The science of thawing alcoholic drinks - how does vodka thaw?
November 29, 2005 4:12 PM   Subscribe

Does thawing vodka decrease in alcohol content as it thaws?

My fridge's freezer is pretty decent, as it can freeze solid my 40% alcohol (that makes it 80% proof) Smirnoff vodka.

The bottle's icey contents always start to thaw rather quickly, but after a while, when most of it is pourable, there will be content frozen against the inside walls of the bottle that defrosts a lot slower than the rest. For a full bottle, this would be an estimated 20-30 volume percent.

Am I right to assume that what is left frozen, has less percentage alcohol content than the pourable part?

There is a significant time difference in defrosting part 1 (quickly pourable) and part 2 (stays frozen long) of the bottle content.

This would mean I am serving maybe 100, 120 or more % proof to my guests.

Interesting, but for some unwanted.

Does anyone have any evidence of this? (Drunken friends, wrecked cars, illegitimate children all count).
posted by Grensgeval to Food & Drink (8 answers total)
Do you leave the bottle open as it thaws?
posted by interrobang at 4:18 PM on November 29, 2005

Pure ethanol has a freezing point of -114 degrees Centigrade compared to pure water's zero.

You have a mix of the two (40% ethanol) and have to do some physical chemistry to figure out the composition of what you are getting.
posted by NucleophilicAttack at 4:42 PM on November 29, 2005

Best answer: Check out apple jack making, or this page on freeze distilling, for an explanation of what you are likely seeing. What's freezing first should be relatively pure water, so I'd guess you're closer to 180 proof if you time things right.
posted by nomisxid at 4:46 PM on November 29, 2005

the melting (freezing) point of ethanol is -114 degrees C, or -173 degrees F.

see this page which includes calculations of freezing points for various mixtures of water and EtOH.

i suspect what's happening is that water somehow phase separates when you put it in the freezer and forms ice on the inner surface of the bottle. this would increase the alcohol content of the remaining liquid. my thermodynamics is rusty, but i suspect the reason this happens has to do with how rapidly you cool the bottle - i think that slowly lowering the temperature would cause a more homogeneous behavior.

anyway, i think the answer to your question is yes, the liquid in the middle should have a greater alcohol content.

as experiment is the best judge of a scientific hypothesis, the best thing you could do would be to pour off some of the quickly-melting stuff and measure its density, or specific gravity. one way is to carefully measure the volume and weight, then divide; another (cheap) way to do it would be to make a hydrometer and measure it directly.
posted by sergeant sandwich at 4:46 PM on November 29, 2005

You're right.

Well, the vodka doesn't decrease in alcohol content but it does decrease in alcohol percentage (which is what you mean hear, I think). Alcohol freezes at a much colder temperature than water, and it melts much more quickly. If you pour only a few minutes after taking the bottle out, you may be giving your guests near 100% (200 proof) vodka.

When Someone Who Is Not Me used to brew their own, they once used 'freeze distilling' to concentrate some of the brew. You do this by partially freezing the product and dumping the frozen parts (mainly water) out.

On preview, see nomisxid's link for freeze distilling
posted by atrazine at 4:47 PM on November 29, 2005

I think the idea of freeze distilling is similar to fractional crystallization. It works with other solutions as well - I remember using it to pass the "sludge test" (which I can't find a good link for . . . basically we had to identify what chemicals were mixed up in a jar we were given) in 8th grade chemistry.
posted by aladfar at 9:20 PM on November 29, 2005

Sweet mother of jesus... according to sergeant sandwich's link, 80 proof vodka freezes at -26.95C... why the hell do you have your freezer turned up to be -26.95C?? I hope you're not paying electricity bills where you live... hehehe

But as everyone has said, to get back on topic, the bits that are thawing first would be higher in alcohol percentage for sure.
posted by antifuse at 1:37 AM on November 30, 2005

A quick and easy way to check would be to try to burn it. But, um, be very careful. Pure Ethenol packs almost as much punch as gasoline.
posted by delmoi at 9:02 AM on November 30, 2005

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