Marbles





Background

Marbles are small, round, spherical objects made from glass or stone and most commonly used in children's games. They are usually less than an inch (2.54 cm) in diameter and often brightly colored or otherwise decorated. Their origins as recreational objects appear to date back several thousand years, and it is also believed that the primitive games played with marbles eventually evolved into the sports that we now know as bowling, billiards, and pinball. Marbles have numerous industrial uses as well—they are the noise inside a can of spray paint and the translucent letters and numbers on a road sign. Marbles are also melted down to make fiberglass, used in automotive bodies and draperies.

History

Small, round objects made from stone have been unearthed in the excavations of ancient cultures all around the globe. The antecedent of the marble was probably the nut, polished by youngsters in ancient times into a smooth surface for playing games. Both Greek and Roman youths played games with small balls made from clay, and marbles were discovered in the tomb of the young Egyptian pharaoh Tutankhamen. In North America, objects of stone and clay that appear to be marbles have been unearthed from several sites. One of the most famous is the Hopewell burial sites in Ohio. Marbles and marble games for children continued to be a popular form of entertainment well through the Middle Ages. Unfortunately, youngsters playing marble games came to be seen as delinquents, and efforts were made to restrict their marble-playing activities.

Most of the marbles used in medieval and Elizabethan times were made from clay. Around 1600, water-powered stone mills in Germany began producing more polished versions from the marble and alabaster quarries nearby, especially in the regions near Coburg and Oberstein. The word marble is derived from the German term "for the rock," and has come to mean any small, round sphere used as such. Soon the mills began grinding out versions from agate, limestone, brass, and gemstone, and these large operations could grind a marble into shape at the rate of about 800 an hour. This made Germany the center of marble manufacturing for several centuries.

Glass marbles, the most common version of the object today, only came into existence relatively recently in the history of the object. It is debated whether they originated in Venice, where glassblowing had become a well-developed industry since the ninth century, or back in Germany. Historians point to 1846 as the invention of marbelschere (marble scissors) by a glass factory employee in Germany. This tool resembled a pair of tongs with a small cup on one end and a slicing device on the other. A molten glass rod would be forcefully inserted into the cup, and the worker would then twist the cup, which would help form the sphere of the marble. Squeezing the tongs shut sliced off the rest of the glass. Such marbles can be identified by their pontil marks, the two tiny tags at each end of the sphere where the cooling glass was severed from the rest of the rod. The objects were further cooled inside a wooden barrel and then taken up with an iron spoon and inserted into an annealing oven, a process which yielded a tougher piece of

Marbles
process which yielded a tougher piece of glass not likely to break or become brittle.

Marble manufacturing migrated to American shores in the later decades of the 19th century. In 1900 Martin Frederick Christensen received a patent for a machine that made near-perfect spheres of steel ball bearings. The first machine-made marbles were manufactured in a barn behind Christensen's house in Ohio, which eventually led to a prosperous manufacturing facility. By 1910 the 33 workers at the M.F. Christensen and Son plant were producing 10,000 marbles a day. The furnaces were fired by natural gas, however, and the onset of World War I brought rationing of the resource and spelled the fiscal end of Christensen's operation.

Akro Agate Company, founded in 1911 and originally based in Akron, Ohio, became the next major marble manufacturer. Further refinements in marble-making machinery came during the 1920s, and Akro Agate enjoyed a position as the major marble manufacturer during the subsequent decades. But the popularity of marbles as toys waned as more sophisticated gadgets entered the children's toy market. Many of the American marble manufacturing firms countered this by diversifying operations into industrial glass production, such as making automobile windshields.

Today, marbles are still produced in record numbers, but most are made in Third World factories. One such operation, Vacor de Mexico, located in Guadalajara, produces about 12 million marbles a day, which are then shipped to 35 different countries.

Raw Materials

Modern marbles are made from a combination of sand, soda lime, silica, and several other ingredients added for pigment or decoration. These other additives range from aluminum hydrate to zinc oxide. The primary component, sand, is essentially loose, granular particles of disintegrated rock. Soda lime is the chemical term for the mixture of calcium hydroxide and sodium or potassium hydroxide. It is a drying agent and absorbs carbon dioxide. Another compound used in marble manufacturing is silica, a white or colorless crystalline found in agate, flint, quartz, and other rocks. Some marbles are also made from cullet, or scrap glass.

The Manufacturing
Process

Meltdown

  • 1 Sand, soda lime, and crushed cullet are fed into a large, furnace-driven tank. In the tank, the mixture is heated to 2300°F (1260°C) to melt the raw materials. This can take as long as 28 hours.

Injection

  • 2 Next, the molten mixture moves out of the tank through an opening into another vat known as the flow tank. There an opening in the tank injects molten colored glass. This hot, pigmented glass gives the marbles their distinct appearance. A green marble has been injected with glass containing iron oxide; cobalt results in a blue marble; and manganese will yield a purple one. The use of uranium oxide gives marbles an eerie, greenish-yellow cast. The speed and force of the injection determines the final design of the marble. A grooved feeder device, patented by the Akro Agate Company, was able to produce multicolored marbles known as corkscrews.

Cutting and cooling

  • 3 Next, the still-molten glass is released from the flow tank as globs of glass. Automatic cutting devices slice the mixture into equal parts. The globs travel down metal ramps that simultaneously cool them and perfect their spherical shape. Next, they travel down a second metal slide and are sorted by hand. These grooved rollers were the invention of Horace Hill, a former employee of Christensen and Son and later founder of Akro Agate. This device produced marbles much more quickly and reduced the labor necessary by nearly two-thirds. Marbles with flaws are sent back to another area of the factory for re-melting. The marbles cool off in 5-gallon (19 1) containers that house 5,000 marbles at a time.

Where To Learn More

Books

Barrett, Marilyn. Aggies, Immies, Shooters, and Swirls: The Magical World of Marbles. Bulfinch Press, 1994.

Ferretti, Fred. The Great American Marble Book. Workman Publishing, 1973.

Periodicals

Block, Stanley A. "The Akro Agate Company." Antiques and Collecting, April 1988, pp. 38-40.

"Marbles: An American Industry Still Involved in a Shoot-Out." Compressed Air, July-August 1994, pp. 22-29.

Carol Brennan

User Contributions:

Richard
Report this comment as inappropriate
Jun 3, 2006 @ 4:04 am
Sand in glass manufacture usually refers to silica sand. So, your reference in the article to sand and silica is actually one and the same and a little misleading. One other main ingredient for glass manufacture which you have missed out is feldspar. Hope this helps clarify.

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