Stuart Altmann on wed 5 jun 96
Okay, I had this very large bowl--stoneware, glazed opaque semi matte white
with Rhodes 32, electric-fired to cone 9-10--on which I wanted to do some
lettering with acrylic paint, to provide a sign for my fair booth. Also
had a large platter--same glaze--that I was going to chuck out, but first
used to practice lettering. (Hint: works better if acrylic is diluted
slightly with water, not used straight out of tube.)
After I had covered the platter with lettering but still wanted more
practice, I stuck it under the faucet and scrubbed off the dark blue
acrylic with a rough cloth. To my astonishment, the platter now had a
network of crackled glaze, all stained dark blue. Quite beautiful,
really. Wow! I had not realized that this glaze was crackled!
I tried the acrylic treatment on several other pieces with the same glaze,
on none of which a crackle could be seen with the naked eye. Same result. I
then tried it on a different matte white glaze, also without visible
crackle: Toshiko semimatte white (from the Penland book), fired the same
way. Same effect: a network of dark blue crackle. Next I tried a
moderately glossy, beige glaze, 138 w/5% rutile (recipe posted previously on
CLAYART). Again, the acrylic revealed a crackled network, though with finer
lines/cracks.
What's going on here? Do all glazes have fine networks of cracks, or did I
by chance hit on three that did? Some other alternatives: (3) Maybe I
induce crackle by taking the pots out of the kiln while too hot. That's
possible, though my rule of thumb is that I don't open the ports and crack
open the lid until the kiln is below 175 C, and I don't remove pots until
100 C. (4) Maybe the acrylic or the scrubbing induced the crackle? I
don't believe it.
Meanwhile, what fun I'm going to have with this! Acrylics are waterproof as
soon as they are dry. They are available in hundreds of colors, so I'm
going to make me a 'Jacob's Pot,' with a coat of many colors. I won't use
the acrylics on things that are used for wet food or go into ovens, only on
decorative pieces. Does anyone know about the toxicity of acrylic itself or
the various materials used to color it?
Surely, someone else must already have discovered that acrylics will stain
glaze crackle, though I don't recall ever hearing or reading this. And how
strange to discover crackle networks in glazes that you never suspected of
having them!
Stuart Altmann
Valice Raffi on thu 6 jun 96
WOW! Thanks for your "accident" Stuart! I've used various colored inks
before, but this has inspired me. Plus, I believe that acrylics are more
impervious to changes with exposure to light.
I don't think that acrylics are non-toxic *at least none of mine say they are*.
Valice
Note: I used to think that I had lots of glazes without any crackle, but
looking at them closely, at an angle, shows the cracks. (I do have a
tendency to open the kiln early, however!)
Meg Schell on thu 6 jun 96
Toxicity(sp) can be obtained from the manufactuer of the acrylic, and I
think they can't be used for food containers because of leaching.
I have been using blue india ink to "bring out" the crackle pattern in
raku pieces, it works well and leaves cobalt blue spidery lines on the
work even after repeated scrubbing. I brush on the ink let it stand for
about ten mins then scrubb off. and Wow it really makes the crackle
patterns bright. I'll try acrylics, thanks for the idea
Meg Schell (in Brillantly hot and clear Orlando)
On Wed, 5 Jun 1996, Stuart Altmann wrote:
> After I had covered the platter with lettering but still wanted more
> practice, I stuck it under the faucet and scrubbed off the dark blue
> acrylic with a rough cloth. To my astonishment, the platter now had a
> network of crackled glaze, all stained dark blue. Quite beautiful,
> really. Wow! I had not realized that this glaze was crackled!
>
> Surely, someone else must already have discovered that acrylics will stain
> glaze crackle, though I don't recall ever hearing or reading this. And how
> strange to discover crackle networks in glazes that you never suspected of
> having them!
>
> Stuart Altmann
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