Glossary
Plaster - gypsum, we use USG Pottery Plaster #1, it has a good balance of strength and porosity
Slip - deflocculated liquid clay, Darvan is used to thin the slip and keep the clay particles in suspension
Greenware - wet clay, before it is fired
Leather Hard - a state of dryness that is stable but still workable, a good time to attach pieces, the texture resembles leather
Bone Dry - a state of dryness when pieces are ready for bisque, they should be completely dry and not cool to the touch
Bisque - clay that has been fired to △06 or approximately 1828° Fahrenheit. This is when clay becomes ceramic and permanent, it is porous and ready to glaze.
Glaze - a glassy substance that is liquified during the firing, fired to △6 or approximately 2232 ° Fahrenheit.
△06 - approximately 1828° Fahrenheit
△6 - approximately 2232 ° Fahrenheit
Cottle Boards - adjustable boards that create a frame around your object, what the plaster is poured into
Flashing - flexible metal that can be used instead of cottle boards to make a cylindrical mold
Slake - full hydration, a 2 minute period before mixing where the plaster and water rest
Sprue - the funnel section of a two-part mold that is removed after casting
Key - notches made into the first part of a two-part mold before pouring the second half
Release - applied with a brush before pouring a mold, used to prevent sticking, Murphy’s Oil Soap
Undercut - a spot on an object that prevents the mold from releasing. Undercuts prevent a mold from being successfully made and cast.
Ceramic supply stores
Places to shop for your own materials, tools, and glazes.
Rovin Ceramics - Ann Arbor
Runyan Pottery Supply - Clio
Artists
Andy Martin Porcelain Casting Slip Recipe △6 - 2.5 gallons
(This recipe tends to run thick and I typically will add a little extra water.)
10 gallons of slip, or 4 buckets, will be provided during the class.
2.5 gallons is the maximum amount that can be mixed in a 5 gallon bucket due to the volume of the dry materials.
The class will start with one bucket of slip on Week 2 and more will be made as needed.
If you are ever in need more slip please send me a text at 860-726-3273 and I will make more as soon as possible.
Members
Once the class is over you will be in charge of supplying your own slip and plaster.
I can advise on where to buy slip or materials to mix your own.
Members do not have access to the glaze/slip mixing area in the studio.
If you want to mix your own slip you will have to contact a studio tech to assist with the mixing.
Slip casting with a one piece mold
One Part Mold Making
More on GlazE
We will have two glaze demonstrations during class.
One on April 26th (fifth class), and a refresher on May 3rd (sixth class).
Every glaze is made of the following 3 materials:
Silica – Creates glass. Examples: quartz, flint, pure silica
Alumina – Stiffens the glaze so it doesn’t slide off the clay. Examples: clay (kaolin, ball clay, or fire clay), alumina hydrate
Flux – Causes the glaze to melt at a low enough temperature to be used in ceramics. Examples: feldspar, whiting
Plus a glaze may include one or more additives:
Opacifiers – to make the glaze opaque instead of transparent. Examples: tin oxide, zirconium or Zircopax, titanium, zinc
Suspenders – to keep the glaze in suspension instead of settling out. Examples: bentonite
Colorants – to provide various colors. Examples: cobalt oxide, copper oxide
(Glaze ingredient descriptions from bigceramicstore.com)