Effect of oak on specific gravity?

[Ballzac]

Sorry if this has been covered before. It seems like a pretty logical question that I thought would have been asked before, but can't find it using the FSE. I'm wondering roughly how much effect oak has on SG.I've had a couple of sticks of toasted french oak sitting in a rum for a month or so, and it's acquired quite a nice ruby hue, along with a subtle sweetness. The SG has gone up, but most of that time it has been in a demijohn with a cork, and although this allows for a little evaporation, I don't think it could account for 4% or so ABV. I diluted some supposedly to 40%, but it tastes a little stronger. There never seems to be a mention of the possibility of sugars from the oak raising the SG, and the increase in SG always seems to be put down to the 'angel's share'. Does anyone have any thoughts on this? Has anyone done a test with a completely sealed container with oak in the alcohol to see if the SG increases significantly?

[noobsauce]

Though i cant point you to a test....using some math and such i doubt that oak would change SG much if at all.

For example....put say a couple of sticks in...roughly 4 ounces (114 grams) im guessing. if it was in 1 gallon (roughly 4 liters) and the oak was 50% sugar (which we KNOW its not) it would only raise the SG by about 0.8% according to the HD calculator.

Even accounting for solids and such that might leech in i dont think it would change it that much..unless we were using sawdust...

Maybe some others have ideas that are better than mine?...

[Ballzac]

That's a very convincing argument. I am going to have to assume that it's mostly evaporation.

[Husker]

That's a very convincing argument. I am going to have to assume that it's mostly evaporation.

Thats the angels share, and you WANT it to evap. The most volatile will evap the fastest and most easily. Thus your acetone (if any were in there), methanol, ethyl acetate (and yes ethanol) will be some of the first things to evap. a 4% loss is not unheard of. If you had cork to allow air flow, it would lose the alcohols first. 4% drop in a month is a lot.

I also wonder if the oak is more likely to absorb the alcohols, than the water? I have no answer to THAT question.

H.

[airhill]

Guessing but I would suspect water would be absorbed more easily than ethanol as the water molecule is much smaller. Be surprised if it was 4% though.

[Ballzac]

Y'know, there's a chance I was just being a bit sloppy with measurement. Air bubbles stuck to the hydrometer. Rounding off temperature adjustments. Perhaps a quarter of a percent from sugars in the wood. A little bit from evaporation. It could easily add up. I honestly don't think that 4% is gone JUST from evaporation.

It doesn't really matter though. I started this thread more out of scientific interest in the effects of oak than because I was worried about where my alcohol had gone, lol.

[Hawke]

I start my oaking at around 65%, never really paid much attention to the SG as I was cutting it to drinking strength. Hmmmm

[Dnderhead]

I checked a sampel barrel of scotch/irish(10 gal) it has sit for 7-8 months ,went in at 60% and is still 60%
from what I read, dry weather you loose more water, damp weather more alcohol.