Gypsum is a white powder that consists mainly of gypsum. It can be mixed with water to form a thick grout that can be used to cast in molds to reproduce objects or it can be used to make a mold that can reproduce finely detailed models.
A variety of gypsum plasters and cements are used in the making of molds, master models, and finished art forms. These products come from highly versatile raw material gypsum, more commonly known as “Plaster of Paris”.
Plasters used for the manufacture of molds:
– Ceramic plaster
-Ultracal
Plasters used for casting:
– Ceramic plaster
– Cast plaster
– Hydrocal
– Hydrostone
– GardenCast
– FGR-95
Plasters for the manufacture of molds
Ceramic plaster
This is a high-quality white plaster with the ability to absorb large amounts of moisture. This makes it ideal for use as a ceramic mold by absorbing water from the ceramic slip used in casting. This leaves a semi-dry reproduction of the shape of sufficient thickness to allow it to be removed from the mold for later baking in the oven, once the excess slip has been poured.
Ultracal 30
This is the most widely used gypsum cement with the lowest expansion rate available. It is ideal for casting epoxy and polyester resins, as well as being the industry standard for casting foam latex. It has a high resistance with less tendency to deform. It has a set time of 30 minutes. It has a dry compression of 6000psi.
Casting plasters
Casting plaster
This product is used for the economical production of figurines, etc. of rubber or plastic molds. It is ideal for young children in kindergarten and elementary schools as a craft and educational tool. It is widely used in the production of “white tableware” for use in plaster painting classes.
It is ideal for these activities as it has a hard surface that resists chipping and provides an excellent surface to decorate.
White hydrocal
This is a good general purpose product. Offers slightly better heat resistance along with increased wet and dry strength. It is ideal for making ceramic molds.
It is a neutral gypsum cement with a setting time of 25 minutes. It is commonly used for casting both hollow and solid lamp and statuette bases. It is very white in color.
Hydrocal 105
A good strong mold material. Commonly known as a “polished” stone due to its color. It is ideal for casting dentures and for dental stones with controlled expansion.
Hydrostone TB (USG)
Hydrostone is a gypsum cement especially indicated for jobs that require high strength and resistance to water absorption. It is used in high-quality novel art and sculpture pieces. Works well in latex, silicone, and polyurethane molds.
Garden cast
This gypsum cement can be used outdoors. Sets in 30 minutes and can be mixed with equal amounts of outdoor statue sand.
Alpha FGR 95 gypsum cement
FGR 95 is a unique high strength gypsum cement. It is safe and non-toxic with zero flame and smoke spread. It is designed for fiberglass reinforcement. It is used for intricate interior architectural elements.
This is used in Forton acrylic polymer modified gypsum formulations.
What is gypsum cement?
To give a general distinction between the two commonly used terms, gypsum and gypsum cement. Gypsum generally refers to a lower strength gypsum and gypsum cement is a higher quality variety of gypsum with special properties.
Gypsum cements generally have low moisture absorption, high compressive strength, and fire resistance. They are more expensive and extra care must be taken in mixing. In other words, they are harder and stronger than ordinary plaster.