Dice have been used for various gaming activities for thousands of years. The most modern, cube-shaped dice, marked with between one and six dots on each side, originated in China around 600 B.C. and are believed to have been brought to Europe in the 14th century by Marco Polo. Initially made of bone or ivory, most dice today are made of plastic, although some dice also are made of wood and various metals. The plastic that is used to make dice must be strong, colorless but easily colored and resistant to heat. Most of today's dice are made with thermoset plastics (plastics that start out as resins) such as polymethyl methacrylate.
Up until the 20th century, plastic dice were made entirely by hand, but today most dice are mass-produced by machines. The critical design element is the mold, made of steel. The liquid plastic is injected into the mold and allowed to cool; the mold is then opened and the dice removed. Before the liquid plastic is injected, colorants are added. To make white dice, manufacturers use an inorganic material such as titanium dioxide. Various other filler materials also are added to the plastics to make them more durable, including UV protectors, fiberglass and solvents such as glycerol.
The Final Stages
After the dice have been removed from the mold, they are washed and dried. Then the holes are drilled in and the die is ready for painting. Manufacturers have to make sure that each drop of paint weighs exactly the same as the plastic that was removed from the hole. After painting, the dice are tested and measured to make sure all six sides are perfectly balanced. Only when the dice pass the tests are they ready for packaging.
Cube-shaped dice with six sides may be the most common, but there are exceptions. Polyhedral dice became popular in the 1950s and are still used in trading-card and role-playing games, although their origins date back to the ancient Romans, who used dice with as many as 20 sides. Eight-sided dice also are quite common, used for games such as Dungeons and Dragons.