Question on evaporation

[ggilbertva]

Anyone have thoughts on when a bottle should be opened once evaporation reaches a certain point? I have a number of older bottles that have lost content anywhere from 5-20% (approx). Is there a point where oxidation really begins to accelerate the demise of the whiskey?

[TNbourbon]

Personally, Greg, I've never found a bottle anything more than 'almost-empty' I thought suffered oxidation before its original uncorking. But, I've opened quite a few 'oldies' as much as a stop-loss measure as anything -- it's only going to get lower, and probably not much better!
And -- you may well have accounted for this already -- but keep in mind that what looks like 20% at the top of a bottle can often actually be only 7%-10% because of the bottle's shape. For example, I have an early-'50s Old Grand-Dad that keeps tempting me to open it (maybe, in part, because I've had some 'Wow!' OGDs from that era, too!) because it's down 2 inches in the neck and upper shoulder, but the particular decanter (glass) flares broadly in the middle, so those 2 inches at the top really aren't as much as they seem.
Take a grease pencil (if you want to keep the bottle, it rubs off) and mark/date the fills -- if you see one move noticeably in a short period, open it.

[ggilbertva]

Tim,

Thanks for the response. I appreciate the guidance.

[cowdery]

I concur with Tim on every point.

If, however, you have noted evaporation during the time you have had a bottle, you don't necessarily need to hurry up and drink it, but you should take steps to upgrade the seal and prevent any further loss.

[TNbourbon]

...If, however, you have noted evaporation during the time you have had a bottle, you don't necessarily need to hurry up and drink it, but you should take steps to upgrade the seal and prevent any further loss.

Excellent point -- and I have more than a couple of bottles with Parafilm-M literally holding down the cork.

[ggilbertva]

I haven't noticed any further evaporation. The cord looks good and I believe the seal is in good shape also. Tim, to your point, because of the shape from the neck to the fill point, it may well be somewhere around 8-10% loss. The bourbon was bottled in 1959 so I figured that much loss in 49 years isn't too bad. My only concern was to the quality of the bourbon inside due to oxidation. I didn't want it to turn because of the evaporation.

[tango-papa]

...The bourbon was bottled in 1959 so I figured that much loss in 49 years isn't too bad...

Ooh, whatcha got from 1959? Huh, huh, huh?

~tp

[ggilbertva]

My bottle of Old Forester BIB was distilled in 1952 and bottled fall of 1959. This is a picture.

[cowdery]

One thing Tim said that is exactly what I have experienced is that most times I have experienced (i.e., tasted) oxidation damage, it has been from a bottle that contained mostly air, not just a larger-than-normal air gap at the top. Or it was a decanter.

[gblick]

It seem logical to me that whatever air that is in the bottle will cause some oxidation, but after a while the actual oxygen content in that air will be depleted making that air 'neutral'. Any more airspace, created by evaporation, will most likely only let a very small amount of 'fresh' air in, which IMO is not going to be enough to worry about since the majority of the air still in the bottle has long had it's oxygen depleted.

Now when you've got bottles that you're drinking from it's entirely different, because every time you open it and pour a drink, a lot of the depleted air escapes and is replaced with fresh air containing more oxygen, which will cause further oxidation.

Does that make any sense?