will it oxidize?

As long as the bottle is at least half full, it shouldn't oxidize too quickly. Some single malts don't change that much as they sit with air in the bottle, others do. Some mellow out in a beneficial way or a new part of their character is revealed. Usually, when my bottles get below half full, I will decant a good portion of the rest into two sample bottles filled full. Should, I think, stop any oxidization as long as they're not opened a lot.

@WmRamsey thanks for the advice much appreciated.

Once it has dropped below a certain level, it will still take several months (sometimes years) before it starts to oxidize. It will never go bad, by the way, only does the flavour composition change slightly. Glenfarclas 30yo is too good to worry about this, it will be empty before you need to worry.

I recently tasted a Tomatin 5 Year Old, that was bottled in the 70's of the previous century. It was my first encounter with the so-called OBE - Old Bottle Effect. In this case, I got a whiff of new gymshoes and mushrooms on the nose that only disappeared after a good ten minutes. But the whisky still tasted very good, so I guess the effect was minimal.

Yes but we're talking about open bottles. OBE occurs in closed bottles, due to interaction with the glass / air / sunlight.

I know this thread is old, but I think it's OK to ask you guys here about the oxidation in whisky bottles. How is this exactly working? Why will it be a bigger problem, if there is more air in the bottle? The surface of the whisky, which is interacting with the air, keeps nearly the same...

Hope you can help me out here.

@Wills I don't think anyone really knows the how or why. Here's my personal theory: Molecules are always volitalizing (evaporating) off the surface of the whisky, and then mixing with the air. This is definitely happening - that's why you can smell whisky. Some molecules come out of the fluid and into your nose. As there is more air and less whisky in the bottle, a relatively higher amount of volatilization can occur at a faster rate, because there is more air available for the whisky-gas to reach equilibrium with. I think that a big contributor to the decline of whisky is each time you open the bottle, all of this whisky-gas in the bottle leaves, and is gone forever, and then more whisky evaporates to fill the space, and then you open the bottle again and that stuff is gone, etc. Thus, I think that this evaporation-mechanism is probably at least as important as actual "oxidation" or the breaking down of flavor compounds within the whisky. Additionally, the alcohol may evaporate at a faster rate than the rest of the fluid, reducing the ABV over time which could change the flavor profile.

As someone mentioned in this thread, the unfortunate truth is that this is fairly unpredictable at what rate it'll happen. If you really care about the nuance of flavor in your whisky, then you should probably drink within a few months or decant into smaller bottles. If you don't really care, then take your time. I did some experiments once comparing some whisky I decanted into miniature bottles with the full bottle over time. There are noticeable differences after 2 or 3 months, but whether or not those differences are significant enough to make you worry depends on you and the whisky.

@valuewhisky: Excellent reply! There are some other considerations that come into play, namely keeping the opened bottle in a cool, dark storage where, as best as possible, the temperature is, more or less, even. I know the Glenfarclas 30yo. and it does not take kindly to water (even the best of them).

This Whisky will change enormously in the glass and will tell you much more about itself, if you take your time. If you have the time, pour a glass anything up to several hours before you plan to drink it, cover and set aside, again in a cool dark place. Remove the lid; any clean cover will do, ( the lid off the G/F30 will work) about 10 min. before you plan to drink it. You can play with your Whisky for an hour or so; and this Whisky deserves time and it will reward you 'in spades'.

Slainte!

@valuewhisky I can say, through experience (and an experiment conducted with 2 friends) that merely opening a bottle regularly has the effect you mention of upsetting the liquid-vapour-air equilibrium such that whisky degradation / oxidation occurs at a faster rate.

The experiment involved the same whisky decanted at the same time into two identical smaller bottles with same whisky to air ratio. Over a few months, one was opened once a week to simulate a "pour" (without actually pouring the whisky) and another was left alone, unopened.

In a blind tasting, with random sampling order, all three of us picked the "oxidised" whisky immediately and with great conviction - the difference was very apparent. Long story short - merely replacing the air on a regular basis will adversely affect the whisky, let alone worrying about how much air there is in the bottle as a "full" bottle opened regularly will degrade faster than a bottle that remains untouched.

A handy hint that I can ascertain out of all this is to decant from your original bottle immediately or within a month of first opening (when a whisky might actually still improve with air interaction), into a full smaller bottle with a tight cap and DO NOT OPEN until you wish to drink it - and by that, I mean, until you commit to drinking it all rather quickly once open. I regularly fill at least one (sometimes two) 25cl bottles from a recently opened original 70cl bottle so that I can enjoy some a little later and some a lot later (say, 6 months from now).

@valuewhisky Thx for the very nice reply!

@A'bunadhman Why pouring it into the glass (covered) several hours before you want to drink it? Just to get a nice first smell? After a few seconds, the whisky should be the same as if you pour and drink it right away.

@Wills: Not so, especially if you coat the inside of the glass with a gentle swirl or better a gentle tilt! The Whisky will mellow considerably - Give it a try.

Hi my experienced connosr friends :)

I have a question about particular whiskys oxidizing. The question is referring to Highland Park 18yo and Auchentoshan Three Wood. Do you noticed some big changes due to oxidation?

@Wills I don't have any personal experience, but I remembered reading this on Jason Debly's blog re: HP18 (one of my favorite blogs): jason-scotchreviews.blogspot.com/2010/07/…

@Wills, yes, unfortuantely, I have noticed some very strong degenerative changes in HP 18 after about 8-9 months of the bottle being open. I would be very careful with that one.

Thx, that's good to know!