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Jackie
03-24-2009, 09:45
We are of the opinion that the alcohol in bourbon becomes more intense with aging - or that the proof becomes higher. A friend disagreed and said he thinks that the alcohol content becomes less with aging. Are either of us correct, or does the length of aging not affect the amount of alcohol at all? Thanks.

kickert
03-24-2009, 10:13
We are of the opinion that the alcohol in bourbon becomes more intense with aging - or that the proof becomes higher. A friend disagreed and said he thinks that the alcohol content becomes less with aging. Are either of us correct, or does the length of aging not affect the amount of alcohol at all? Thanks.

You both are right. In general, a bourbon aged in alcohol increases in proof as it ages. However, that is not always the case. I hear that scotches actually decrease in proof.

At a recent distillery tour I went on, I was told the higher barrels in a warehouse significantly increase in proof because of the higher tempature and lower humidity. Conversely, barrels stored on the bottle floor tend to lower in proof in the cooler, higher humidity areas.

squire
03-24-2009, 19:20
Hey Jackie, welcome aboard. Whiskey aged in warehouses under the warm Southern Sun will increase in alcohol, though not at the same rate depending on placement in the warehouse. Whiskys aged in the colder climate of Scotland will decrease, but again not at the same rate for each barrel. Doesn't really affect the final product though, that is the province of the Masters who choose the barrels to be mingled into a certain profile.

Squash
03-24-2009, 19:57
The proof increases in warm climates because the water molecules are smaller than the ethyl alcohol molecules, and therefore they have an easier time getting through the oak and out to the air. So more water loss than alcohol loss yields higher proof.

In the cooler climates, the water that gets through the oak does not want to jump into the air (evaporate) as much because of the lower temperature and the high partial pressure of water in the air - the air is already holding as much water as it can. This is why we don't dry clothes with cold air. The alcohol is much more volatile, and can still jump into the air at lower temperatures, and the partial pressure of alcohol in air is near zero, so there's plenty of room for more alcohol in the air. The alcohol leaves more than the water - decrease in proof.

smokinjoe
03-25-2009, 06:01
The proof increases in warm climates because the water molecules are smaller than the ethyl alcohol molecules, and therefore they have an easier time getting through the oak and out to the air. So more water loss than alcohol loss yields higher proof.

In the cooler climates, the water that gets through the oak does not want to jump into the air (evaporate) as much because of the lower temperature and the high partial pressure of water in the air - the air is already holding as much water as it can. This is why we don't dry clothes with cold air. The alcohol is much more volatile, and can still jump into the air at lower temperatures, and the partial pressure of alcohol in air is near zero, so there's plenty of room for more alcohol in the air. The alcohol leaves more than the water - decrease in proof.

Nice work, Squash. Now, if someone will confirm this, (it sounds good to me)I can put this page in my Bourbon Bible.
:toast:

Josh
03-25-2009, 10:49
The proof increases in warm climates because the water molecules are smaller than the ethyl alcohol molecules, and therefore they have an easier time getting through the oak and out to the air. So more water loss than alcohol loss yields higher proof.

In the cooler climates, the water that gets through the oak does not want to jump into the air (evaporate) as much because of the lower temperature and the high partial pressure of water in the air - the air is already holding as much water as it can. This is why we don't dry clothes with cold air. The alcohol is much more volatile, and can still jump into the air at lower temperatures, and the partial pressure of alcohol in air is near zero, so there's plenty of room for more alcohol in the air. The alcohol leaves more than the water - decrease in proof.

I agree w/joe. That's the first reasonable explanation of the phenomenon I've heard. Well done squash!

barturtle
03-25-2009, 12:52
Here'a nice couple posts by Tim Dellinger:

The first one (http://www.straightbourbon.com/forums/showpost.php?p=48897&postcount=5) shoots down the whole water molecule theory

And the second (http://www.straightbourbon.com/forums/showpost.php?p=48384&postcount=75) is a more complete explanation.

