> The received wisdom is that hot whiskey expands into the wood, then when
> it cools it contracts, coming back into the barrel with lots of wood goodies
> for all the little whiskeys that didn't get to go into the wood.
I've heard that story, too, but I've seen absolutely nothing in the
technical literature to support it.
Studies of whiskey aged at constant temperature show that all the same
processes are happening, and all the same goodies turn up, just like in
"real", warehouse aged, variable temperature whiskey.
Piggott's book cites a Scotch study (Duncan and Philip J. Sci. Food
and Agric. 1966 17:208-214) showing that barrels that in a room with
fluctuating temperature and humidity were no different than barrels
at constant temperature and humidity, other than a small change
in proof. Storage temperature (fluctuating or not) had a huge effect
on all the non-volatile components of the whisky.
George Reazin of Joseph E. Seagram and Sons, Louisville, KY, published
a paper called "Chemical mechanisms of whiskey maturation" (Am. J. Enol.
Vitic. 1981 32:4 283-289) that doesn't even mention temperature variation!
Toward the end, he says "...it appears that temperature merely determines
the rate at which the various physical and chemical reactions proceed. It
should be pointed out that, although the various reactions occurring
during maturation can be increased with temperature, there does exist
an optimum temperature to produce the desired product quality. This is
because the organoleptic impact differs for each of the congeners. Thus,
as the temperature increases, the relative amounts of congeners present
change causing differences in the product quality."
> Is what you're saying that the whiskey isn't going to get any further
> into the wood no matter how hot it gets and it isn't withdrawing from
> the wood no matter how cold it gets.
Wood might be able to soak up more whiskey at higher temperature. I dunno.
You're still losing the angel's share at lower temperatures, so the whiskey
hasn't left the wood entirely! It's still going into the wood from the
inside of the barrel and exiting the wood on the outside! I guess the
rate will really slow down at really low temperatures, but I'd say the
wood never truly dries out.
I can accept that wood has more whiskey in it when it's hot and
less in it when it's cold, but the whole pulls-the-sugars-out-as-it-recedes
thing just doesn't jive with me. And the data don't support it at all.
> The variables are time in wood and average temperature, as the solvents
> become more effective the hotter it gets.
Time, temperature, and proof are the big variables. And the condition of
the barrel, of course (i.e. level of char, seasoning of the wood, &c.).
The chemistry of aging is much more complex and exciting than just being
a better solvent at higher temperature... the whiskey is acutally undergoing
chemical reactions with the wood. The wood is degrading... large, insoluble
molecules are broken down into smaller, soluble molecules. All kinds of
other stuff, too.
A lot of people say "average temperature", but I'd like to stay away from
that term... if you burn the turkey, you can stick it in the freezer for a
week in order to lower the "average temperature", but you've still burned
the turkey! There's not really a great term for it other than "time at
temperature", i.e. some time at high temperature and some time at low
I've noticed that the recieved wisdom is that, with heated warehouses,
you can get "an extra season" by heating during the winter. Why just
one? Why not heat up for the first two weeks of December and the last
two weeks of January? Wouldn't that give you two summers worth of cycling?
Why not go to three or four? You could age twelve years worth in three
I think that if cycling has any effect, the real effect is in oxidation...
if you take a barrel and bring it up to the top of the warehouse, it'll
hiss and whease... the air inside has heated up, therefore built up
pressure. Daily and/or seasonal variation might create pressure/vacuum
in the barrel that might puch out or draw in air. Or maybe not... maybe
the barrels are tight enough that water/ethanol/etc will evaporate to make
up the pressure difference.
If you talk to the beekeepers, they put the hives in the sun. That way,
the bees wake up earlier in the morning, and get more warm time to get
things done. Whiskey's probably the same way. Put it in an iron-clad
warehouse so it can warm up and wake up in the morning, and it'll get more
done that day.