How Glass is Recycled

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How glass is recycled
Creative Commons License photo credit: Orin ZebestI

As with a lot of materials that are recyclable, it’s good to know a little bit about how they’re made in the first place. Glass is formed from naturally occurring ingredients that are heated and then cooled and shaped using various methods. How glass is recycled is related to how it’s made.

Have you ever seen glass blown? It’s pretty fun. It’s just silica from sandstone, lime from limestone, and some other powdery stuff like baking soda to lower its melting point since it has to be heated to 2,500° F.

Why Recycle Glass

When glass is recycled, it’s crushed into what’s called “cullet.”  Any metal caps and paper labels are separated first by the processor. Less energy is used because this new, crushed glass melts at a lower temperature than when you first make glass.

Glass is a lot like aluminum in that it can be recycled forever, without losing its glassy charm. Also like aluminum, glass bottles and jars go from recycling bin to the store shelf with a short turn-around time. (As little as 30 days.) More good news is that most curbside recycling programs accept glass. Now you know a bit more about how glass is recycled!

Two things to remember when recycling glass:

1. If you throw light bulbs, ceramic pottery such as coffee mugs, or mirrors into the glass bin, it can put a serious kink in the manufacturing process- damaging the glass-making machinery or creating sub-standard glass containers that are not usable. Here is a short list of common contaminants.

2. You may have to separate the clear from colored glass.

There are a few different colors of glass you may have noticed as you sip your beer, wine, or old-timey soda pop. There’s glass that has no color at all- it’s clear, like sauce or other jars, then blue, brown, and green glass. Colored glass is made by adding chemicals into the mix, or from metals like copper, nickel or iron. For example, the amber or brown glass you see used in beer bottles gets its color from iron sulfide. Iron-chromite creates shades of green, while cobalt makes shades of blue.

Color matters because of wanting to protect whatever is inside from light or temperature. That’s why wine glasses are normally green, and beer glasses are usually brown. Harder liquor bottles sometimes have blue glass. Since colored glass equals clear glass plus chemicals or metals, only clear glass can be recycled into clear glass containers.

Glasstacular: How Glass is Recycled

Glass that is not used to make new containers is used for all kinds of cool stuff, including fiberglass, and a decorative effect for concrete. Reflective paints contain thousands of little glass spheres.

Glass "G" Recyling LogoLook for the Recycling “G” logo on glass packaging, which means it is made from recycled glass.

Depending on what state you live in, you may have noticed that you pay a deposit for your glass bottles, which can be redeemed when you take the empty bottles back to the store. This is an incentive to ensure a high rate of recycling or reuse and you can find loads of information about that at the Bottle Bill Resource Guide.

The Glass Packaging Institute has some great information on their site.

Fun dictionary term: Glassphalt is responsible for that shimmer you see on sidewalks. An alternative to asphalt. Who knew!

Celebrate Recycle Glass Week annually in September.

For a treat, check out the interview we did about the beautiful recycled glassware created by Fire & Light.

Online Games

Who says you have to be in 4th grade to learn from Captain Cullet?

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