Geeky Question on Aging & Proof

[Cranecreek]

Thought I would pose this to the community:

 

Federal law limits bourbon to be "Oaked" not exceeding 125 proof.  Using the 125 number, a barrel of bourbon would therefore be about 63% alcohol and 37% water by ABV. Correct ?  Now lets assume that barrel is aged for say 8 years.  During that time the Angels Share (evaporation) would affect both the water and the alcohol, BUT- since alcohol evaporates more quickly than water, would not there then be a drop in alcohol as a percentage ?

  Using a bottle of ECBP C917 as an example (which HH does use the 125 entry proof for) it's proof is 131.0.  So how is it possible that the proof actually increases rather than decreases ?

  I have not found an answer and thought one of you may know.

[Jav]

I think it matters where the barrel is aged.  Certain temperatures and conditions can cause the water to evaporate quicker than the alcohol, and other conditions cause the opposite.  I am by no means an expert, but I would think that alcohol evaporating quicker would be more common.

[Jav]

This looks interesting:

http://www.whiskeyprof.com/water-and-alcohol-molecules-and-barrels/

[Cranecreek]

5 minutes ago, Jav said:

This looks interesting:

http://www.whiskeyprof.com/water-and-alcohol-molecules-and-barrels/

That  Jav is exactly what I was looking for !!  Explains alot.  I was thinking it might have a  molecular explanation.  Thanks!

[Cranecreek]

It makes you have to marvel at the challenges of aging a bourbon like George T. Stagg (another 130 proofer) for 15 years plus.

 

Location ! Location ! Location !

[Jav]

Yeah, truly fascinating.  I would love to visit some bourbon making locations!

[Old Hippie]

great article! As he alluded to, relative humidity factors in as well. When they age rum in the Caribbean they  top the barrels off as they lose a lot of alcohol. The air is already saturated with water so they lose alcohol.  

[jbutler]

7 hours ago, Cranecreek said:

Thought I would pose this to the community:

 

Federal law limits bourbon to be "Oaked" not exceeding 125 proof.  Using the 125 number, a barrel of bourbon would therefore be about 63% alcohol and 37% water by ABV. Correct ?  Now lets assume that barrel is aged for say 8 years.  During that time the Angels Share (evaporation) would affect both the water and the alcohol, BUT- since alcohol evaporates more quickly than water, would not there then be a drop in alcohol as a percentage ?

  Using a bottle of ECBP C917 as an example (which HH does use the 125 entry proof for) it's proof is 131.0.  So how is it possible that the proof actually increases rather than decreases ?

  I have not found an answer and thought one of you may know.

This topic has been discussed here repeatedly and in depth over the last couple decades. Use the search, and it will return all manner of interesting stuff -- like this thread. The thread is interesting on a few different levels!

[Cranecreek]

12 hours ago, jbutler said:

This topic has been discussed here repeatedly and in depth over the last couple decades. Use the search, and it will return all manner of interesting stuff -- like this thread. The thread is interesting on a few different levels! 

That was not only informative to read but also quite entertaining !  

Edited May 4, 2018 by Cranecreek

[smokinjoe]

On 5/4/2018 at 7:48 AM, Cranecreek said:

That was not only informative to read but also quite entertaining !  

We can have our moments of snippiness!!  LOL

 

BTW, “bourbon geek” in there is Master Distiller Dave Pickerell.

Edited May 5, 2018 by smokinjoe

[Harry in WashDC]

15 hours ago, jbutler said:

This topic has been discussed here repeatedly and in depth over the last couple decades. Use the search, and it will return all manner of interesting stuff -- like this thread. The thread is interesting on a few different levels!

Thank you for pulling that up.  What a wonderful way to start the day - education that is entertaining as well.  EDIT - Yeah, I logged on while still in bed.  At least I don't drink before I get up.

Edited May 4, 2018 by Harry in WashDC

[Flyfish]

On 5/3/2018 at 11:49 AM, Jav said:

I think it matters where the barrel is aged.  Certain temperatures and conditions can cause the water to evaporate quicker than the alcohol, and other conditions cause the opposite.  I am by no means an expert, but I would think that alcohol evaporating quicker would be more common.

Nor am I an expert but you might want to take a look at the chemical formulae for alcohol and water. We usually assume that alcohol if more volatile and therefore more evaporative. Water, however, is a much smaller molecule and often escapes at a much higher rate. Thus, as the angels take their share, the volume of whiskey in the barrel goes down but the proof goes up. That is, the alcohol is still there but the poor angels' share is actually mostly water. There are probably SBers who can explain this more clearly and with greater authority.

[Cranecreek]

As was pointed out by "the Boss" this topic was discussed in depth in 2009.  This post by the Master Distiller at Makers Mark explains the phenomenon of proof rising during storage.

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Bourbon Geek

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Posted March 28, 2009

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

Edited May 5, 2018 by Cranecreek