Can Whiskey Evaporate in a Glass or (Closed) Bottle?

Whiskey, although delicious, can be expensive. Every drop of whiskey lost is a waste, and therefore I wondered if the whiskey evaporates. If it does, how can I stop this? I did my research and found the answer!

Can whiskey evaporate?

Yes, there are volatile substances in whiskey that evaporate when in contact with air, for example the alcohol. If a glass of whiskey is left overnight, the change in flavor will be noticeably different and flatter. A bottle, if sealed airtight, does not risk evaporation.

But the evaporation of whiskey does not necessarily have to be disastrous. You just know what you are doing, when evaporation is the worst and what measures to take to keep enjoying your whiskey as long as possible.

What happens when a part of the whiskey evaporates?

When whiskey is exposed to air, evaporation slowly takes place. Many people describe the interaction between whiskey and air as oxidation. A big part of the oxidation process is evaporation, and the result on the flavor of the whiskey is often described as just a shadow of its former self.

This change in flavor can happen to a glass of whiskey you poured and forgot about, but also to bottles that are stored with too much overhead air in the bottle.

Whiskey generally has a rather high alcohol percentage starting at around 40% Alcohol By Volume (ABV). Because of this percentage, the whiskey is good at killing bacteria. Whenever the alcohol from the whiskey evaporates the product becomes more susceptible to bacterial contamination.

Evaporation in a bottle of whiskey

When a bottle of whiskey is not sealed airtight, your whiskey will oxidize over time. An unopened bottle of whiskey does not have an infinite shelf life like many people assume. Stored under the proper circumstance the shelf life can be extremely long (decades) but there are some factors that influence the evaporation in a bottle of whiskey.

1. The seal of the bottle

Ideally, the bottle of whiskey should be stored completely airtight. Once the whiskey leaves the cask and is bottled, the whiskey is a finished product. Unlike a fine wine, the flavor of the whiskey does not improve in the bottle. In the ideal case the bottled whiskey does not come into contact with any air until you pour yourself a dram.

However, a cork is an organic material that is prone to be the bottleneck in preventing evaporation of your whiskey. Always store your bottle of whiskey upright, as the cork can be damaged and even be deteriorated by prolonged contact with the alcohol in the whiskey.

Another risk that comes with using cork as a seal is the risk of completely drying out. The cork needs to remain moist in order to be an airtight seal, so if you do not plan on drinking a whiskey anytime soon make sure to hold your bottle upside down every couple of months to keep the seal airtight.

Often, people associate whiskey that is kept in a bottle with a screw cap as inferior or low quality whiskey. This is not the case! I repeat, whiskey that comes in a screw cap bottle is not by definition inferior whiskey. However, let’s not forget that cheap whiskey often comes with a screw cap.

Johnnie Walker Black Label bottle cork on whiskey bottle close-up. Johnnie Walker is Scotch blended whiskey and one of famous brands in world

While screw caps are a better airtight seal compared to cork, they do risk loosening up over time. If you are a collector or have a lot of bottles, make sure to tighten your screw cap bottles once a month to prevent oxidation and evaporation.

2. The amount of overhead air in a bottle

When you have been enjoying a whiskey the bottle will be emptier. Wow, I figured that one out all by myself. But what effect does this have on evaporation? Well, a bottle that is 50% full is exposed to more air than the same bottle filled for 70%. More air in the bottle is more oxidation, and therefore the taste of the whiskey will change quicker.

How should you reduce or manage this oxidation? The first way is to drink your whiskey quickly after the bottle is over 50% empty. I recommend drinking the last half of a bottle withing 3 to 4 months, just to be sure. But what if the whiskey is super expensive, or there is another reason you do not want to drink it?

In that case, find yourself a smaller glass container with an airtight seal. This can be a bottle that used to hold apple juice or milk or whatever. Make sure to thoroughly clean and rinse it, but after that they are perfect to store the remaining whiskey.

Does whiskey evaporate in a decanter?

People often think you can store whiskey in a decanter just as long as you would be able to store it in its original bottle. This is not the case, as decanters often are not airtight at all. If the decanter would be airtight, there is no problem (unless there is a lot of overhead air in the decanter).

There is another risk that comes with storing your whiskey in a decanter, and that is when you are using a crystal decanter. Crystal glass contains lead, which can contaminate and dissolve into your whiskey. Therefore, make sure you never store your whiskey in a crystal decanter ever. Instead, use a beautiful crystal decanter as a way of serving your whiskey to a group of people. I have written an article that goes into way more detail about whether or not you should decant your whiskey.

If you want to decant your whiskey, make sure to use a glass decanter with a glass stopper. There are glass decanters with plastic stoppers, but those are not airtight at all as the glass can expand and contract because of temperature whereas the plastic seal can not.

How long does whiskey last if unopened

Though not infinite, the self life of unopened whiskey will be multiple decades if stored properly. Store your whiskey in a dark, cool, temperature stable location where sunlight can not reach it. Unopened, the whiskey can last very long there. When opened, make sure to not leave too much air in the bottle.

It is crucial that you store your whiskey correctly, as it is not that difficult and preserves your precious drink. I have written a brief guide to storing whiskey in my article “Can Whiskey go Bad? All you need to preserve the taste“. Make sure to check it out and see if you are doing everything correctly.

Does whiskey expire?

Some distilleries might choose to add an expiration date to the bottle. If so, the only reason is to create more consumer trust in their product. We have just learned that an unopened bottle can last you extremely long, so do not let an expiration date fool you.

Someone holds a bottle of 16 years aged Lagavulin single malt whisky at the Lagavulin whisky distillery with old oak cask on the background.

Whenever you are in doubt whether your whiskey is still drinkable, please use your common sense. If the whiskey is cloudy or moldy, do not drink. If it looks fine but tastes nothing like you remembered, chances are the whiskey is oxidized but fine to drink. If the whiskey tastes fine, go ahead and pour yourself a dram, enjoy!

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