Richard Aerni on sat 10 aug 96
Hello everyone,
Just back from a restorative vacation and seeing questions about chrome
pinks--I'm not sure I have anything of a definitive chemistry-oriented
nature to add, but I dabble in a lot of forms of chrome pinks in my glaze
work and have some "try it and see" type experiences to share.
I was trying to explore some of the oxide variations/combinations possible
with wood ash some years ago, and was messing around with chrome. Thinking
I'd be working in the green range, I was hugely surprised to start pulling
out multiple samples of pink runs, pink flashes, etc from the kiln.
Surprised because I was using no tin or opax in any of the glazes (being
familiar with the chrome/tin reaction in reduction fired stoneware, mostly
in its unattractive forms). After a number of firings and experimenting,
and pondering the results over coffee in the studio, I've come up with an
answer (for me) that works in my kiln. Perhaps someone with a more
theoretical/scientific bent will comment on this, either reinforcing or
debunking the whole mess.
I've concluded that the pink comes about from a chrome-rutile(titania)
reaction [unlike Sam Drew's conclusion] in a calcium based glaze [unlike
June Perry's observations]. My most reliable repeatable pink flash comes
about when a chrome and iron bearing slip is put down on the pot, then
covered by applications (sprayed, single-fired) of an ash glaze containing
up to 20% rutile (the kind of rutile matters a great deal, as I've learned
to my chagrin in the past year), then overlaid with my "typical" ash glaze.
These ash glazes have a very high calcium content. The flashing occurs in
zones where the relative concentrations of titania/chrome and calcium occur
in the optimum proportions, IMVHO, and I can't be more definitive, since my
way of working with glazes precludes anything resembling "control" in the
scientific sense. I fire my kiln in a clear oxidizing atmosphere up to
around cone 1, then put it into mild reduction through to the end, cone 10.
Lately I've been "firing it down" for a couple of hours at the end, and have
found that this softens the colors. When (I think) the kiln gets a bit too
much oxidation, the effect can be a brownish/pink "furry" look. Similar
pinks can be reliably produced by using a glaze found in one of Dick
Lehman's excellent articles in Ceramics Monthly of a few years ago--I think
it might have been entitled "Steal This Glaze", or something like that.
So that's my contribution to this discussion, for what it's worth. I'm
about to settle into a regular routine of potting again after spending what
seems like months getting ready for shows, doing them, and recovering from
them. Hello to everyone out there whom I've lost contact with during this
crazy summer (I'll be back in touch), to everyone from Clayart whom I met in
person "It was great to meet you (each and every one)--really!!" , and I
realize I've got a lot of catching up to do with the list (I haven't
forgotten I need to update on the joys and pitfalls of hiring help in the
studio--coming up in the next few weeks).
Take care,
Richard Aerni
Levine Meg Jessica on sun 11 aug 96
I have had pink flashing from the combination of a tin based white glaze
on the same form as one which was colored with Golden Ambrosia Mason
Stain. I was surprised when this golden glaze made the white glaze blush
to pink. The stain has ingredients including Chrome, Iron, Zinc and
Alumina. I think it probably is the the chrome and the tin which make the
pink. At times, I love the effect of that pink blush on the white glaze.
I really can't stand it though when combined with this gold glaze. Meg
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