Those tiny bubbles you see on the inside wall or the surface of your decanter? Basic chemistry. When the temperature of the decanter is lower than the outside air, condensation happens, and what you see is the water vapor in the air turning into liquid form. The same concept works in reverse; when the moisture inside the container is cooler than the air outside it, you see tiny bubbles form on the inside.
Generally, this should not cause any concern, but for all the doubting Thomases out there who are worried about the effects of condensation on how they drink alcohol, allow us to shed some light on this inconsequential yet recurring issue.
Outside vs inside condensation
Water vapor is always in the air. Warm air carries more water vapor, which is what we call humidity. The maximum amount of water vapor that the air can hold corresponds to 100% relative humidity (also called dew point), at which point the air is considered 'saturated'.
Thus, when a parcel of moist air is cooled, the humidity will rise until it reaches the dew point, and the excess water will condense out of the air in the form of liquid droplets.
Condensation outside the decanter
First of all, that’s not alcohol that just magically appeared on the surface of your decanter in the form of droplets. That’s just water. But how did it get there?
Those droplets literally came right out of thin air. Again, water vapor is everywhere, and when it comes into contact with something cool, such as the outside of a cold whiskey decanter, its molecules slow down and get closer together. As it happens, the water vapor (in gas form) turns back into water droplets (in liquid form). Voila, that’s condensation.
Here’s another way to look at condensation: If you’re wearing glasses and you’re indoors where it's cool and then suddenly you walk outside and stay under the sun, your glasses will fog up. This is because water vapor in the hot outside air condenses on the cooler surface of your glasses.
Particularly during fall and spring, when temperatures vary more than at other times of the year, you may notice condensation on the walls or windows of your house. You can also see it on the windows of your car. These are all examples of the same scientific process of condensation. Unless of course, if you’re using anti-fog glasses.
So now we know that those bubbles that form on the surface of the decanter are pretty normal. But have you ever noticed the same thing happen, except inside the decanter? How could that happen when there’s no atmosphere inside, especially when the decanter is sealed airtight?
The explanation is pretty much the same, but this time it has more to do with the vapor pressure of the alcoholic beverage inside the decanter. The "air" in the bottle is actually alcohol vapors, the most common of which is Ethanol. Some of the alcohol vapors evaporate out of the solution and this creates pressure. This is also why when you open a bottle of soda, you get a loud hiss from the top.
When the decanter cools to the ambient environment, the alcohol vapor pressure inside the decanter is lowered. This lowers the temperature at which the alcohol boils, which results in the concentration of alcohol in the vapor. So even when your bottle is just chilling there, the evaporated alcohol vapor condenses on the inner sides of the bottle. You’ll see that as though the bottles are sweating on the inside.
The likelihood of this happening depends on several factors such as temperature, the shape of the decanter, and the type of drink inside it. It is also a sure sign that the seal on that decanter is airtight. The tighter the seal, the less likely it is for the air inside it to escape, therefore resulting in condensation.
Is condensation bad for your drink?
In theory, the answer is no. Those bubbles, as we have established, are only water. The bubbles inside the decanter are just the alcohol vapors that turned into liquid. So technically, there are no substances that could harm someone who drinks alcohol from a decanter with condensation.
As a matter of fact, condensation inside the decanter is a sign that the drink has been contained effectively, thus the quality is most likely still good.
On the flip side, several factors facilitate condensation to happen and one of them is time. Some people think of condensation (particularly condensation outside of the container) as an indicator of time passed. Would you want to drink any liquid that had been in the backseat of your car for a week?
So if you think about it, it all boils down to the quality of your decanter and how effectively you can seal it to ensure the drink will not go bad. If you’re looking to use a crystal decanter, make sure you study how long you can leave alcohol inside it and still be able to drink it worry-free.
Condensation is a naturally occurring chemical reaction caused by the changing temperatures and the interaction of moisture from different environments. If there’s any indication that it’s harmful to drink from a container where there is condensation happening, then we should have heard about it from health experts, but we haven’t. Until then, enjoy your drink!