Lynn Dickey on wed 27 mar 02
I have been lurking for a while, but now I have a question. I am a =
special student in a college ceramics class. I wanted to try the =
Peterson glaze from page 69 of the January 2002 Ceramics Monthly. I did =
tests of 300 grams and they all turned out good. Now I have made =
batches of 10,000 gms, of the 1st and 2nd red and they won't stay in =
suspension, just go to the bottom. I have added 1% bentonite, still =
goes to the bottom. I have added 1 tsp. epsom salt. It's some better, =
but still goes to the bottom. Do I need to add more bentonite or epsom =
salt or what?
Lynn Dickey
Cindy Strnad on wed 27 mar 02
Dear Lynn,
This sounds like a glaze which contains little or no clay. If this is the case,
bentonite won't help. If the Epsom Salts isn't doing the job, you can try CMC or
one of the other organics you'll find listed in your ceramics catalogs. These
will cause the glaze batch to sour and smell bad, but they don't affect the
finished product, as they'll burn out. I don't like the feel these ingredients
give to a glaze, but they may be your best bet. You can also just keep stirring
up your glaze. Don't leave it sitting for too long a period, or it'll form a
hard, solid lump at the bottom of the bucket which isn't usually worth the
trouble to fix. To avoid this, I don't bother with glazes that contain less than
5 or 10% clay. If you want the particular glaze for its special effects, then
you have to be prepared to put up with its personality quirks.
Good luck :)
Cindy
=====================================
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
cindy@earthen-vessels-pottery.com
http://www.earthen-vessels-pottery.com
CM Critique discussion forum
http://www.earthen-vessels-pottery.com/toforum.html
John Hesselberth on wed 27 mar 02
on 3/27/02 11:01 AM, Lynn Dickey at ldickey@THEI.NET wrote:
> I have been lurking for a while, but now I have a question. I am a special
> student in a college ceramics class. I wanted to try the Peterson glaze from
> page 69 of the January 2002 Ceramics Monthly. I did tests of 300 grams and
> they all turned out good. Now I have made batches of 10,000 gms, of the 1st
> and 2nd red and they won't stay in suspension, just go to the bottom. I have
> added 1% bentonite, still goes to the bottom. I have added 1 tsp. epsom salt.
> It's some better, but still goes to the bottom. Do I need to add more
> bentonite or epsom salt or what?
> Lynn Dickey
Hi Lynn,
Neither of these glazes contain ANY clay. They also have lots of neph sy and
frit which are notorious for hardpanning. They are going to be an ongoing
problem for you. Epsom salts won't do much of anything without any clay in
the system. Best thing I could suggest is to go to 2-3% bentonite. Make
sure you get it wetted well before you add it to an existing glaze slurry as
bentonite tends to just ball up and not mix if you are just dumping it in
dry. Good luck--these are just not formulated to be easy to work with. I'd
have to like them a lot to want to mess with them. If you want good
suspension properties in glazes look for ones that have 10% or more clay in
them.
John
web sites: http://www.masteringglazes.com and http://www.frogpondpottery.com
EMail: john@frogpondpottery.com
"Pots, like other forms of art, are human expressions: pleasure, pain or
indifference before them depends upon their natures, and their natures are
inevitably projections of the minds of their creators." Bernard Leach, A
Potter's Book.
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