Mixing Plaster

Over the years, Plaster of Paris was used to cast footwear and tire impressions. Today, however, dental stone is used to for casting. Dental stone is a form of gypsum, as is plaster of paris, but dental stone is much stronger and does not require reinforcement. The durability of dental stone also lends itself to cleaning without the loss of detail from the surface.

Casting a footwear or tire impression is important for several reasons. The cast is actual size. It also reproduces minute details in the outsole including the sides of the outsole on deeper impressions. The casts will also supplement your photograph as well as eliminating scale and focus problems associated with photography.

Materials needed to cast an impression are as follows:

2-3 pounds of dental stone

One gallon zip-lock bags

A large spoon or paint stirring stick

6-9 ounces of water per pound on dental stone

A form (for placing around the cast if necessary)

(Fig. 1)	(Fig. 2)
Mixing procedures Place the 2-3 pounds of dental stone in a gallon zip-lock bag. (Fig. 1,2,3) This is enough casting material for one cast.
(Fig. 3)	(Fig. 4)
Add ¾ of the water to the dental stone and mix it thoroughly. (Fig. 4,5) The mixture should have the consistency of pancake batter or a little thinner. (Fig. 6) Add more water if needed.
(Fig. 5)	(Fig. 6)