Barrel Storage, humidity & alcohol

I heard a few things around the campfire that I wasn’t quite sure about.

1.) Does the humidity level in the barrel storage environment affect the amount of wine a barrel will soak up?

2.) If Q1 is true, is alcohol absorbed more/less/same ratio as the juice? Would humidity (high or low) assist in a barrels ability to soak up alcohol?

No expert I, but I don’t think barrels “soak-up” wine as much as they allow very small amounts of ozmotic action (think of them as a membrane); that is, air in, wine out. Hence, the term “Angel’s Share” and the need to top up.
Best, Jim

Also no expert, but had a similar discussion recently about bourbon barrels. The barrel will absorb liquid about 3/4 the way through the staves (a barrel must be “wet” to seal, a barrel of dried staves would leak all over!) and once equilibrium is achieved then osmosis can occur. In humid conditions, alcohol can go out, but in a hot dry barrel room in KY water evaporates, thus increasing the alcohol content.

Doesn’t really directly answer either of your questions, but gives you a little more info…

Very good answer, Brent.

Will, I remember hearing just recently in a seminar about how deep wine penetrates into staves based on where they have found Brett living, but my recall is shite. I want to say it was 8-10mm. Obviously, thin-stave barrels are 22mm thick, so wine must penetrate far less than that.

Brent is correct in that in more humid environs, the evaporation loss from barrels will include a proportion of ethanol to water that is higher than in wine and thus lower the alcohol content in the remaining wine. The opposite is true in dry environs. The data I have seen is that about 80% humidity evaporates 13% ethanol:water, meaning the wine % will remain constant.

On a related subject, do you know how far steam penetrates the staves when used to sterilize a barrel? I ask because I had heard that it went farther than brett can live - which is a good thing.
Best, Jim

Jim- I’m not sure about that. This may interest you, though:" onclick=";return false;

Ultra-sonics to sterilize barrels. Interesting. IIRC, you are very interested in the reduction of water use, too, correct?

No affiliation, blah, blah. Just something discussed a bit at this seminar.

Interesting. Particularly the part about “increasing” (preserving is what I think they mean) oak flavors. I’m guessing this isn’t as useful a method for someone who uses barrels from multiple years and thus limits the oakiness, to some extent.

In low humidity, the wine in a barrel will increase alcohol percentage. In a high enough humidity environment, the alcohol percentage will drop.


There was an article on ultrasound barrel cleaning in one of the wine magazines a year or two ago…maybe in Practical Winery & Vineyard? I remember the article stating that steam does not penetrate the staves far enough to guarantee killing all the brett that may be in there. Saw that ultrasound cleaning system vendor at the Unified Symposium in January…can’t recall how much their system runs but it ain’t cheap.

Its a jungle out there . . . I read something that said just the opposite.
Best, Jim

Not surprising to hear that, Jim…so much contradictory information out there on all sorts of things. Seems to me that if steam of whatever method you’re using now works for you, little reason to switch to something as expensive as ultrasound.