Ellen Baker on sun 9 mar 97
Some folks will tell you that differences in water quality are so
insignificant that you shouldn't waste your time worrying about it. It may
not significantly affect ratio:fit, but an experience we had with a color
change may be interest you.
Our water district changed to a new well about a year ago -- at the same
location, but drawing on a much deeper water table. The water quality
report was very good, and we didn't anticipate any change in our glazes.
Wrongo.
It just happened that we were due to re-mix a number of known "house glaze"
recipes shortly after the well change. We were surprised to see a
significant increase in "flecks" in a couple of our waxy ^10 glazes --
specifically a cream and a turquoise. These were little dark flecks, not
big iron spots -- and they appeared on white and red clay bodies, alike.
We keep a large supply of chemicals on hand, and were drawing from the same
lots. Therefore, we suspected the water. We mixed 10,000 gram test
batches with distilled water, and fired the glazes on the same clay bodies
in the same kiln for good science. The glazes came out basically
"fleck-free" -- with far fewer flecks than we'd seen with our old water. I
was really amazed at how much the water had affected the glazes' character.
Now we test all new glazes with distilled water. This is a totally
effective, scientific, and cheap "scientific control." If I think a glaze
could use a little "jazz," I'll try a small batch with local water, too.
If you have any nagging doubts or theories about how local water may be
affecting your glazes, I think it's well worth some objective testing with
distilled water. It's the only way you'll know for sure.
Best regards, Ellen Baker, Glacier, WA
orion@telcomplus.com
P.S. We asked for and got a copy of the official 40-pg. chemical analysis
of the water from the district. There are only trace amounts of iron,
manganese, copper, and a tiny-tiny-tiny amount of barium in the water -- I
mean really small amounts. I still can't believe how much difference these
made.
Jack Troy on mon 10 mar 97
Ellen Baker makes a good point about water being an important variable in
glazes. When I taught at Kent State one year I gave the students an
assignment that turned out to be quite revealing. We made up a good-sized
batch of glaze, dry-screened it several times, and everybody took about 100g
and mixed it with everything from distilled water to some from the Cuyahoga
River (which once caught on fire). Rain water, tap water, water from a variety
of lakes, streams and ponds were all used. The tests were fired on the same
clay in the same firing, and the results were well worth looking at.
Joseph Grebanier, in his book, _Chinese Stoneware Glazes_ mentions that New York
City tap water enabled him to get a copper red glaze that he couldn't achieve at
his summer home in Vermont. His testing showed that water was the only
significant variable.
Jack Troy
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