Beer bottles come in a variety of colours, whether it be clear, green, or brown. Often the brown beer bottle is a varying shade of dark amber, or even almost black. Regardless, the colour of a beer bottle is more often than not some sort of dark brown. It’s the minority that are a green or a clear, and honestly, beer that comes in a green or clear bottle isn’t usually tasty craft beer anyway.

Why Beer Bottles Are Brown

Looking through some history, the Professor’s House claims that early glass making technology made it difficult to create clear glass. So most early glassware wasn’t clear in the first place, it would have been brown or some other dark colour. Clear glass and other colours didn’t become a think until much later.

But there’s another beneficial reason beer bottles are brown, but it’s hard to say whether they’re brown because of this.

Brown beer bottles happen to do an excellent job of blocking UV light. While this has been known, Wired did a nifty at home experiment that showed this pretty well. When compared to green or clear coloured bottles, the brown beer bottles let through virtually no UV light, while the clear and the green let through quite a bit of UV.

UV blocking is important as its these wave lengths of light (300-500 nm to be precise) that convert compounds in hops to 3-methyl-2-butene-1-thiol or MBT. MBT gives beer a skunky taste and smell. And by skunky, we mean smelling of a skunk. The chemical is similar to that in the spray of a skunk! Humans are designed to not like it very much, so we can tell quite easily when it’s there. Some have also equated this taste and smell to that of cat urine. Yum!

Beer that have been exposed to too much UV are often referred to as lightstruck or simply skunked. The actual chemical reactions behind lightstriking get a bit complicated, but Popular Science outlines it pretty well for laypeople.

What is easy to explain, however, is that different beers will be affected differently from UV light, since different beers have different amounts of hops and other compounds in them. It really depends on the balance of all these things and how the chemistry goes!

However, many people like to say the beer bottles are brown because they’re designed to filter out UV. This probably isn’t the case. As mentioned, bottles were probably originally brown because it was easier to make them this way, and they continued to be brown out of tradition. Skunking, of course, was a problem is those day, but they didn’t know what was causing the problem.

How Much of a Problem is Skunking?

It’s really only a problem to the extent that beer drinkers let it be a problem.

In researching this article, one source claimed that beer can get skunked “within minutes,” which seems doubtful, considering the amount of beer we’ve all had sitting outside on a beautiful summer’s day. It’s a chemical reaction, and chemical reactions take time.

Most sources also cite how skunked Corona is, since it’s in a clear bottle. And this seems generally correct, but it’s not an exceptionally skunked beer. Is this why the tradition of putting a lime in it came about? That’s what a lot of people are saying, but it seems doubtful. It’s not a beer known for having tons of hops after all…

Adding to this, some mass produced beers use a hop extract that avoids the chemical reaction that causes the skunking in the first place. This is why a lot of macro-beers can afford to be in clear or green bottles, and we’d never know! That and the hop profile in these beers is low, there’s not much to react with.

So watch out! Keep your beer in the dark, and you’ll enjoy it a whole lot more.