EDIT: Actually the whole thread (http://www.straightbourbon.com/forums/showthread.php?p=48379#post48379) that the second post is on is worth a read.

EDIT 2 here's a third one (http://www.straightbourbon.com/forums/showthread.php?p=49683#post49683)

Josh
03-25-2009, 13:01
Here'a nice couple posts by Tim Dellinger:

The first one (http://www.straightbourbon.com/forums/showpost.php?p=48897&postcount=5) shoots down the whole water molecule theory

And the second (http://www.straightbourbon.com/forums/showpost.php?p=48384&postcount=75) is a more complete explanation.

EDIT: Actually the whole thread (http://www.straightbourbon.com/forums/showthread.php?p=48379#post48379) that the second post is on is worth a read.

EDIT 2 here's a third one (http://www.straightbourbon.com/forums/showthread.php?p=49683#post49683)

I'm sure ppl much smarter than I are saying "aha! now I get it!" but I could really use an executive summary of these posts. Having trouble following the whole thing.

Squash
03-25-2009, 14:08
If temperature and humidity were the only factors involved here, all spirits would loose proof as they aged in wood barrels because alcohol evaporates faster than water in all aging environments (Scottland, Kentucky, etc...).

The idea that water evaporates faster that alcohol in Kentucky, as Tdelling stated, is not true. If you don't believe this, take a glass of Stagg and a glass of water and put then in your attick on a warm, summer's day (similar to the environment where bourbon gains proof). I think we all know the result, so don't waste your Stagg.

Barreled Stagg gains proof. Open Stagg looses proof, quickly. Bottled Stagg has constant proof. Since we can all agree on the above three statements, it must have something to do with the barrel.

The oak barrel must be acting as a partially semipermeable membrane.

barturtle
03-25-2009, 14:57
If you have a membrane, which the barrel certainly is (and I refer to it as such in the second post-I'm the guy with the questions:cool:), and you put two compounds that can both get through it on one side of the membrane and only one of the two compounds on the other side, then only the compound that doesn't exist on the second side will flow across the membrane until both sides have equal amounts of both compounds.

So taking this to whiskey: if you have a location that is extremely damp (like Scotland) the same thing applies, the water in the barrel isn't trying to get across as there is already plenty of water on the other side, but the alcohol will continue to flow through the pores as there is little alcohol on the outside of a barrel (at least in comparison to the amount of water vapor)

Put it in a dry environment and the water catches up and surpasses the evaporation of the alcohol.

Permeability of a membrane is, I believe, and Tim states, unrelated to the size of the molecule. As a matter of fact he quotes a study here (http://www.straightbourbon.com/forums/showpost.php?p=48378&postcount=69) and gives these figures:


Yoahizawa et. at (J Agric Chem Soc Jpn 55: 1063-8, 1981) studied "Subastances
Evaporated Through Barrel of Whisky", and found the following losses over
a given time:

acetaldehyde 32%
ethanol 12.7 %
acetic acid 1.0%

These molecules are very close in size, but very different in barrel
permeability!

Squash
03-25-2009, 18:37
Barturtle: "Put it in a dry environment and the water catches up and surpasses the evaporation of the alcohol." This is only true if a partially (or fully) semipermeable membrane is in place.

Barturtle, you need to waste some Stagg. Please place two fingers of Stagg and two fingers of water in identical glasses and let them sit in your hot attic for one day. Even though we already know the result, we eagerly await.

Are you still willing to stand by your "water catches up and surpasses the evaporation of the alcohol" satement?

callmeox
03-25-2009, 18:44
If the barrels were filled and stored upright with one end open, that would be a valid demo.

barturtle
03-25-2009, 18:50
Barturtle: "Put it in a dry environment and the water catches up and surpasses the evaporation of the alcohol." This is only true if a partially (or fully) semipermeable membrane is in place.

Barturtle, you need to waste some Stagg. Please place two fingers of Stagg and two fingers of water in identical glasses and let them sit in your hot attic for one day. Even though we already know the result, we eagerly await.

