A print found in moist, firm, earth can be reproduced with little difficulty, however, when prints are found in sand or loose soil, it is advisable to spray them lightly with a fast drying shellac. The shellac will make the impression firm enough to withstand the plaster when it is poured.
In SNOW, a very thin, insulating layer of talcum powder over the print will aid in making the cast. The talcum powder will tend to insulate the heat produced by the hardening plaster and retard the melting snow.
PLASTER OF PARIS has by practice been the most practical medium for making three-dimensional footprint reproductions for evidence purposes. Plaster of Paris is inexpensive and easily obtainable at local hardware, art, hobby, or drug stores. However, when the finest grade of art or dental plaster is used, the resulting cast will be non-flaking and provide very minute details in an impression.