Autumn Downey on tue 27 apr 99
I have two iron type questions re: cone 6 oxidation.
1. I am wondering what causes red iron as an overglaze (red iron and ball
clay) to burn out. Is it simply that it's a weak colourant unless applied
very thickly? (Which would be too thickly to apply). It always looks
terribly red and interesting until fired. Then it's just a ghost of itself.
Or, is it to do with the glaze on which it is being fired?
2. I tried an experiment the other day in an attempt to get a brown terra
cotta looking underglaze/slip/engobe (whatever). Because clear glazes
usually look foggy over red clay, I thought the melting might improve by
mixing half red slip and half clear glaze and using this as an underglaze on
a white clay. As usual, it's ghostly.
Not foggy (I don't think), just faint, as though it has been eaten away or
burnt out.
Would a little tin or zircopax settle it down? Should I have added extra RIO
to the slip? Would black iron be stronger and produce better results?
Thanks for whatever light anyone can shed on this.
(Also, thanks to Tom Buck for the recent info on the different qualities of
red iron.)
Autumn Downey
downeya@internorth.com
Yellowknife, NWT, Canada
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