Let's see, I could mention my first batch, which was a grape concentrate that got an infection, but that isn't that interesting. But I think my greatest disaster may be an ongoing one:
My 2nd batch, since the first went so well, I thought I'd do something harder, so I tried a carrot wine. A buddy of mine has a juicer, and I bought a WHOLE LOT of carrots, so much so the cashier looked at me kinda funny.
We juiced the carrots, and ended up with about 1 1/2 gallons of carrot juice. I should have stopped there, but I filled with water up to 2 gallons. Not huge, but I watered it down. No grape concentrate or raisins added of course. So this was the first time using my hydrometer, and I got very confused about the reading, and ended up not putting enough sugar in, probably by a factor of 2.
Next, it was also my first time using the acid test kit, and as you can imagine, carrots are not very acidic. When I put all the 10 ccs of sodium hydroxide in the test container with the must and reagent without a color change, I should have thought, "I need to add acid to get a reading here probably". But I didn't, I just guessed in a panic, and way too low. Strike two.
Now, it actually fermented pretty well for the amount of sugar I added, and I measured it with the hydrometer as dry as a bone and racked it. However, I thought it tasted a little weird, weak and thin, but maybe that was normal.
Anyways, long story short I had to fix it with added alcohol and acid blend, and it still didn't taste great. No infection, just not very good. So I stabilized, then a week later racked it and sweetened it. Now this is just a bad wine, not necessarily a disaster:
When I bottled it, it was very still, and did not need any degassing. I kept the bottles upright for 3 days, then put them in a rack.
Fast forward a month and a half to this morning. I noticed one of the corks was sticking about a quarter of the way out. Odd since I look at these bottles all the time, and yesterday it wasn't like that. So I take it out of the rack and turn it upright on the counter. When I get home I put it in the refrigerator and let it cool, figuring I'd try it before I pour it out.
When I open the bottle, it's like a champagne, very bubbly and oddly, much better! This would probably be good if I intended to make a champagne, but I did not. I took the rest of the bottles (corks all still normal), to the basement just in case, but I figure I may be looking at a disaster.
I'm lucky it happened as it did, and it didn't explode on my kitchen counter.
Weird that it suddenly started fermenting again. I used the recommended amount of potassium sorbate to stabilize, and waited before sweetening.