The first step in making a sculpture of your fingerprint is to enlarge it to an easily readable size. The space between the ridges is then replicated in rope, which is spliced at the intersections. Once the rope version is completed, it is repeatedly dipped in paraffin wax until it achieves the desired thickness (5/16" - 3/8" or 8 - 10 mm). This is the completed pattern.

A two-part mold is made by pounding sand mixed with clay and water tightly around the pattern. Gates, runners and a sprue are cut into the sand/clay mixture to allow the molten metal to flow into the mold. Vents are cut into the mold to allow gases to escape as the metal runs in. After the molten metal is poured into the mold and allowed to cool, the sand/clay mixture is broken away. The gates, runners, vents and sprue are cut off the metal fingerprint and the resulting fingerprint is polished using successively finer abrasives.

More general information about sand casting is available at: http://www.efunda.com/processes/metal_processing/sand_casting_intro.cfm