Why are beer bottles brown?

Why are beer bottles brown? It is one of those questions we never thought to ask … until someone pointed it out. That someone is the Business Insider, which has done a short, but revealing article that proves beer bottles aren’t brown by accident or because it makes them look more manly.

“Beer has been around for quite a while — some of the first to brew it was the ancient Egyptians thousands of years ago,” says the Business Insider. “However, bottled beer only started to be a thing in the 19th century, when brewers realized glass would keep it fresh.”

Brewers soon discovered that when beer is stored in clear glass, it starts to smell “skunky” when left in the sun for too long, says the Business Insider.

“This was because the clear glass allowed UV rays to penetrate the beer and alter the flavor.”

Popular Science backs this up, by noting the bittering agent generated from hops while boiling beer wort is a compound that can be degraded by ultraviolet light.

The solution was making the bottles a darker color, to block out the rays. The Business Insider says green bottles became popular after World War II, due to a shortage of brown glass.

The tradition could change in the future, says the Insider, since brewers can apply UV protected coats to glass to preserve taste.