Bourbon Proof gets higher as it ages

[DrinkyBanjo]

I read this somewhere that the proof of Bourbon increases in the barrel as it ages. Is this true for whiskey or just Bourbon? If it's only Bourbon then why would that be?

[kbuzbee]

It is true (generally) and it seems to hinge on the different rates of evaporation through the wood of water and alcohol (maybe based on molecular size?) Example would be Stagg which probably goes into the barrel into the barrel at say 120 and come out at 140 or so. I haven't seen similar data for others like Scotch but in the dimmly lit recesses of my mind I think I read once the proof goes down in the barrel. I have no idea why things might work differently. Maybe the cooler climate??

Ken

[fricky]

I believe that there have been prior discussions concerning why bourbon proof increases over time. I would have thought that since alcohol is more volatile than water, the proof would decrease. That is apparently incorrect. Based on prior comments, it is my understanding that the water molecule is smaller than the alcohol molecule and therefore over time, water evaporates thereby increasing alcohol content. That must be a major disappointment for the angels.

I would assume the same occurs in other aged distillates; however, there are many on this website that are much more knowledgeable and will proably provide better detailed descriptions of what takes place during aging of various distillates.

Doug

[doubleblank]

There is indeed a long thread here discussing the "race" to escape the barrel and who wins depends on many factors including molecule size, atmospheric conditions (humidity and temp), etc. I'm just too lazy to search it out....but it wasn't but about a year ago as I recall.

Randy

[tdelling]

> I read this somewhere that the proof of Bourbon increases in the barrel

> as it ages. Is this true for whiskey or just Bourbon? If it's only Bourbon

> then why would that be?

It has to do with environment. In relatively humid environments (Scotland),

the water loss is slower than the ethanol loss. Thus proof goes down.

The opposite happens in (relatively dry) Kentucky.

It's all about the humidity in the environment.

Put one piece of wet cardboard in a humid room, and one in a dry room.

Which one dries faster?

The "water is a smaller molecule" theory is a good idea, but it's wrong.

It's been shown that molecular size has pretty much no effect on how

fast a molecule goes through a whiskey barrel.

Tim Dellinger

[Ken Weber]

I believe you are correct regarding Scotch. The proof does decline over the years. This presents a very interesting problem. I may be suffering from a poor memory, but I believe that Scotch can not be bottled at less than 80 proof. If a scotch is aged for 40 years, and if it went into the barrel at a relatively low proof, what happens when it drops below 80? Blending a 40 year old with younger whisky would be a terrible thing to do!

Ken

[kbuzbee]

Great question. I have no idea. I only drink a couple Scotchs. Not a regular thing by any means... Maybe someone closer to that industry has some input. I would guess they have a good handle on the amount of reduction and barrel accordingly. Seems logical. You are absolutely right. "diluting' a 40 yo to get the needed proof is just wrong.

Ken

[TNbourbon]

Not an expert (kinda goes without saying, huh?) here -- I, too, only keep a few scotches around for occasional change-of-pace -- but I believe I've read that (presumably higher-proof) GNS and grain whisky can be used even in single-malt scotch production, and that it is aged alongside the whisky itself, so any blending is from like-aged stock.

If that's completely wrong, I can count on someone here knowing the straight scotch (SS.com? ) scoop.

[voigtman]

Not an expert (kinda goes without saying, huh?) here -- I, too, only keep a few scotches around for occasional change-of-pace -- but I believe I've read that (presumably higher-proof) GNS and grain whisky can be used even in single-malt scotch production, and that it is aged alongside the whisky itself, so any blending is from like-aged stock.

If that's completely wrong, I can count on someone here knowing the straight scotch (SS.com? ) scoop.

Single malt scotch cannot contain added GNS or aged grain whisky: it has to be pot still whiskey from one distillery and the mash is 100% malted barley. Blended scotch is another matter: that can contain grain whiskey that meets the minimum age requirements. As for what happens when SMS whisky gets down near 40% ABV (80 proof), it either has to get bottled as whisky ASAP or can be used as a reducer (Springbank has done this on occasion, at least once by accident, e.g., the Springbank 12, 100 "double dark" released years ago) or it can be allowed to fall below 40% and then become a liqueur. Maybe there are other options, but I think these are the main ones. Presumably, the very small amounts of 50 or so year old SMS in Johnnie Walker Blue are this old SMS that got near or below the 40% ABV mark. Cheers, Ed V.

[TNbourbon]

Well, there you go! Thanks, Ed.

[DrinkyBanjo]

Thank you all!