Extremely high heat needed to turn sand into glass

  • Workers at Kokomo Opalescent Glass create pendant lights by heating and shaping the molten glass mixture.

    Workers at Kokomo Opalescent Glass create pendant lights by heating and shaping the molten glass mixture. Courtesy of Kokomo Opalescent Glass

Updated 11/6/2012 3:18 PM

Students in Elise Diaz's fourth-grade class at Prairie Trails School in Gurnee asked, "Why does sand turn into glass if heated enough?"

On a beautiful fall day, the temperature rises to about 72 degrees Fahrenheit. The average human body temperature is 98.6 degrees Fahrenheit. Water boils at 212 degrees Fahrenheit.


Sand, when hot enough to make glass, must be heated in excess of 3,200 degrees Fahrenheit.

Tom Giles, vice president of Kokomo Opalescent Glass in Kokomo, Ind., explains how the process works.

"To get a furnace that hot to melt sand into glass will melt the furnace walls," Giles said. "If you add soda ash and an accelerant like potassium nitrate, the melting point for glass is 2,450 degrees, which won't melt the furnace."

Kokomo Opalescent Glass has been around since 1888. One of the company's first customers was Louis Comfort Tiffany, a world renowned artist who created decorative glass lamps, stained glass windows and colored-glass domes. Chicago has two remarkable examples of Tiffany's domes -- the world's largest at the Chicago Cultural Center on Randolph Street and another at Macy's on State Street.

Making glass takes nearly an entire day. Glass makers add chemicals to baby silica sand from Ottawa, Ill. The mixture is cooked in a furnace called a bee hive. The blend is stirred during the last four hours until completed, about a 20-hour process. A 700-pound batch yields about 600 pounds of glass.

by signing up you agree to our terms of service

Once the product is ready, workers scoop it into 50-pound ladles and quickly deposit the molten mass onto a steel mixing table. Colors are added and the entire mass is rolled into sheets that are cooled and made ready for shipping.

Giles says the process is complete when the mix looks like taffy.

"If it's not quite cooked enough, it can be left in the furnace for another 24 hours," he said.

Glassmaking has no waste; pieces cut from sheets can be remelted.

Kokomo's sheets of colored glass are sent worldwide to be used in religious buildings and as decorative elements in other buildings. They also manufacture a special glass blend that is strengthened with sand and resin, making it resistant to hurricanes and earthquakes.

The on-site Hot Glass art studio produces smaller glass pieces called rondels, bullesyes and dalles that artists use to create jewelry, stained glass, lighting and other artworks such as vases, paperweights and perfume bottles.

Tours and classes are available. Visit www.kog.com for more information.

Article Comments
Guidelines: Keep it civil and on topic; no profanity, vulgarity, slurs or personal attacks. People who harass others or joke about tragedies will be blocked. If a comment violates these standards or our terms of service, click the X in the upper right corner of the comment box. To find our more, read our FAQ.