Dice are implements used for generating random numbers in a variety of social and gambling games. Known since antiquity, dice have been called the oldest gaming instruments. They are typically cube-shaped and marked with one to six dots on each face. The most common method of dice manufacture involves injection molding of plastic followed by painting.
Dice have been used for gaming and divination purposes for thousands of years. Evidence found in Egyptian tombs has suggested that this civilization used them as early as 2000 B.C. Other data shows that primitive civilizations throughout the Americas also used dice. These dice were composed of ankle bones from various animals. Marked on four faces, they were likely used as magical devices that could predict the future. The ancient Greeks and Romans used dice made of bone and ivory. The dice of most of these early cultures were made in numerous shapes and sizes. The modern day cubical dice originated in China and have been dated back as early as 600 B.C. They were most likely introduced to Europe by Marco Polo during the fourteenth century.
Dice were typically handcrafted and produced on a small scale up until the twentieth century. As plastic technology emerged, methods for applying it to dice manufacture were developed. This allowed manufacturers to produce mass quantities of dice in a cost effective manner. Over the years a variety of patents for improved methods of dice manufacture have been granted.
The standard die is a six-sided, plastic cube. Each side is typically marked with one to six spots, or dots. These dots are arranged such that opposite sides always total seven. For example, the one dot side is opposite the six dot side and the three dot side is opposite the four dot side. In a two dice game, the dice are shaken and thrown on a surface. The rolled amount is indicated by the sides of the dice that are face up. If the dice are well-balanced and fair, each side has an equal chance of landing face up. Depending on the game, the player will either move her piece or collect money based on this rolled amount. Some popular gambling games that use dice include craps, chuck-a-luck, and poker dice. Board games such as backgammon, Monopoly, and Parcheesi also use dice.
Standard dice are available in a wide variety of sizes and colors. For board games a pair of 12 mm dice are typically used. These dice are considered imperfect because they have rounded corners, which reduce randomness. Since these dice are often used in children's games, they must be designed to meet certain toy safety standards. Casinos use perfect dice that may be hand made. They are generally larger than board game dice with a side measuring 33 mm. These are red, translucent dice which have precision-edges and corners and white dots. With this construction, rolls with these dice have the greatest probability of being fair.
Specialty dice are produced for many different applications. In some cases, the spots on a standard cube die are replaced by words, pictures, or symbols. Divining dice, which are used to predict future events, have different predictive messages on each face. Poker dice have card faces printed on each side. For blind people, Braille dice are available. Some games require dice that have a different number of sides and can provide a greater number of outcomes than standard dice. These polydice can have anywhere from three to 20 sides. They are used extensively in fantasy role playing games.
The key design element of dice manufacture is the mold. A mold is a cavity carved in steel that has the shape of the product that it forms. Typically, a mold is made up of two pieces which are forced together to form the cavity. When a plastic is injected into this mold, it takes on the mold's shape as it hardens. Since dice are solid cubes, using a standard mold is not practical because they would take too long to cool. For mass production of dice a special mold design is used. This mold is made up of separate chambers, which create individual elements of the die. As the individual pieces cool, they can be forced together to create a unified single object. The mold is then opened and the die is ejected. Special release agents are used to help make the plastic easier to remove from the mold. This mold design saves time because the smaller pieces can cool more rapidly.
Numerous materials have been forged into dice throughout history. This includes such things as bones, glass, wood, seeds, and metals. Today, the most widely used base material for dice manufacture is plastic. Plastics are high molecular weight polymers that are produced through a variety of chemical reactions. For a plastic to be suitable in dice manufacture it must have good impact strength, be easily colored, and heat stable. It is also desirable that it be clear, colorless, and transparent. Most dice are made with a thermoset plastic. One plastic that meets all of these requirements is polymethyl methacrylate (PMMA). Cellulose based plastics are also used.
Since the polymer, which makes up the bulk of the plastic is typically colorless, colorants are added to make the dice more appealing. These may be soluble dyes or comminuted pigments. To produce a white color, an inorganic material such as titanium dioxide may be used. Other inorganic materials such as iron oxides can be used to produce yellow, red, black, brown and tan dice. Organic dyes such as pyrazolone reds, quinacridone violet, and flavanthrone yellow may also be utilized.
