to recommend a glaze
unless you know the clay body. If you post your clay maybe someone using the
same body can help. If you are getting good crackle sometimes and not others
here are factors to consider.

1) Bisque temp. Recommend using large cones to monitor.
2) Thickness of the piece and thickness of the glaze (very imp.)
3) Firing temp of the glaze. At minimum use a pyrometer.
4) Amount of cooling before smoking. I think slower cooling makes bigger
5) Smoothing of the leather hard clay and definitely burnishing can change
crackle results.
6) This is just an opinion but I think moisture in the smoking /reduction
chamber can make a difference
At a minimum use metal garbage cans if possible and I recommend using dried
sawdust for smoking. I like to do a controlled rewetting of the sawdust
before smoking but I could just be kidding myself. Seems like a lot of things
I have been sure of in the past have changed with more experience.
Good Smoking
Paul getting ready for the Grove like a madman