Are you still willing to stand by your "water catches up and surpasses the evaporation of the alcohol" satement?

Pay attention:

Yes, the barrel acts as a membrane (as I mentioned way back when) however the membrane is NOT restricting the differences in rate of evaporation between alcohol and water due to the MOLECULE SIZE!

squire
03-25-2009, 18:59
I like the simple explanation, whiskey gains alcohol in the barrel in Kentucky and loses some in Scotland.

Squash
03-25-2009, 19:03
Sorry, I have a lot of attention lapses.

If "the membrane is NOT restricting the differences in rate of evaporation between alcohol and water due to the MOLECULE SIZE!," does the membrane restrict the difference in rate of evaporation between alcohol and water due to anything at all (hydrogen bonding, angels, other)?

barturtle
03-25-2009, 19:40
I like the simple explanation, whiskey gains alcohol in the barrel in Kentucky and loses some in Scotland.

That is only the most common result. There are barrels that drop in proof in KY.

barturtle
03-25-2009, 21:51
Sorry, I have a lot of attention lapses.

If "the membrane is NOT restricting the differences in rate of evaporation between alcohol and water due to the MOLECULE SIZE!," does the membrane restrict the difference in rate of evaporation between alcohol and water due to anything at all (hydrogen bonding, angels, other)?

I'm not sure why you continue to argue this, as your original post and my counter post only differ over molecule size effects. The rest of both explanations relates to temperature and humidity affecting the rate of evaporation. Since Yoahizawa proved that three molecules of nearly the same size cross the barrel at vastly different rates, it just doesn't really matter whether it's hydrogen bonding, selective active transport or Aslan the Lion getting a laugh at the expense of the Scots that causes the difference in rate of evaporation.

squire
03-25-2009, 22:54
Common enough that I feel comfortable with my statement.

barturtle
03-25-2009, 23:18
Common enough that I feel comfortable with my statement.

I'll admit that blanket statements make my skin crawl. But here's a list of bottling proofs for FR 40th that were barreled at 105-110 proof.

151A 105 proof
151B 100.4 proof
151C 104.6 proof

171A 104.0 proof
171B 99.4 proof
171C 102.8 proof
171D 102.2 proof
171F 101.4 proof
171G 101.6 proof

squire
03-26-2009, 07:22
A true statement made your skin crawl? Good Heavens Tim, it's just a hobby.

mozilla
03-26-2009, 07:45
Timothy is correct in his statement regarding barrels of bourbon in Ky do vary in their proof change. Some go up...some go down. The ratio is directly in perportion to where the barrel spends it's time resting. Since, most distilleries don't rotate barrels, these days...it could be said...the ones on the upper floors will gain in proof, to a degree. And the barrels that rest near the bottom floors will go down...to a degree.

Therefor...no commonality to all barrels raising in proof in Ky and all barrels losing proof in Scotland.

barturtle
03-26-2009, 09:25
I would accept the statement:

In General, (or Most Commonly,) whiskey gains alcohol in the barrel in Kentucky and loses some in Scotland.

However, without the "in general" qualification, many, if not most, readers will interpret the statement as "Always" or "Without Exception". It is that kind of carelessness that leads to misguided people thinking that "Bourbon has to come from Kentucky", when what may have been true for a very brief moment in time was that "All whiskies currently being distilled and sold as Straight Bourbon in the United States are made in Kentucky"

squire
03-26-2009, 12:01
Jeff, it would also be accurate to say that the Master Distillers mingle barrels from upper and lower floors/racks/ricks and the resulting whiskey will be higher in proof than it was when first entering the barrel.

barturtle
03-26-2009, 12:24
Jeff, it would also be accurate to say that the Master Distillers mingle barrels from upper and lower floors/racks/ricks and the resulting whiskey will be higher in proof than it was when first entering the barrel.

Oh, once you get to mingling, damn near every whiskey goes down in proof, as they have this tenancy to add water to the batch...

