Sharon Miranda on tue 11 mar 97
Below is a glaze by Pete Pinnell which I've been testing. I love this
glaze, but recently the tests of this glaze and the Fake ash (which
everyone is calling Sharon's Fake ash to my utter amusement, since I
originally got it from clayart) have been appearing with tiny bubbles, like
a skin rash or something. I know the glaze was not overfired - I did a
long firing, with a fire down cycle at the end and took both glazes to cone
6. My question is: could there be a problem with one of the glaze
ingredients - like the strontium? Bad batch maybe? or too much or too
little? Outside of using distilled water, I'm at a loss as to what to
change to make these glazes work.
Pete pinnell's weathered bronze green (this is one beautiful glaze)
lithium carb 1
strontium carb 20
neph sye 60
ball clay 10
flint 9
plus
titanium dioxide 5
copper carb 5
must fire to cone 6, oxidation
You have all seen the recipe for the fake ash - in common with the above
glaze are the strontium carb , ball clay, and lithium carb.
BOTH these glazes came out with the same defect, that is little patches of
tiny bubbles.
Any help here would be gratefully appreciated, Thanks!
Sharon
P.s. I fired these glazes on Laguna white stoneware
Kris Baum on wed 12 mar 97
Sharon-
I've been using the Pinnell Bronze Green for a while and love it. Do you
get the wonderful purple undertones with this glaze? At first I had a
similar problem with the little bubbles which, for me, turned out to be
associated with dipping the pot into the glaze. (I have no idea why this
is. They don't show up until after firing. It seems more logical that
they would be caused by outgassing of the clay body.) The bubbles were
eliminated when I brushed the glaze on the pot, so now I always brush
this glaze. This works on ^6 red and white sculpture clay (grogged). BTW,
I found the original recipe a little too matt so I upped the lith carb to
1.5%
As an aside, for the last 25 years, in various "contract" studios, I
always dipped my pots for glazing and had fine results. Now that I
finally have my own studio, I seem to have lost my touch for dipping, and
get much better results with brushing. I'm sure it relates to my glaze
mixing, and I'm working on getting the glazes the right viscosity (?) for
dipping. I'm trying to get one that works so I can use that hydrometer
trick!
--
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Kris Baum, Shubunkin Pottery,
mailto:shubunki@erols.com
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Sharon Miranda on thu 20 mar 97
Thank you all for the help with this glaze. Tom asked how fast I fired:
can't be precise since I am away from my studio and can't look it up, but I
have a Skutt 1027 with kilnmaster - I used the slowest firing and added a
cool down cycle. total was about 14 hours (pretty slow if you ask me),
probably about 250 F per hour for the 1st ramp, then slowing down to 108F
at the end, finally down to 80F and then the cool down.
I did find that the glaze bubbled in applying it and I had to work it
smooth - I dipped these pieces, but I would much rather paint them on,
since I have gotten used to that in using commercial glazes and I don't end
up being glazed myself that way. (Man, do I trash my studio when I
glaze...)
I am going to try with more lithium, with a different flint mesh
(325),painting it on instead of dipping
and maybe even with distilled water - I'll let you know, I gotta have this
glaze!
Kris - what is the hydrometer trick you mentioned?
Sharon
*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*
Sharon LaRocca-Miranda *
92 Morgan Street *
Oberlin, Ohio 44074 *
Sharon.Miranda@oberlin.edu *
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