Plaster is a strong and highly absorbent material with many uses. Common uses of plaster in ceramics include mold-making, bat production and creating surfaces for wedging and drying clay. Here at The Ceramic Shop, we carry a number of different types of plaster which vary in strength, set time, and application.
No. 1 Pottery Plaster is a great all-purpose plaster. It is commonly used for making slip molds and press molds. It is ideal for this purpose because of its fine particle size, which is great for capturing details. When mixing No. 1 Pottery Plaster, the consistency should be approximately 70 parts water to 100 parts plaster, and the set time is about 27 to 37 minutes. Compared to Hydrocal, Hydrostone and Ultracal, Pottery Plaster is weaker and more susceptible to wear; however, for mold-making, this plaster absorbs more water than the harder plasters, which makes it great for repeated back-to-back use in press molds.
Hydrocal is a plaster product that has a strength of compression twice that of No. 1 Pottery Plaster -- this just means that you will notice this plaster is more durable upon setting. Because of this feature, Hydrocal is a good plaster for making case molds and other larger molds. When mixing Hydrocal, the consistency should be approximately 45 parts water to 100 parts plaster, and the set time is about 25 - 35 minutes.
Hydrostone is a very strong plaster product, and is suitable when high-strength and wear resistance is necessary. For instance, Hydrostone is a great choice if you are making wedging surfaces for busy shared studio spaces. When mixing Hydrostone, the consistency should be approximately 32 parts water to 100 parts plaster, and the set time is about 17 - 20 minutes -- yes, this plaster sets a bit faster than many of our other offerings. Hydrostone is the strongest of the plasters we carry.
Ultracal is a low absorption gypsum cement that is made for close tolerance tooling, so if you are looking for a good material for jiggering/jollying, or working on a lathe, this is our recommendation. When mixing Ultracal, the consistency should be approximately 38 parts water to 100 parts plaster, and the set time is about 25 - 35 minutes.
FGR Plaster has a long set time, allowing for fabrication of strong, fiberglass-reinforced items. When mixing FGR, the consistency should be approximately 72 parts water to 100 parts plaster, and the set time is about 27 - 37 minutes.
If you are looking for a specific plaster material, and you do not see it on our product list, please give us a call at 215-427-9665 -- we will try our best to source it for you!