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How to Melt Recycled Glass

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You can melt recycled glass, also known as "cullet", on its own or mix it with glass-making batch materials such as soda ash, limestone and sand to supplement a new mixture of glass. Mixing the "cullet" with batch materials improves the melting process and makes it more workable. You have the option of buying pre-crushed "cullet" from manufacturers that will save you the time and effort that is needed to crush the glass yourself, or from using a glass crushing system to crush your own "cullet".

Clean the recycled glass. Any dirt or materials in the "cullet" will influence the final outcome of the product.

Separate the different colors. Mixing different colors of "cullet" during the melting process can ruin the overall color of the resulting glass.

Separate the different types of glass as much as you can. You want to utilize the glass that has as few other additives, like metals, as possible to create a uniform mixture. A few discrepancies will not adversely affect the mixture, but a sample of "cullet" that is almost identical is the safest way to go.

Crush the recycled glass into "cullet". Use a glass crushing system, such as the "EME Wired Glass Crusher System", to crush the recycled into "cullet" that measures between "1/16" and "¾" inches. The crusher system also sifts the materials to remove any debris that was left behind.

Heat the furnace. It takes less energy to melt "cullet" than it does to melt typical glassmaking batch materials. The temperature depends on the "cullet" materials and added chemicals, but between "2250" and "2350" degrees Fahrenheit is the accepted range.

Add the "cullet" and batch materials to the furnace. There are different glass recipes to choose from in terms of what batch chemicals you should add to your "cullet". These chemicals range from a common batch material like soda ash, to borax and niter. The amount of glass that you add to the furnace at one time is called a charge, and it takes multiple charges to fill a furnace. Allow each charge to melt to a cottage cheese-like consistency before adding another.

Refine the glass. Refining the glass consists of removing the bubbles. To do this, turn down the temperature of the furnace between 50 and 100 degrees and allow the glass to sit anywhere from six hours to overnight to remove the bubbles. After you refine the glass, you can turn up the heat and begin working with the glass.


Melting the glass at too high a temperature can result in the development of scum.


Marissa Poulson has been a freelance journalist since 2009. Her arts and entertainment reviews can be found in The Examiner. Poulson holds a Bachelor of Arts in creative writing from Arizona State University.