Paul Lewing on wed 13 dec 00
Well, Jewel, this is a classic boner! I sure am glad I've never done
anything that dumb! (yeah, right!)
But to answer your question, soda feldspar has, in addition to the
sodium, potassium, a little calcium (those are fluxes) and alumina and
silica (those are not). Soda ash has only sodium, which is one of the
most active flux oxides out there. So I would expect your "mistake"
batch to be much, mush glossier, if not downright runny. I would also
expect it to craze like mad, since sodium has a very high coefficient of
expansion, in fact the highest of any glaze oxide, while alumina and
silica have very low COE's.
If you have an accurate count of exactly how much feldspar and how much
soda ash are in there, you can duplicate the chemistry of the oringinal
glaze by adding clay and silica to what you've got. If you do have an
accurate count of what's in there, send me that and the original recipe,
and I'll tell you exactly what to add. However, the soda ash is also
soluble as the soda feldspar was not, so it may give you a whole range
of new problems for that reason, especially as it sits around.
But test it. It might be wonderful. And if you can't use it as is, try
blending in kaolin and silica in about equal parts to stiffen it back
up. Or line blend it with the stiffest stoniest matt glaze you have
around. That might be wonderful, too.
Good luck,
Paul Lewing, Seattle
Jewel Rubin on wed 13 dec 00
Hi all.
I have been lurking for a while with this group. I would like to ask a =
question that relates to a mistake I recently made.
I was mixing a batch of satin matt black glaze (school recipe) and after =
adding about half of the Soda feldspar that was called for in the glaze =
recipe, I inadvertently used Soda ash for the rest, approximately half. =
I realized the mistake after I had mixed the glaze and looked at the =
bag.
I went to my library to try to figure out what effect this would have on =
the glaze. I believe that the ash will make the glaze more alkaline and =
hence have likely will have less adherence to my pots. Does anyone have =
any ideas about what might happen with this glaze? I am fairly new at =
this glaze business, and have read everything I can get my hands on. =
I'm sure as time goes on and I continue to experiment more, I will gain =
a better understanding. =20
Any comments anyone has would be appreciated.
Jewel Rubin
Roswell, GA
Jewel@Rubin.net
Daniel Foscarini on wed 13 dec 00
You have found the great secret to great glazes, making mistakes. FIRE IT!
Also remember to write every detail down, nothing worse then finding a great
glaze and not being able to do it again.
Dan
P.S. ( you might want to try volcanic ash with black glazes, hint hint hint)
>From: Jewel Rubin
>Reply-To: Ceramic Arts Discussion List
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Soda Spar vs. Soda Ash
>Date: Wed, 13 Dec 2000 12:33:50 -0500
>
>Hi all.
>
>I have been lurking for a while with this group. I would like to ask a
>question that relates to a mistake I recently made.
>I was mixing a batch of satin matt black glaze (school recipe) and after
>adding about half of the Soda feldspar that was called for in the glaze
>recipe, I inadvertently used Soda ash for the rest, approximately half. I
>realized the mistake after I had mixed the glaze and looked at the bag.
>
>I went to my library to try to figure out what effect this would have on
>the glaze. I believe that the ash will make the glaze more alkaline and
>hence have likely will have less adherence to my pots. Does anyone have
>any ideas about what might happen with this glaze? I am fairly new at this
>glaze business, and have read everything I can get my hands on. I'm sure
>as time goes on and I continue to experiment more, I will gain a better
>understanding.
>
>Any comments anyone has would be appreciated.
>
>Jewel Rubin
>Roswell, GA
>Jewel@Rubin.net
>
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