Squash
03-26-2009, 13:54
Barturtle: "I'm not sure why you continue to argue this" - because false statements and impediments to learning are pet peeves of mine.

"In General, (or Most Commonly,) whiskey gains alcohol in the barrel in Kentucky and loses some in Scotland." - False. Whisk(e)y looses alcohol wherever it is stored in oak. The change you are talking about is proof or %ABV.

"Permeability of a membrane is, I believe, and Tim states, unrelated to the size of the molecule." - False. Molecular size is one of the most important factors affecting permeability through a membrane. Get a textbook, or just do some Google searching. It's not open to debate.

The study you quote simply shows that other factors (polarity, solubility, etc...) are in play as well, and this is true. Notice that water was not among the three you listed.

"your original post and my counter post only differ over molecule size effects. The rest of both explanations relates to temperature and humidity affecting the rate of evaporation." - False. My explanation differs from yours, and all others you cite, in that I say the oak barrel (membrane) transports more water than alcohol.

I was told by the distiller at George Dickel that this is due to the difference in size between the two molecules. I believed it because he said it, and because it is in concert with basic science. Whether or not you, I, or anyone else believes that the reason is molecular size is not important. What is important is that people understand that the oak barrel transports water more readily than alcohol for some reason, and that this, in combination with humidity/temperature differences, causes the different changes we see in different locations.

Summing up, an open glass of scotch or bourbon will loose alcohol faster than water in cold, humid Scotland and in hot, dry Kentucky. The decreased permeability of the oak barrel to alcohol compared to water, for whatever reason, is what makes it possible for bourbon to gain proof in a hot, dry environment.

squire
03-26-2009, 15:01
Hey Tim, I seriously doubt even the most casual reader of our posts would be misguided into carelessness by my statement.

barturtle
03-26-2009, 15:06
First, you should really learn how to properly quote, as this would make it much easier.



False. Whisk(e)y looses alcohol wherever it is stored in oak. The change you are talking about is proof or %ABV.

You are correct, I should have said "gains in proof" however, I was just taking the previous statement and making it into something that I would consider acceptable. Alcohol doesn't just magically appear from anywhere.:lol:


False. Molecular size is one of the most important factors affecting permeability through a membrane. Get a textbook, or just do some Google searching. It's not open to debate.

The study you quote simply shows that other factors (polarity, solubility, etc...) are in play as well, and this is true. Notice that water was not among the three you listed.

Water was not listed as the comparison was related to molecules of approximately the same size to demonstrate that molecules of the same size do evaporate at different rates across the barrel. So obviously, in the case of these chemicals, molecule size is not the most important factor. And it also seems that in the "water v. alcohol transport rate" that temperature is a much more important factor than molecule size.

You even point out that in cooler climates water evaporates slower than alcohol, therefore you already have given into the fact that molecule size is by far the less important characteristic effecting the final ABV of the barrel after aging.


False. My explanation differs from yours, and all others you cite, in that I say the oak barrel (membrane) transports more water than alcohol.

No actually you say:


The proof increases in warm climates because the water molecules are smaller than the ethyl alcohol molecules, and therefore they have an easier time getting through the oak and out to the air. So more water loss than alcohol loss yields higher proof.
The second part of your same post agrees with the temperature and humidity based theory:


In the cooler climates, the water that gets through the oak does not want to jump into the air (evaporate) as much because of the lower temperature and the high partial pressure of water in the air - the air is already holding as much water as it can. This is why we don't dry clothes with cold air. The alcohol is much more volatile, and can still jump into the air at lower temperatures, and the partial pressure of alcohol in air is near zero, so there's plenty of room for more alcohol in the air. The alcohol leaves more than the water - decrease in proof.
Let's see..."cooler climate" yup, that's temperature..."high partial pressure of water" that sounds a lot like humidity to me...

"alcohol leaves more than the water"...that sounds a lot like the alcohol is evaporating faster than the water...



