Sandy Cryer on wed 18 dec 02
Response to: "I have decided to start mixing my own glazes (^6.) Just need to
know every detail for the newbie at mixing glazes "
Hi Tony,
Just don't confuse EPK with CMC. I figured 3 letters must be
close.......wrong!
I've learned a lot since those days. Pick a glaze with 3 or 4 ingredients.
Dry chemicals are usually weighed on a gram scale (invest in a good one plus
the scoop and a counter weight). Formulas are based on 100% which translates
into 100 grams. If the formula reads EPK 20% it means 20 grams, etc., this
can then be increased by multiplying each ingredient by the same #; if you
want a 1000gram batch (about 1qt +/-) then multiply each ingredient by 10.
The colorant and/or opacifiers & bentonite are often listed separately. They
are not included in the basic 100%, so the formula may have 112grams when you
add the 2% colorant (cobalt) and the 10% opacifier (zircopax) for example.
But these must also be multiplied by the #, so 1000 grams of the basic
formula would have 20 (10x2) grams of the colorant and 100 (10x10) grams of
the opacifier. So your total batch would weigh 1120 grams.
Be sure to wear a good mask & I recommend rubber gloves. I like to add the
dry to warm water as I weigh it out, keeps the dust down, start with a little
less water than you think you will ultimately need (maybe 2 cups for 1000
gm), more can be added when you sieve. Use a mixer attachment to the end of
a drill if you have one, or a big whisk works too, just takes more energy,
stir the mixture well. Then sieve 2 times, I use 50-80 mesh depending on the
glaze (some just won't go thru 80 or 100). I have a brush I got at the
dollar store, kinda long handled overgrown nail brush (prob. designed to
clean the toilet!), to help push the glaze slurry thru the sieve, paint
brushes work too, but I prefer the stiffer brush on the toilet cleaner!!
Just kinda "scrub" the screen as the glaze flows through it. Just a note
about bentonite and CMC, they tend to clump and get lumpy if added directly
to the water, you may want to dry mix them with the clay & slica in your
formula before adding to the water.
Hope all this helps. Email my off line if you have further questions.
Sandy Cryer in sunny AZ, heading for my second day of a fairly successful
craft fair (thankfully! both that it's been good AND that it is the last
day!)
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