A host of other filler materials are added to the plastics to produce a durable, high quality set of dice. To increase the workability and flexibility of the polymer, a plasticizer is included. Plasticizers are nonvolatile solvents and include things such as paraffinic oils or glycerol. To improve the overall properties of the plastic, reinforcement materials such as fiberglass are added. During production the plastic is typically heated. For this reason, stabilizers must be added to protect the plastic from breaking down. Unsaturated oils such as soybean oil may be used as heat stabilizers. Other protective materials that are added include ultraviolet (UV) protectors such as benzophenones to prevent UV degradation and antioxidants such as aliphatic thiols to alleviate environmental oxidation. Finally, compounds are also used during manufacture to aid in processing. This generally includes materials like ethoxylated fatty acids, silicones, or metal stearates, which help with the removal of the plastic from the mold.
The exact manufacturing process for any type of die depends on the base raw materials used. For mass production of imperfect standard dice an injection molding process is used followed by painting and packaging.
1 At the beginning of a dice manufacturing line, plastic pellets are
transformed into dice via injection molding. The pellets are plastic
beads that have all the colorants and fillers already added. They are
placed into a large bin known as a hopper and passed through a
hydraulically controlled screw. As they travel through the screw, they
are heated and melted. At the end of this screw is a spreader which
injects the molten material into a cool, closed two-piece mold.
- 2 The mold is made up of several chambers, which create multiple plastic parts. Inside the mold, the plastic is held under pressure and then allowed to cool. As it cools, the plastic pieces harden. The mold is then opened. When the mold is opened, the individual pieces are forced together to form a single solid cube. Because the mold was appropriately designed, this cube has indentations that will become the dots on each side. The cube is then ejected from the mold, coated and passed to the next phase of production via conveyor. Meanwhile, the two piece mold closes again making it ready to create the next die.
Painting and labeling
- 3 To complete the production of the die, they may be washed and dried before the final decorations are applied. First, the spots are appropriately painted. For specialty dice, words may be printed or images may be applied to each side. Company logos or other advertising may also be applied. These can be stickers or coatings. The coatings used during this step are specially formulated to adhere to the plastic and dry quickly.
- 4 Depending on the final use of the dice, they may be bulk packaged for use in board games, or individually wrapped for consumer sale. For board games, the dice are packed up into boxes and shipped to game manufacturers just like any other component material. When they are sold directly to consumers, dice are typically put into plastic blister packs with a cardboard backing. This package has the dual purpose of protecting the dice during shipping and advertising the product. The finished dice are then placed in cases and shipped by truck to distributors.
To ensure that each die produced meets specified quality standards, a number of quality control measures are taken. Prior to manufacturing, certain physical and chemical properties of the incoming plastic raw materials are checked. This includes things such as molecular weight determinations, chemical composition studies, and visual inspection of the appearance. More rigorous testing may also be done. For example, stress-strain testing can be performed to determine the strength of the plastic. Impact tests help determine the toughness of the plastic. During manufacture, line inspectors are stationed at various points on the production line. Here, they visually check the plastic parts to make sure they are shaped, sized and colored correctly. They also check the integrity of the final packaging. If any defective dice are found, they are removed from the production line and set aside for reforming. Computers are also used to control plastic use, mold retention time, and line speed.
In the future, dice manufacturers will concentrate on increasing sales and improving the production process. To increase sales, dice marketers will be involved in developing new games that utilize different types of dice. These games will require new types of dice that may have different shapes, sizes, and plastic compositions. From a production standpoint, future improvements will focus on increasing manufacturing speeds, minimizing chemical waste, and reducing overall costs.
Where to Learn More
Beasley, John. The Mathematics of Games. Oxford: Oxford University Press, 1990.
Chabot, J. The Development of Plastics Processing Machinery and Methods. Brookfield, IL: Society of Plastics Engineers, 1992.
Scarne, John. Scarne on Dice. Wilshire Book Co., 1992.
Seymour, R. and C. Carraher. Polymer Chemistry. New York: Marcel Dekker, Inc., 1992.
Chabot, J. and R. Malloy. "A History of Thermoplastics Injection Molding. Part I: The Birth of an Industry." Journal of Injection Molding Technology (March 1997).
U.S. Patent #4,012,827, 1977.
— Perry Romanowski