Making Glass Marbles

What Are Marbles Used For?

The first marbles ever made were constructed by the Egyptians, out of fired clay. Since then, they've been made from carved stone, and finally from glass. It's interesting that, given how old marbles are, they've only ever been used for games and as a form of decoration. While steel ball bearings and other metal spheres have industrial uses, marbles made from glass are used in all sorts of children's games. Perhaps what makes them so popular is the variety of colors and ornamentation they display.

How Are Marbles Made Industrially?

Marbles are made on a large scale in factories, using a few pieces of machinery and lots of second-hand glass. A large furnace is loaded with glass, be it pieces of broken bottles or colored granules specifically made for this purpose. Once the furnace peaks at an internal temperature exceeding several thousand degrees Fahrenheit, a port is opened in the furnace's bottom. Molten glass flows out and down. An industrial set of shears powered by a pneumatic piston cuts the molten glass into thumb-sized globs. The globs pass down a hopper to be rolled for several gears, caught and carried by two over-sized worm screws. As the globs are carried, the rolling motion of the worm screws rolls them into perfect spheres. By the time they reach the end of the screws, the marbles are cool enough to retain their shape. Once they've returned to room temperature, they are packaged for shipping.

How Are Marbles Made Individually?

Marbles made by hand tend to be more colorful, as the glass colors used in the industrial process mix at random. However, a glassworker can pick the colors and patterns she will use. A lump of clear glass is set into a furnace. Once it is molten, it is retrieved at the end of a large metal rod and rolled around at the end so it sticks. It's rolled into a cylinder, and rods of colored glass are then inserted or embedded into its sides. The lump is then put back into the furnace until the colored rods mix. At this point, the lump is rolled back into a cylinder so more colors can be added, or it is twisted like taffy, using a set of metal tongs, until a sphere forms at the end. The sphere is cut free using a set of shears, and the process is repeated until there is no more usable glass at the end of the rod. Before the spheres can cool, they are rolled between two heat-resistant pads to ensure they are perfectly round and smooth. With this done, they simply need to cool down to be finished.

Resources

• Video on making marbles