How Glass Recycling Works

Glass is a fascinating material. Although it seems solid and shatters when hit, it never loses all of its liquid properties, which is why very old glass windows are wavy. It can be recycled over and over again and still be as strong and useful as ever. It does not absorb tastes and stains.

Glass is one of the oldest recyclable, man-made materials on Earth. The ancient Egyptians made glass, and broken glass was melted down and reused. It can be made into an amazing number of items, including an alternative to pavement (“glassphalt”), construction sand, containers, bottles, lenses, and other items.

But how does all this happen? What happens when your glass gets to the recycling center? Here is a brief explanation of what happens to all that glass.

1. Separated into colors

Once a chemical pigment is added to glass to make it colored, it can not be removed. Thus, green glass can only be used to make green glass items, brown glass can only be recycled into brown colored items, etc. This is why the recycling plant separates the colors. If glass is contaminated – i.e., colors have been mixed or foreign materials have smirched the glass batch – then it can be used to make insulation or other items where color and purity are unimportant.

This is a good reason to take care not to mix unrecyclable glass with recyclable, or even to mix certain recyclables. Light bulb glass, for example, should not be included with glass bottles. (And squiggly CFL light-bulbs need to be recycled in a completely different way, by the way.)

2. Crushing

The separated glass is then crushed by machines, and is then called “cullet.” The cullet is mixed with soda ash, silica sand, and limestone. (These are the ingredients used to make glass as well.) Then the cullet is sent to the furnace.

3. Heating

The cullet mixture is heated in a furnace until it is a red-hot, thick liquid about the consistency of honey. At this point there is no substantial difference between the recycled glass and glass that contains only the original raw materials.

4. Molding

The liquid glass is then poured into molds. Air is blown into the molds to make the proper shape. Some gla

ss is hand-blown and made into artistic pieces, decorative bowls, Christmas ornaments, etc.

5. Shipping

The new glass containers are then shipped to various businesses where they are sold as-is or filled with various liquids, foods, etc. The entire process – from drop-off to the appearance of glass containers on shelves – can take as little as 30 days.

What else is it used for?

Glass is quite versatile. As mentioned above, it can be made into “glassphalt” and construction sand. In fact, glass is made from sand and can be ground back into that material easily. It can be “spun” into thin, flexible threads (fiberglass) and pressed into insulation. Glass can be recycled indefinitely.

Filed under: Glass

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