Marcia Selsor on sat 7 apr 07
Dear Bruce,
I had to laugh because I just came in from my studio after mixing
plaster for a
sprigging mold of 8 shapes and a bird bath hump mold that will fit
into a suitcase for the Architectural
workshop in Cleveland.
I am basically low tech. Mainly because I have traveled a lot and
tried to do things
in foreign places where there is very little high tech available.
Mixing plaster- #1 Pottery Plaster (I use this primarily)
I learned from a European Plaster Mold maker: Petras Vaskys, my
professor from Phila. College of Art.
My proportions are close to what you are doing but I don't measure.
I eyeball what I think I'll need and put half that of warm water into
a mixing container. Warm water sets up faster.
Then I sprinkle cup (or scoop) of plaster slowly into the water.
I continue to do this until I have a substantial "island " of plaster
floating in the center of the bucket -probably half of the surface area
I let it slake for a few minutes
Then I stir is for 10-15 seconds or better and let it rest.
I tap the air bubbles to the surface
Then I spray diluted alcohol with water onto the air bubbles which
disolves them instantly (learned this from Richard Notkin)
I skim a finger across the surface until I see the ripple stay in place.
Then I pour.
I tap the table to get air bubbles to to top and spray again with the
alcohol solution.
Then I come into the house and read email or cook dinner. I'll check
the molds in the morning.
I have been mixing molds this way for over 40 years. I also assisted
Nick Vergette on the first 1% for
Art commission in 1971 for the Federal Building Reflection Pool in
Memphis. I was one
of the plaster technicians for the forms to be cast in Bronze. That
is one qualifying experience.
I'd be happy to answer any questions. I have never measured water to
plaster. I never felt I wanted to change the way I was taught.
Marcia Selsor
http://marciaselsor.com
Vince Pitelka on sun 8 apr 07
I always mix plaster with a drill impeller mixer, always using a
variable-speed drill. Keep the speed low and the mixer-head down deep in
the plaster and it won't suck in air at all.
After you finish mixing the plaster, gently pound the bottom of the bucket
against the floor for 30 seconds or so, and it will force any bubbles to the
top.
There's a good section on mixing plaster in my book, and the mixing ratios
were all provided by US Gypsum, so they are accurate.
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Bonnie Staffel on sun 8 apr 07
I also learned the same way as you, Marcia, in my first year hand building
class in 1948. I do not use a jiffy mixer but my hands to stir the plaster
after it slakes a few minutes. I then didn't get any or many air bubbles.
Same as for the rest of your description. We didn't know about the alcohol
spray back then. Sounds like a good idea.
Bonnie Staffel
http://webpages.charter.net/bstaffel/
http://vasefinder.com/bstaffelgallery1.html
DVD Throwing with Coils and Slabs
DVD Introduction to Wheel Work
Charter Member Potters Council
Marcia Selsor on sun 8 apr 07
Bonnie,
I didn't learn with a jiffy mixer either but I prefer it to mixing by
hand. i still manually check
for lumps. Fresh plaster is a must.]I thank Laura Freeman for her
gift as a winter Texan to
Brownsville for bringing me some fresh plaster straight from
Standard in Pittsburgh, Pa.
I'll get to se how long it lasts in humid Brownsville. My Montana
plaster lasted years in my pasement in plastic bags.
I am using my new texas studio. SO HAPPY!!
Marci
Marcia Selsor
http://marciaselsor.com
Russel Fouts on mon 9 apr 07
Marci,
>> I'll get to se how long it lasts in humid Brownsville. My Montana
plaster lasted years in my pasement in plastic bags. I am using my
new texas studio. SO HAPPY!! <<
HOORAYYYY for you!
From one humid country to another. To keep humidity out of plaster,
try saving all of those little drying packets they pack with camera
and other elecronics. Throw a bunch in the bag with the plaster and
double bag it. I don't know if it helps but it seems like it would.
Also, have you considered a dehumidifier in your studio. I know that
it's airconditioned. Would that keep the air dryer?
Russel
Russel Fouts
Mes Potes & Mes Pots
Brussels, Belgium
Tel: +32 2 223 02 75
Mobile: +32 476 55 38 75
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