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making true underglazes with mason stains

updated tue 11 oct 05


Vince Pitelka on mon 10 oct 05

I had this information my office, so I couldn't send it until today. If =
you want to make a real underglaze that will brush smoothly onto dry =
greenware or bisqueware, the following is the formula that Mason =
Colorworks has been recommending for use with their Mason stains for =
twenty or thirty years. We have used it, and it works well. In the =
first section Mason didn't specify whether the measurement is by parts =
or by weight, so we did it by weight. In the second section they =
specify to measure by parts.

Mason Color Works Underglaze Formula=20
Components in Underglaze Base:
F-4 Soda Spar -------------------- 20=20
Kaolin -------------------------------- 10
Ball Clay ------------------------------ 5
3124 Frit -----------------------------10
Zircopax ------------------------------- 5
Underglaze Liquid ---------------- 75

Stain ---------------------------------- 40
(Or for a lighter tint use a mixture of stain and opacifier [Zircopax] =
to total 40)

Components in Underglaze Liquid
Propylene Glycol Anti-freeze --- 10 parts by volume
Water ---------------------------------- 10 parts
CMC Liquid --------------------------- 5 parts (To make CMC liquid, stir =
30 grams dry CMC in 1 qt. hot water and let sit for 2 days to break =

Note #1: Normal antifreeze is ethylene-glycol and is toxic. Propylene =
glycol anti-freeze is non-toxic, is sold in most auto-supply stores, and =
is much more friendly to the environment and to people and pets. =20

Note #2: The above underglaze mixture will allow you to brush-paint =
directly on dry greenware or bisqueware without your brush dragging.
Note #3: The presence of CMC gum will give a tough surface that is =
slightly more impervious to water, and thus glazes will not apply as =
thickly over underglaze. =20

Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111,