Gskwira@AOL.COM on mon 26 feb 01
I tried a new slip recipe recently, from the Rhodes/Hopper book, for Cone 1-6
damp clay:
Kaolin 25
Ball clay 25
Neph. sy 15
Talc 5
Flint 20
Zircopax 5
Borax 5
Despite a good ride in the blender, the slip had a lot of little lumps and
specks that made it go on less smoothly than I wanted. I've never used borax
before, but I know from my reading that it forms crystals. Is that the
culprit? Or did I not sufficiently dissolve it before mixing the slip? If
borax is the lump-producer, what would the result be if, say, I skipped the
borax and added maybe 2% of bentonite and a little cmc gum to help it go on
more smoothly?
Thanks for your thoughts.
/greg in michigan
Dennis Mummert on tue 27 feb 01
Greg - as usual, test, test, test. Mix up a small batch and fire it. The
borax is flux, so the slip won't fire the same as the recipe. To alter the
tendency to form crystals, (not inhibit completely tho), add several drops
of saturated sodium carbonate solution. Since this is a deflocculant, it's
presence shouldn't bother you much.
before, but I know from my reading that it forms crystals. Is that the
culprit? Or did I not sufficiently dissolve it before mixing the slip? If
borax is the lump-producer, what would the result be if, say, I skipped the
borax and added maybe 2% of bentonite and a little cmc gum to help it go on
more smoothly?
Thanks for your thoughts.
/greg in michigan
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Cindy Strnad on tue 27 feb 01
Hi, Greg
Mixing a slip/glaze up in the blender is a good first step. I haven't used
pure borax, so I couldn't say if that might be where your lumps are coming
from. Zircopax can also be a bit lumpy, though.
I screen all my glazes, even the tests. If you even strain it through a
kitchen strainer, that's a bit of a help. At least then you'll only have
very small lumps. It's just too difficult to see what the glaze looks like
with all those distracting nodules.
Another suggestion would be to wait until the next day to use the glaze and
at that point, mix it again. I use an immersion blender because it's
easier--no cleaning jars, pouring, etc.--but your container blender should
work as well. The thing is to give all those dry-on-the-inside lumps a
chance to soak up some moisture and soften.
If I remember right, using pure borax has some disadvantages. I think maybe
that would be solubility, but I can't remember for sure. Someone else may
comment on that.
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
earthenv@gwtc.net
http://www.earthenvesselssd.com
Wade Blocker on tue 27 feb 01
Dissolve the borax in very hot water before adding it to the glaze. Just
subtract the hot water used for dissolving borax from the amount of water
that you need in your glaze. Mia in overcast ABQ
Lili Krakowski on wed 28 feb 01
Whenever you can let the glaze steep in LOTS of water for 24 hours before
sieving. If the water is other than icy that should work.
Take a spoonful of borax dissolve in a glassful of warm water check next
day if it has dissolved. If it HAS (it should) dissolve your borax in
warm water, 24 hours early, add in disolved form.
If I remember correctly (Rhodes?) the borax is to harden the surface of
the dried slip (a kind oif crust.) If it makes you unhappy skip it. If
that affects the slip's maturity, add a little flux.
Lili Krakowski
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