You've probably noticed the glass bottles used for beer are often brown or green glass.
That's thanks to a chemical reaction no beer lover likes: skunking.
If the hops in beer are hit with strong light, something called a photooxidation reaction takes place. That results in a funky taste not unlike the smell of a skunk, hence the name.
In the 19th century, brewers turned to glass bottles to keep the beverage fresh.
Eventually they noticed the beer still had bubbles but developed a bad taste. They eventually switched to brown bottles to block out the UV rays.
After World War II, brown glass was in short supply so some brewers, especially in Europe, turned to green glass.
You may be asking right now about the beer bottled in clear glass, because we do now have brands that use clear bottles.
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That's because technology has advanced and some glass suppliers apply a clear UV protection coat to bottles, protecting the precious beer inside.
Still, most brewers will tell you if you want to store beer for any period of time, keep it in a cool dark place.