I was told by the distiller at George Dickel that this is due to the difference in size between the two molecules. I believed it because he said it, and because it is in concert with basic science. Whether or not you, I, or anyone else believes that the reason is molecular size is not important. What is important is that people understand that the oak barrel transports water more readily than alcohol for some reason, and that this, in combination with humidity/temperature differences, causes the different changes we see in different locations.

Distillers quite frequently state false information, It was quite recently mentioned (http://www.straightbourbon.com/forums/showpost.php?p=163477&postcount=35) how Jim Rutledge had been stating how "Only bourbon made in Kentucky can carry a state name on the label"...until he was called on it and consulted with his lawyers, he has now stricken this statement from all of his presentations. Would 'a distiller' at Dickel be any less likely to quote inaccurate information?


Summing up, an open glass of scotch or bourbon will loose alcohol faster than water in cold, humid Scotland and in hot, dry Kentucky. The decreased permeability of the oak barrel to alcohol compared to water, for whatever reason, is what makes it possible for bourbon to gain proof in a hot, dry environment.

So you're saying that molecule size is not the main governing factor, as I already stated?

kickert
03-26-2009, 15:09
geez fellas.....

squire
03-26-2009, 15:10
Well Tim, of course I meant mingling prior to reduction to bottling proof, thought that might be obvious.

barturtle
03-26-2009, 15:10
Hey Tim, I seriously doubt even the most casual reader of our posts would be misguided into carelessness by my statement.

And if Jimmy Russell was so careless as to make the statement:

"Whiskey gains alcohol in the barrel in Kentucky and loses some in Scotland."

Do you think people on his tours would take him at his word? And if you made that same statement to your friends, who presumably consider you something of an authority, would they take you at your word?

barturtle
03-26-2009, 15:16
Well Tim, of course I meant mingling prior to reduction to bottling proof, thought that might be obvious.

Of course, not all batches of whiskey are mingled from multiple floors. Some batches would be from a single spot in the warehouse where the whiskey was put away for a specific reason, such as an extra aged bourbon like Wild Turkey Tribute.

squire
03-26-2009, 15:23
Tim, I don't ask personal questions nor do I answer them.

squire
03-26-2009, 15:25
Tim, we were talking about proof but if you want to start a new thread about mingling I'll be happy to add to the dialog.

barturtle
03-26-2009, 15:29
Tim, I don't ask personal questions nor do I answer them.

The point was that making blanket statements such as that can lead to the spreading of inaccurate information. If you or I or Jimmy Russell make a statement such as that and don't give a "but sometimes" or "not always" or "for the most part", some people will be lead to believe that there are no exceptions to the rule.

barturtle
03-26-2009, 15:32
Tim, we were talking about proof but if you want to start a new thread about mingling I'll be happy to add to the dialog.

The point was that those whiskies from that one area may have all dropped in proof, so your "Master Distillers mingle barrels from upper and lower floors/racks/ricks and the resulting whiskey will be higher in proof than it was when first entering the barrel." statement is not always correct, and therefore a mingling could be lower in proof than what it was when it entered into the barrel.

squire
03-26-2009, 15:40
Tim I can't speak about what Mr. Jimmy might say, though I certainly defer to him regarding Bourbon, but I won't quote him or any of the other Masters I have had the pleasure to meet over the years because I only post first hand.

squire
03-26-2009, 15:42
And I don't post to the lowest common denominator of readers.

barturtle
03-26-2009, 15:48
And I don't post to the lowest common denominator of readers.

Well, I will. After all, we are in the "New to Straightbourbon' section. I believe it is important to take the time and explain things in terms that as many people as possible can understand. I try to be both student and teacher in all endeavors.

squire
03-26-2009, 17:10
Tim, new means introduction, straight forward information is best.

barturtle
03-27-2009, 00:12
Tim, new means introduction, straight forward information is best.

I don't believe that straight forward information has to be an inaccurate, gross simplification.

...and it's Timothy.

squire
03-27-2009, 05:57
And you can call me Doctor. Nah, don't bother, I dislike being formal during my off time.

