This is a one fermentation vinegar. To make it you will need...
Ingredients:
- 1.25 liters of whiskey
- Unpasteurized Vinegar
Equipment:
- 1 Large Pot
- 1 Mason Jar
- Cheese cloth
- 1 Aeretor, with a tube and rock.
Procedure
Summarized: Start by burning the alcohol off of one liter of whiskey (leaving the extra 250 ml on the side). Once the flames have ceased and the alcohol has burned, add enough water the bring the volume back to one liter. This liter of non alcoholic whisky-smelling liquid gets added the set aside whiskey and back-slopped with 300 ml of unpasteurized vinegar.
Step by step
Start off by heating up the pot by itself. You do not want it to smoke but to be hot enough so that a reaction starts immediately. Pour the whiskey in the pot in batches, not all in one go. How much you add will depend on the size of the pot. As I was using a big one I did two batches.
Ideally, the whiskey should ignite when it hits the hot pot, this however, like in my case, will not always happen. If you find yourself in this situation light it up using source of fire, a long gas lighter will be one of the best options.
Safety precautions!
If done carelessly, you can either burn something or get burned. To avoid any of that, keep the following
in mind:
- Make sure you are in an open space, or a space that presents low risk of burning: I did it in
enclosed space but there was nothing around that would easily catch on fire.
- If you are doing this at home, in your kitchen, make sure the extractor fan is clean; these fans have a
tendency to accumulate fat, a very flammable material.
- If you must "manually" ignite the Whiskey, do not do it right after adding it to the pot. Let some of the alcohol evaporate for 30 seconds to a minute and then ignite. If you do it immediately you will get a huge flame. Keep your head and body away from the pot.
- Keep the lid if the pot with you; if at any given point you feel uncomfortable by the size of the flame
cover the pot with it and turn the fire off, the flames will eventually cease. If you wish to continue,
simply restart the process.
With these precautions I do not mean to scare you but to inform you so you can make educated choices.
Watch the following videos to see my burning alcohol off experience.
The waiting period was edited out but it was about ten minutes long. In the video you can see my surprise to the lack of immediate appearance of the flames (meaning I could have probably warmed the pot more) so I ended up using a regular lighter.
The flames can get pretty big.
At some point I started feeling a little shaky about the flame size. The lack of stability of following video leaves that pretty clear.
I added the second batch of whiskey (not on video) when the flames started to get smaller. I kept the process going until the flames had disappeared. By the time this had happened about half of the original volume of whiskey had burned off. To this resultant liquid I added enough water to bring it up to a liter.
Add 25% of fresh whiskey and 30% of unpasteurized vinegar. Pour the mix in a mason jar, place the airstone at the bottom, cover the top with cheesecloth and hold with a rubber band.
The mixture was left to oxidize for ten days. When we mixture was not getting agitated the solids came together at the bottom. 
Taste
After the ten days the vinegar was not particularly acid; it was so smooth that it was straight up drinkable. The vinegar I use to back-slop was a apple-honey unpasteurized one, the sweetness coming from it balanced the acidity and created a round flavor and very enjoyable flavor. I pasteurized a few bottles and bottled the vinegar in smaller containers to have those sitting and getting even rounder.
So I allowed the vinegar to sit, hoping for the flavors to come together. It first started coming together even more, but then an acetone smell appeared... This acetone smell caught me very off guard, so I went back to reasearching. Turns out that if theres alcohol that did not turn into acetic acid, it will then start smelling similarly to acetone.
"So the acetone smell is what happens when the reaction to make vinegar isn’t completely finished. Many bacteria just make acetaldehyde and then start creating the pungent odor. The reasons for incomplete reactions can vary but the top two are lack of air (oxygen) and too much alcohol in the starting mash." Source
"If your vinegar smells like nail polish remover, you know it’s still actively working. When it smells like vinegar instead, it’s ready." Source
So! my vinegar was not ready! Looking back now, the low acidity was probably a major indicator for it needing more time but, being an amateur brewer, I simply assumed that was how it was meant to be. I put the aerator back in and let it sit with it for a few more days to see if then it would finish oxidizing.