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Beer has been around for quite a while – some of the first to brew it was the ancient Egyptians thousands of years ago. However, bottled beer only started to be a thing in the 19th century, when brewers realised glass would keep it fresh.
Beer was stored in clear glass and when left in the sun for too long, it started to smell "skunky" – like a skunk, literally. This was because the clear glass allowed UV rays to penetrate the beer and alter the flavour.
The solution was turning bottles brown, a darker colour which would block out the rays. After World War II, green bottles also became popular due to a shortage of brown glass.
These days, brewers can apply UV protected coats to glass to preserve the taste.