I've been doing research about making alcohol, and I can't find much involving how much alcohol wild yeast can produce before stopping. I'm just wanting to make pure alcohol and vinegar for chemistry reasons, so I'm not worried about taste. I want to use wild yeast more or less because I want to be able to do it that way. If you have one, please give me a source. Thanks for any help in advance. Also on a side note, is this a good resource for telling me how much sugar for a percentage of alcohol for a certain volume?


  • 1
    This is a bit like asking how fast a wild animal can run. It really depends on the animal. Without any specifics you're probably going to have to do some trial/error. It can also depend on how nutrient-rich whatever your pitching yeast into is. There's just too many unknowns to give you a definitive answer.
    – rob
    Commented Jan 4, 2022 at 13:34
  • I just wanted a very general answer, like 5%-10% or something.
    – brewer567
    Commented Jan 4, 2022 at 21:11

1 Answer 1


The problem with wild yeast (caught in the wild) is that it is not a single yeast, but a mix of yeasts and other organisms which consume sugar from a sugar solution and can create different outcomes, depending on the organism getting a hold first.

  • Moulds: spoilage
  • Candida: forms a film, but is not real a spoiler
  • Lactobacillus: lactic acid formation
  • Acetobacter: turns alcohol into vinegar when exposed to oxygen
  • Other bacteria can produce butyric acid, smells like barf
  • Sacharomyces yeasts: those that really turn sugar into alcohol
  • Brettanomyces: if you are lucky, these can turn sugars which are not fermented by ordinary yeasts also into alcohol, so you can get a higher ABV

I did once a test with a sourdough which smelled very yeasty (banana) and fermented some wort into beer. I got an attenuation of 70%.

Different strains of yeast will also have different alcohol tolerances.

So, you can't really predict what the ABV you will get from wild yeasts. You can be lucky, or not.

If you are prepared to work long term, you could prepare a couple of recipients of wort or juice, leave them overnight outside to catch wild yeast and then check what happens with them. If they ferment, measure the gravity and then start propagating from the most promising results.

  • I was planning on just trying a sugar wash. I should put cheese cloth over the recipient container, yes? I've heard you do that with sourdough.
    – brewer567
    Commented Jan 4, 2022 at 21:14
  • I'm just going to try that.
    – brewer567
    Commented Jan 4, 2022 at 23:28
  • @brewer567: Actually to catch the wild yeast you should not put a cheese cloth over it, but you should of course add something which keeps insects out. Here is a nice reference: beerandbrewing.com/spontaneity-prospecting-for-bugs And do you accept my answer? You can mark it like that.
    – chthon
    Commented Jan 5, 2022 at 6:34

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