Dai Scott on sat 18 apr 98
Help!!! While I have experienced a few glazes that, if left sitting for
long periods of time, were very hard on the bottom, I now have a glaze that
settles immediately after you stop stirring. When left overnight, I have to
do the drill-with-paint-stirrer thing---absolutely cannot stir it up by
hand! This is really a pain in the butt, but the glaze is an exciting one
to use, so I hate to give it up. I've tried bentonite (which everyone said
would help), Epsom salts (which everyone said would help), and CMC gum
(ditto), all to no avail. The glaze recipe is below---
Kona F-4 feldspar 53.00
Silica 20.00
Whiting 15.00
Barium Carb 6.00
EPK 6.00
This has an addition of 11% Mason stains.
I have never used stains to colour a glaze before ('way too expensive!), and
wonder if the stains could be the reason for the hard settling? Also, the
unfired surface of this glaze is extremely soft and powdery, very easily
"fingerprinted"; I thought the CMC gum would at least eliminate this, but it
didn't.
I'm getting kind of cranky about all this arm-breaking stirring. Any
suggestions??
Dai Scott - Pottery by Dai
in beautiful Kelowna, British Columbia, Canada, where the damn Canada geese
live all year 'round.
Tony Hansen on mon 20 apr 98
> Help...have a glaze that settles immediately after you stop stirring.
> When left overnight, I have to do the drill-with-paint-stirrer...
> tried bentonite, Epsom salts, and CMC gum...all to no avail
> Kona F-4 feldspar 53.00
> Silica 20.00
> Whiting 15.00
> Barium Carb 6.00
> EPK 6.00
> unfired surface of this glaze is extremely soft and powdeRY
Glazes are like clay bodies, they need lots of clay content to
have dry strength and good working properties (stay suspended,
apply nicely). This recipe has almost no clay.
Several ways to deal with this. Switch from EPK to ball clay. Ball clay
is much more plastic, but 6% is not really enough either.
Do some calculation to source Na2O/K2O from something else besides
Konaspar. When you reduce the konaspar you'll be able to increase the
kaolin to source the Al2O3 and SiO2 needed.
This glaze must have a very high thermal expansion? Crazing?
--
T o n y H a n s e n thansen@digitalfire.com
Don't fight the glaze dragon alone
INSIGHT, Magic of Fire at http://digitalfire.com
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