Distilled water is the best to use....when in doubt, buy the bottled stuff at wal mart in the gallon jugs...or if you have a water purification system...like say from the fridge, that will work too. PUR pitchers are great as well, and measuring is easy.

Shawn, that stuff is 100% Methanol with a blue dye like washer fluid, but you can also get it in clear that's by the gallon. It's a little high, at $2 a bottle, but it's readily available to me at my work, so I go ahead and use it.