Accelerated Drying of Plaster Casts with a Microwave Oven

Calcined gypsum (calcium sul­ phate hemihydrate, CaS04 1/2H20), commonly known as plas­ ter of Paris, is used extensively in forming casts to immobilize parts of the body and for making molds used in the manufacture of orthotic and prosthetic devices. Plaster models and casts have several advantages, and a few disadvantages. Widely available, plaster is inert, sufficiently stable dimensionally, for the use at hand, and is inexpensive. Its major disadvantage involves the time required for it to dry sufficiently so that it may be modified and used for forming orthoses and prostheses. During its manufacture, plaster is prepared for use by reducing it to its powdery state. When it is used, it is mixed with water in approximately the proportions of two parts plaster to one part water. Plaster bandages are crinoline fabric strips in various widths and convenient lengths, rolled in the plaster to fill the interstices of the fabric with the powder. These are packaged and ready for dipping or wetting in water followed by application to the body or limb.