Bourbon Geek
03-28-2009, 06:52
Ok guys ... and gals ... Here's the Chemical Engineer's take on whiskey proof in the barrel ...

1. Oak, as it turns out IS a semi-permeable membrane ... simply put, what passes thru the membrane is dictated by a number of characteristics ... chief among these are the relative vapor pressures of the barrel constituents on BOTH sides of the membrane ... ie inside and outside of the barrel. Nature wants to make things more equal ...

2. Vapor pressure is dictated by relative concentrations of the constituent parts as well as by things that effect their tendancy to evaporate ... like molecule size, relative polarity of the molecules, etc.

3. The nature of the membane can also effect the rate of passage of certain molecules through it ... like pore size and polarity ...

4. As a result of the foregoing, water IS predisposed to pass thru an oaken barrel faster than alcohol primarily because of its much smaller molecular size ... (compare molecular weights for a rough idea here ... water is 18 while ethanol is 46) ...

5. The principal driving forces during maturation are temperature and humdity. Raising temperature causes evaporation inside the barrel ... which raises the pressure inside the barrel ... which drives the "preferred" molecules out. The concentration of the substances inside the barrel is relatively fixed ... compared with the outside conditions. As the humidity raises, the concentration of water outside the barrel goes up. Eventually, there is "enough" water outside the barrel, and ethanol will preferentially move across the membrane to make the outside concentrations more equal to the inside.

6. Similarly, dropping the temperature in a humid environment could actually cause the water to penetrate back in to the barrel.

7. Now back to whiskey. With bourbon, the warehouses tend to be far less humid (and warmer in the summer) than those for aging scotch, brandy, Canadian, etc. Hence, it is generally accepted that proof goes up during bourbon maturation, but down for virtually all of the others.

8. While all of that is true on a macro level, there can be differences within a single bourbon maturation warehouse. Since things tend to be more humid at lower levels of the warehouse (since water vapor likes to sink in air) ... and far less humid at the top. Take a theoretical 7 story warehouse aging a theoretical bourbon for ... say ... 10 years ... If you fill 3 identical barrels with 125 proof new make bourbon and put one in the rafters on the 7th floor, one in the bottom rick on the first floor, and one in the center rick of the 4th floor of an otherwise full maturation warehouse ... when you come back in 10 years (maybe less) the one in the middle will still be near 125 proof ... maybe a tad more. The one on the bottom will be closer to 110 proof, and the one in the rafters will be approaching 140 proof.

Hope this helps

Squash
03-28-2009, 07:02
Thanks Bourbon Geek. I had given up.

kickert
03-28-2009, 07:04
Thanks Geek.

sounds very similar to the answers given before the pissing match.

barturtle
03-28-2009, 08:20
Thanks, Dave. Number 5 satisfies me.

squire
03-28-2009, 08:51
Another good post Dave, I actually understood most of it. If I could direct you back to barrels for a moment, perhaps a new thread might be better, I would like your thoughts on the wood itself, density, porosity, maturity of the tree, stuff like that and how it affects aging and/or flavor of the whiskey.

smokinjoe
03-28-2009, 08:59
I just noticed that the original poster, Jackie, hasn't been on since about post #3. Ain't he gonna be surprised. After wading through the 5 pages of follow-ups, I wonder if he ever posts again. :D Now, that was a good "bang for your buck" first post!
:toast: to you, Jackie.

squire
03-28-2009, 09:38
Your right Joe, we either scared or encouraged him.

Bourbon Geek
03-28-2009, 12:50
Another good post Dave, I actually understood most of it. If I could direct you back to barrels for a moment, perhaps a new thread might be better, I would like your thoughts on the wood itself, density, porosity, maturity of the tree, stuff like that and how it affects aging and/or flavor of the whiskey.


Squire, Books have been written on less than this ... If you start a new thread and narrow it down a bit, I'd be glad to chime in ...

squire
03-28-2009, 15:46
You're correct Dave, I've read a few, but that was decades back. I was thinking some introductory information might be of use on this 'intro' forum.