"I've been making as close to single malt ""scotch"" as practical....meaning 10lbs malted barley and 7 lbs sugar. The first four batches turned out great, though smaller than normal yields cuz the barley soaks up a lot of liquid volume, meaning less vol to distill. Anyway, this last one was somewhat bizarre: I wanted a slow ferment so I kept it at 70 degrees, nothing happened until around 36 hr after I pitched the yeast. As I left for work that day it was lightly bubbling away, I'm thinking ok its cool temp so it will be slow. Get home from work that day and I find it volcanic and had shot up thru the bubbler airlock. There is wort on the floor and the top of the lid. That was around my 40th fermentation in close to 2 yrs in this hobby and never happened before. I clean up the outside and let it do its thing. It bubbles 2 more days and then stops. OK.
Been reading a lot about off flavors during distillation so I let this clear for 3 weeks as there are a lot of particulates in a barley wort. Day of distillation I siphon off the really clear beer looking stuff, smells great, taste it no sweetness at all and no vinegar taste, but also no alcohol taste. Distill it.....sat at 70 degrees for 2 hrs (propane)! This is wierd....then temp shoots up to 170 for about 3 minutes then 196. I collect 2 quarts and taste.....no alcohol, nada, zip. Shut it down. The stuff in the quarts smelled good and ""scotchy"" but turned out to be weird water.

Did some reading and I may have gotten a Lactobaccilus or Lactobacter infection. Apparently these bugs turn alcohol to lactic acid. Other than saying pay attention to sanitation I don't know what else. I thought I did but obviously not. Bummer, its a lot of work to make good scotch lol"