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Manufacturing

Until the the 1900’s almost all marbles, especially those of glass, were made by hand. In 1846 a german glassblower invented glass scissors that were used to cut the still maluble glass into marble size pieces that were then formed into round spheres by hand. This slow and imperfect process made production of marbles very time consuming. This process continued until 1903 when Martin F. Christensen, being inspired by his patented machine for making steel ball bearings, made and patented the first glass marble making machine. 1 His machine utilized a pair of wheels with semi circular grooves that moved in opposite direction from their starting position in order to mold the glob of maluble glass into perfectly round spheres as they moved across the grooves and cooled.2 Various forms of this machine are used to make marbles in the present day. 3

Competition between companies

Although after time many of the different marble manufacturers began using similar manufacturing technologies, fierce compitition between them led companies to create intricate designs and patterns in their marbles in order to increase their demand. This was done by manufacturers creating their own glass “secret recipies.” There are various different techniques in creating a truly unique marble in color and pattern. The many different colors are the result of fluorspar, the usual basic sand, soda ash and feldspar that are the result of the making of the glass. To make the certain colors like white, blue, and the many other colors the use of zinc oxide, cobalt oxide and black copper oxide is used. When creating colors the temperature and the timing have to be just right. The fact that slight changes in temperature, timing, and other inputs going into the marbles led different manufacturers to have their own secret recipies in order to distiguish their marbles from others. The most important people involved in this process were the workers that worked in the factories. It was those workers that had the knowledge to tool the machine in accordance to a certain pattern. These men were the true artist of the marble machine era. The differences in recipies that were used between various maufacturers was so unique that to this day people are able to identify the manufacturer of an antique marble simply by looking at it. 3

Manufacturing Process

1.)Meltdown: 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. 2.)Injection: Next, the molten mixture moves out of the tank through an opening into another vat known as the flow tank. There is an opening in the tank that 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. 3.)Cutting and Cooling: Then 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 Martin F. Christensen and were then improved upon by Horrice Hill, a former employee of M. F. Christensen and Son Co. who later founded 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 containers that house 5,000 marbles at a time. 4

Marble Repair

Polishing and buffing are the most common methods used to repair marbles. "Cooking" is another way to repair marbles, but this method is much more difficult. Repaired marbles are sometimes passed off as fakes, so collectors need to be able to distinguish the difference between repaired and original marbles. 1.)Polishing and Buffing These two methods are used to repair surface damage to antique marbles. Polishing works the best in repairing handmade marbles. The basic method for polishing marbles is grinding and buffing the surface to make it smooth and delicate. Buffing is more suitable for machine made marbles. Buffing is able to fix simple cosmetic issues. If the marbles surface has been roughed, buffing will smooth the surface and make it shiny again. Chips and fractures caused from collisions cannot be repaired by buffing.

2.)“Cooking” “Cooking” is the most difficult method of marble repair, but is necessary in repairing chips and cracks. This repair method uses high temperature to melt fractured pieces of the marble back together. 5

Timeline of Marbles Manufacturers

 Category:Marbles