I have been feeding my sourdough starter daily for just over two weeks and everything is constantly going wrong. At first water was sitting on the top, then it started smelling of nail varnish, and now it has a green mould at the top. Should I just give up and throw it in the bin?

  • 3
    dark water sitting on top? That's hooch, maybe your starter needs to be fed more or more often.
    – Luciano
    Mar 30, 2020 at 12:25
  • 1
    related cooking.stackexchange.com/questions/100337/…
    – Luciano
    Mar 30, 2020 at 12:29
  • Mould is the only thing in my experience that makes a sourdough starter unrecoverable. The spores can persist so, as mentioned in aucperia's answer below, you need to thoroughly clean the container. Also if you keep the starter in the fridge, check for mould there: I had two healthy starters go mouldy before I realised the fridge was well in need of a clean. Mar 31, 2020 at 10:01

3 Answers 3


If it has mold on it then it needs to be thrown away, you are unlikely to salvage it. Once a sourdough starter goes wrong it's generally not worth your time to try and save it, just start over.

  • 5
    If you reuse the same container, be sure to fully sanitize first. Those spores can linger and reinfect.
    – dlb
    Mar 30, 2020 at 16:38
  • 1
    That's a good point @dlb, in fact cleaning the container before you use it is very good policy.
    – GdD
    Mar 30, 2020 at 16:53

As others have said, if it's mouldy throw it out and start again. These hints might help you be more successful next time:

  • thoroughly clean and sanitise the jar and all the implements (spoons etc) before use by boiling. Wash your hands before you start making the starter and before feeding
  • feed every day (as you have), and stir well. The starter needs oxygen as well as food and water; a good stir can help with this. Nail varnish remover (acetone) smells can indicate inadequate feeding or inadequate air. You should be removing 20-25% of the starter and replacing it with fresh flour+water each day
  • protect from flies, dust, etc with a loose-fitting lid (a tight lid is a recipe for explosions)
  • watch the temperature. When starting off, warm temps are generally best (20-25°C) but if you are having trouble you could try cooler or even warmer (airing cupboard)
  • a week should be enough to get the starter going. After it is bubbling well, I move mine to the top of the fridge door. This means I can get away with feeding it less often. If you keep it warm after it's got going it will need a lot of feeding - 20% of its weight every day - and you will end up with huge amounts of starter!
  • if all else fails, try a different flour. Organic rye flour is recommended, but even just trying a different brand could help.

It sounds like:

  1. you are not feeding it often enough OR
  2. you are not discarding enough (you should take a small amount of starter, mix with >5x as much feed, discard the rest) OR
  3. you are not changing the glass/jar when performing operation b

or any combination of the above.

I keep around 50-100 grammes in my jar. I try to freshen it every week. When i fresh it up I take 2 table spoons of the starter, put 50-100 grammes of 1:1 flour/water, mix well, check that it starts, discard the old glass contents and put the new one back in the fridge. In a new glass

If I bake with it, I do a freshen routine, but add more feed so that it is ~250grammes which I then use as soon as it has risen to what I think is the top - but I take a little bit off and put back in the fridge (in a new glass)

I rotate around 2-3 glasses, of which I have way too many on account of saving every lidded glass of whatever.

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