JOAN AND DAN KINNEY on fri 3 sep 99
Hello,
Has anyone had any experience correcting a glaze from crawling? I use a
low temperature earthenware clay and glaze and mason stains under the
glaze for decoration.
The last firing had crawl marks on some pieces, always over the painted
stains. The two things that have changed are that I replaced the
elements in my electric kiln and I fired my bisque just a little hotter.
It's definitely not from dust or grease marks, which is what most of the
books say causes crawling. Any sugestions would be greatly appreciated.
Thanks very much, Joan.
Michael Banks on tue 7 sep 99
Yes, I've experience this one. The likely cause is your clear glaze is not
wetting the underlying stain because the stain mixture is too refractory.
It is possible that firing the bisc higher has resulted in less glaze
adhering to the pot, leading to less overlying fluxing power to "key" to the
stain substrate.
IMHO, The likely remedy is to add more frit or other suitable flux to the
stain to induce melting which allows co-fusion ("wetting") between glaze and
stain. I've found that certain stains nearly always require a flux to be
added to them. The worst offenders are the zirconium, alumina, chromium and
rare earth element (e.g.: praseodymium) bearing compounds, not surprisingly,
given the refractory nature of these elements.
Michael Banks,
Nelson,
New Zealand
>----------------------------Original message----------------------------
>Hello,
>
>Has anyone had any experience correcting a glaze from crawling? I use a
>low temperature earthenware clay and glaze and mason stains under the
>glaze for decoration.
>
>The last firing had crawl marks on some pieces, always over the painted
>stains. The two things that have changed are that I replaced the
>elements in my electric kiln and I fired my bisque just a little hotter.
>
>It's definitely not from dust or grease marks, which is what most of the
>books say causes crawling. Any sugestions would be greatly appreciated.
>Thanks very much, Joan.
>
Butch on wed 11 feb 04
We have a Camelion glaze that has been used very successfully for several
years. A new recipe has been mixed periodically as it gets low in the
bucket. The last batch was mixed Feb 2003. We add water periodically to
keep them from getting too thick.
Just recently they have started to crawl. This has always been a very
stable and reliable glaze. Not to mention popular. If anybody has any
suggestions on how me might save this glaze short of tossing it and
starting over.
Do any of the chemicals degrade over time? Any suggestions would be
welcome. Thanks.
The recipe is:
F4 Soda Feldspar 50
EPK 20
Talc 15
Whiting 10
Zinc Oxide 10
Lithium Carb 2
Copper Carb 5
This is a recipe I got from Mark Burleson's book The Ceramic Glaze
Handbook.
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