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Advice on mixing plaster from Bill Merril


From: Judy Decker (jdecker_at_TeacherArtExchange)
Date: Mon Aug 25 2003 - 18:49:17 PDT

Folks, Bill Merrill is on Art Education list.

Bill has some pointers on plaster mixing - and making a smooth wedging
board. I do like Marvin's suggestion to cover the wedging board with canvas.

(From Bill) Here are a few pointers about plaster for everyone..

So that you don't waste plaster figure how much plaster you need before
starting the project.
Use basic math...Example Height x Width x depth . 8" x 10" x 1" = 80 cubic
inches. For every 80 cubic inches of plaster needed you need 2 & 3/8 pounds
of plaster and 1 quart of cold water. I personally use about 2 3/4 to 3
pounds of plaster per quart of water to achieve a more dense mix. Measure
the amount of water (luke warm to cold) needed and slowly put the plaster
into the water. Do not stir! Wait 3 minutes or so before stirring. When
the plaster stands up slightly when dragging your finger across the mix
that's the time to pour. Keep testing the batch. Tap or vibrate the mix
before and after pouring. If you are making a wedging table use melamine or
Formica, and build a wooden frame to form the outside of the mold. If your
have mold release use it on the form, if not use a thin coating of Vaseline
or tincture of green soap. Make sure whatever you use that it only puts a
thin veil of resist on the mold. Make sure the sides and bottom are
securely attached to one another. Mix the plaster and pour into the mold at
that frosting cream consistency. Tap the mold sides and when the mix is
truly frosting like use a large straight edge or whatever you have to level
the plaster. After 15-20 minutes the plaster will become warm going through
chemical change to hardness. It's OK to loosen screws etc. whatever was
used to hold the mold together. Remove the mold later, turn the plaster
over and you will have a perfectly flat, ultra smooth wedging bat. There is
nothing better than plaster, one should let it dry out and scrap off the
wedging table with hard rubber ribs to clean it after wedging.

Use other math for cylinders etc. for amounts of plaster needed ...

Bill Merrill 360-417-6537

Bill are you from Washington Community and Technical College?

Judy Decker - Ohio
Incredible Art Department

P.S. I do like that I still remember the formula for finding volume of a
cylinder - thanks for the smile, Bill.