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Hi All! I tried to make a sourdough starter, and after 24 hours I uncovered it and discovered black spots and 2 white fluffy areas. The black spots are only at the top layer so can I still use it after removing this layer?

  • The white fluffy area look like un-mixed flour. What are the ingredients in your starter?
    – moscafj
    Commented Jun 16, 2018 at 10:56
  • I used white flour & water. I remember thoroughly mixing everything until the mixture was smooth so it is unlikely to be un-mixed flour.
    – user3721
    Commented Jun 16, 2018 at 11:16
  • You say you uncovered it after 24 hours, how did you have it covered? I ask because the surface looks very dry and crusted in a way I never experienced with my starter.
    – Spagirl
    Commented Jun 16, 2018 at 14:17
  • I covered it with a thin folded ikea tea towel. Then I used an elastic band to secure the towel to the bowl. Could the dry surface be because the humidity is low in Australia?
    – user3721
    Commented Jun 16, 2018 at 14:48
  • @user3721 I’d guess so. If you try again I’d suggest covering with a plastic film or at least a plate to keep the humidity higher in the bowl.
    – Spagirl
    Commented Jun 16, 2018 at 15:36

1 Answer 1


I would discard this batch, carefully clean everything and start over.

If you truly mixed well in the beginning, then the fluffy bits are probably mold and the black spots are somewhat fishy as well. After only 24 hours, you won’t have a strong culture going under that top layer and the mold problem will likely continue. Remember that a sourdough means that the desired yeasts and bacteria grew faster than the unwanted ones and that they create an environment where they can outcompete possible intruders. While a mature starter with problems can be salvaged by using just a bit from an unaffected area, this is not true for fresh flour and water mixes.

If you start over now, you won’t have lost much: a day and a cup of flour perhaps?

Not part of your question but perhaps helpful:
The amount of yeasts is greatest on wholegrain flour - it may be worth it to get a small bag from your local organic store. For upkeep / later feeding, white flour is fine.

  • 1
    I would discard the batch as it is probable there is much more contamination that you just don't see. It is far to risky. I would also discard all remaining quantities of ALL the ingredients you used (though I've a strong suspicion that the contamination is in the flour) I've bought flour that was well before the expiration and found the bag crawling with weevils just a short time after I opened the bag)
    – Cynetta
    Commented Jun 16, 2018 at 14:51
  • Wholegrain is often not needed, but I also tried to get going in low humidity and had trouble. I added a bit of wholegrain rye and that did the trick and got thing activated much faster and going. I am not fond of the taste of rye in some of the things I make with it, but as soon as the sourdough got going right, the rye was diluted out from normal feedings. It just kick started the yeasts and local bacteria. From others, it seems like any whole grain can do the trick though. The bran I believe is likely to have the initial boost of captured yeasts.
    – dlb
    Commented Jun 18, 2018 at 14:17

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