Dave Finkelnburg on wed 6 feb 02
You're on the right track. Just don't make this any more complicated
than it is. :-)
Let's say your glaze is 40 grams feldspar, 30 grams silica, 20 grams
whiting, and 10 grams clay, which adds up to 100 grams.
If you want to try 10% red iron oxide, add 10 grams of it.
If you want to try 1% Epsom salts, add 1 gram of that.
If you want to test 1.5% cobalt carbonate, add 1.5 grams of that.
You could do it the other way, too, but this is a lot simpler!
From: Jeremy McLeod
>My question has to do with the common percentage method of notating
>glaze formulas. The other-than-colorant ingredients add up to 100% and
>then the colorants are also expressed in percentages. Colorants are added
>as though they were part of the 100%? or in quantities that make the
>aggregate "add up to more than 100%?? Help??
Jeremy McLeod on wed 6 feb 02
Math challenged and newbie to glaze recipes... whadda combination!
My question has to do with the common percentage method of notating
glaze formulas. The other-than-colorant ingredients add up to 100% and
then the colorants are also expressed in percentages. Colorants are added
as though they were part of the 100%? or in quantities that make the
aggregate "add up to more than 100%?? Help??
So hypothetically... let's say the silica/flux/etc. part of the recipe is made up
of ten ingredients
in equal 10% portions. The colorant part of the recipe is one ingredient
and it calls for10% of it.
Do I add a measure of colorant equal to one of the 10% ingredients in the glaze?
Do I add an amount that would be 10% of the total glaze mixture?
My head hurts.
Cindy Strnad on thu 7 feb 02
You're making this too hard. Usually, the glaze
ingredients (sans coloring oxides, opacifiers, and
sometimes additives for better application such as
bentonite) add up to 100%. If they don't, that's
grounds for questioning the person who gave you
the glaze as there may (or may not) be a typo.
That extra stuff (mentioned above) that doesn't
fit into the 100% is just that--extra. You have
100% glaze stuff, plus 2% cobalt oxide, then the
grand total is 102%. We do this (I think) so we
can mess around with the glaze ingredients without
affecting the percentage of colorants, etc., or so
we can play around with colorants, etc. without
affecting the basic recipe.
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730