Casting Three-Dimensional Footwear Impressions
The popularity of casting footwear impressions has varied greatly over the years and it has depended upon the quality of photography at a given time. Early on, photography was rather crude with uneven lighting and low-resolution film. This resulted in photographs that often did not show sufficient detail for comparison purposes. Thus, casting was heavily used. At that time, the major method for casting was to use plaster of Paris. This is a dense material and sometimes several pounds were required for each cast. In addition, plaster of Paris is relatively slow in drying and when dry, is not very hard. Thus, when impressions were taken in dirt, the cast was often damaged during the cleaning process to remove the dirt. Figure 1 is a plaster cast of a shoeprint. In recent years, photography has improved greatly. New types of lights and lighting techniques have been developed. Higher resolution films have been introduced that show more impression detail. This has had the effect of decreasing the use of casting of impressions.
FIGURE 1 A plaster cast of a shoeprint.
At present, even with the development of digital photography and video, casting has made somewhat of a comeback. This is due to improved casting materials such as dental stone, which is less dense, dries faster, and shows more detail than plaster of Paris. Experts recognize several advantages of modern casts over photography. For example, even the best photography requires a level, two-dimensional subject to be most effective. If an impression is imbedded deeply into a substrate such as sand, it will be difficult to gain a proper perspective photographically. It will also be dif ficult to properly locate a measuring device and to even get a proper measurement of the size of the shoe that made the impression. In addition, if oblique lighting is used to photograph the impression, some of the most important details may be partially obscured in shadow. None of these are problems with a properly made cast.
