Jeff

Alcohol is hydroscopic (absorbs moisture from the air). Your 99% will
go down to 91% if you leave the bottle open. Fortunately, it takes
some time so you don't need to be fanatical about replacing the cover.
https://en.wikipedia.org/wiki/Azeotrope
Note that 70% alcohol is what you want for a disinfectant because some
water is needed to kill of hydrophylic bugs.

I should probably buy some 99% alcohol for lens cleaning, but have
been getting away with using the 91% stuff without streaking.

http://www.ebay.com/sch/i.html?_nkw=99%25+alcohol
Ugh... about $8/pint



Wouldn't have guessed Alcohol is hydroscopic. Or that water in 70% is needed to make the bugs go belly up (or blow up).

I was thinking of asking on Freecycle for a thimbleful, if I decide I need it. I'd certainly offer if I'd bought a pricey bottle and someone asked.