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I've just started making my first brew, and am using vodka in the airlock, but am hoping for some more detailed info about what is best practice, or if there is not really any difference between using water, vodka, or other things I haven't thought or heard of...
Also, does the quality of the vodka count? (As in, cheap vodka has a, er, particular taste - if that ends up in the fermenter, how much will it affect the brew taste?)

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"Does the quality of the vodka count?" - Yes, but only for making Lambics, in which case you MUST use the "Grey Geuze" brand vodka. – Graham Apr 22 '13 at 17:08
up vote 7 down vote accepted

You can use water, vodka or starsan.

The purpose of the liquid in the airlock is to prevent gas transfer into the carboy, keeping out floating contaminants, like bacteria and wild yeast, and to also provide a deterrent for bugs like fruit flies.

If you don't overfill the airlock, then there is no chance of suckback. But if you want to be cautious, then using vodka or starsan will ensure nothing contaminated enters the beer if the liquid is sucked back into the carboy.

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thanks, I may have overfilled my airlock (in my excitement), but at least I know using vodka a) won't affect flavour and b) is now potentially better because of possible "suckback" :) – baldric Apr 8 '13 at 20:12

I personally use the starsan sanitizer that's left over from brewing that day, However, its just an extra precaution to kill anything that MAY get in the airlock. Vodka is the same principal, but relying on alcohol to do the killing.

That being said, cheap vs expensive vodka doesn't matter in regards to airlocking.

If it gets pulled into your brew there would most likely be no discernible change in flavor being as its such a small amount of liquid anyhow.

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I also use StarSan. The main reason not to use water is that it may getting sucked down into the beer if the beer's temperature drops enough to create negative pressure. Any contaminates in the water will get into your beer, possibly infecting it. Also a good reason not to use a sanitizer like bleach. – Tobias Patton Apr 8 '13 at 20:09
It would be nice to know if starsan can be effective after a few weeks. – Paolo Apr 10 '13 at 13:24
StarSan can stay good for a long time (years in my experience) if mixed with distilled water. – Denny Conn Apr 20 '13 at 21:59
I've heard anecdotally that if your StarSan solution gets cloudy, its no longer good. I guess you can just measure it with pH strips if you are unsure. – Graham Apr 22 '13 at 17:06
It's acid, if it's going to neutralize, it needs to see some base... – Travis Apr 28 '13 at 23:35

I use sanitizer in the primary and vodka in the secondary because I've never gotten an answer I trust regarding how long sanitizer is good for. I do know vodka kills bugs indefinitely. It's worked for me thus far.

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I use StarSan. My water's a bit hard, so my StarSan turns cloudy fairly quickly if I use tap water to make it. I make a small batch of StarSan using a gallon jug of distilled water, as mentioned by other posters, for long-term storage (spray bottles, filling airlocks)

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