Keiko Imaoka on wed 1 jan 97
hello and happy new year to everyone! (akemashite omedetou gozaimasu)
i've been on the list for about a month, and have enjoyed the informative,
lively discussions on pricing, consignment, toxicity, etc. while reading
the recent woodfiring thread, it occured to me that we could go a long way
towards protecting the environment if we could join forces to eliminate all
glaze wastes around our studios.
a couple of months ago, i started looking for ways to reclaim the glaze
scraps that come out of a university studio where i was taking a class. the
glaze sludge collects at the bottom of two huge buckets where we wash
glazing tools, and is periodically scooped out into 5 gal buckets to dry
outside, then hauled off to a toxic landfill. i wanted to eliminate the
toxic waste by using it to formulate some oxidation glazes to add to the
pallete.
the materials that go into the sludge consist of amaco underglazes, raku,
c04 (Satellite and majolica) and c3 glazes, colored slips, oxide stains, and
tera sigillata byproduct (all free of lead). i saved about 5 gallons of
sludge at two different times, sieved them through a 60 mesh screen, and
started my sludge glaze experiment.
the two samples (both about 57% water - fairly thin) turned out to be quite
different. at c3, sludge-I fired as dry as a stoneware slip, and sludge-II
matured to greenish black. the former probably contained a fair amount of
tera sig waste, and therefore low in silica, since adding (and increasing
the amount of) frits or fluxes didn't make it go glassy. i wanted to keep
the process simple, so instead of adding silica and fluxes, i decided to mix
it 50-50 (by volume) with raku and other c06 glazes to see what would happen.
to make just enough to cover a test tile, i mixed up 1/2 tsp each of
sludge-I and a glaze for each of nine raku glazes and fired them to c3. the
resulting glazes ranged from clear to translucent to black, of which i
selected the four most attractive ones for mixing in a larger quantity. i
followed the same procedure for sludge-II and fired to c04, which yielded
very similar results.
what i ended up with were two identical sets (c04 & c3) of glazes that have
the rich, muted appearance of high-fire reduction glazes (though they were
fired electric), particularly over red clay bodies. they were also easy to
brush because of colemanite in raku glazes. the most popular among students
was a greenish transparent glaze speckled with cobalt blue. some of the
glazes seemed more crazing-resistent than the regular glazes. a pair that
were made of sludge and red-luster raku looked so much like tenmoku over red
clay that i named them "sludge tenmoku." majolica base glaze also turned
out to be a good additive to the sludges, producing blue speckled medium gray.
i also mixed sludge-II half and half with each of c3 oxidation glazes used
at the studio, and fired them to c3. again, this gave the glazes the
pleasing appearance of reduction-fired glazes, and mixing the sludge with a
"mottled black brown" resulted in a semigloss pitch black. these were quite
attractive over a buff stoneware body (rods bud) as well.
the best part of all this was that other students were very supportive and
enthusiastic about the project and volunteered to use the sludge glazes on
their large and small pieces.
granted, the next batch of sludge will be different from the current ones,
and the recycling process will require ongoing testing. but things are not
as uncertain as they may seem. i can expect the sludge color to remain more
or less the same, since it's a mixture of everything used at the studio
(though the maturation temparature may vary depending on the amount of tera
sig waste), and the fresh glazes used in the process give it a measure of
consistency.
if you'd like to try this yourself, all you need are measuring spoons and
cups. no weighing is necessary. things will be different for each school,
so follow your instincts. though no glaze calculation is involved, it's
helpful to have some knowledge of glaze chemistry. if you work in your own
studio, and glaze-fire to one temparature, the matter will be much simpler.
i'm starting on a new research project at home, in trying to find ways to
recycle the tera sig byproduct; i.e., the coarse particles that settle to
the bottom. though the material is obviously not suited for making regular
clay, it should be useable for glazes and slips. i just mixed up a small
quantity of casting slip using ball clay waste. i'll let you know if this
works okay for casting and/or decorative use. but since i do virtually no
casting (and have no molds to speak of), it would be nice if a casting
person could look into the matter.
keiko imaoka
tucson, az
Louis Katz on thu 2 jan 97
You can recycle the sludge from Terra Sig recipes into your clay body by
washing. put a few gallons of sludge in a garbage can fill with water,
stir, let it settle, siphon or scoop off the water and wash it again. This
will remove the bulk of the remain deflocculant.
Louis
***************************************************
*Louis Katz lkatz@falcon.tamucc.edu *
*Texas A&M University Corpus Christi *
*6300 Ocean Drive, Art Department *
*Corpus Christi, Tx 78412 *
*Phone (512) 994-5987 *
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