Yesterday I made a batch of dough for a bread-like treat. It was a mix of cooled-off mashed potatoes, flour, instant yeast, room-temperature milk and room-temperature water.

According to the recipe it should rise in a warm place for about 30 minutes. So I placed it near a window with a hot towel on top for about an hour in the end, but nothing at all happened. I tried baking some of the resulting dough anyway, but it was not working at all.

So after that I gave up, turned down the central heating and went to bed a bit disheartened. I left the dough on the counter, in an open bowl. When I came back this morning, the dough had risen to at least twice it's original size, maybe more.

How come the dough rose to such a size overnight and what should I change to make it happen in minutes instead of hours? Am I underestimating what a "warm" environment is? (The house is usually at around 20C and the radiators are usually off, is that too low?)

And if the dough rises slowly and openly like this, is it still okay? I'm planning to try and bake it again when I get home from work, but it'll have been in the open for close to 24 hours then.

  • I don't think we have an exact duplicate on this question. But we have discussed the topic of bread rising speed many times before. You will probably learn a lot by looking into these older questions until you wait for somebody to write an answer. I don't know what the best search query may be, maybe "rising speed" or "slow rise" or "retardation", and separately "yeast temperature". Also take the opportunity to look at the questions listed as related to those you found (the ones on your question don't look promising).
    – rumtscho
    Commented Jun 10, 2015 at 15:24
  • related : cooking.stackexchange.com/q/42026/67 ; cooking.stackexchange.com/q/1513/67
    – Joe
    Commented Jun 10, 2015 at 19:06
  • Here is one of the most thorough answers we have on dough rising speed, the question is even a partial duplicate: cooking.stackexchange.com/a/44755/4638
    – rumtscho
    Commented Jun 11, 2015 at 8:28

1 Answer 1


There are so many factors in the rising of bread, have a look at this previous answer for something more exhaustive. I will say that 30 minutes is pretty short, especially when you are starting from a cool dough. You are using milk, which will enrich the dough, and although you haven't mentioned it I'm sure there is salt in the mix, both of these will slow yeast development.

There's nothing wrong with this, in fact slower is better for good gluten and flavor development. I would be prepared to let an enriched potato dough prove at least 3-4 hours, or overnight in the refrigerator.

24 hours may be too much at it may have over-proofed, also foodborne illnesses may have developed in that time. Personally I'd discard it and try again.

  • 3
    There is no food safety risk involved in long-proofed dough. Bakeries have been keeping sourdough starters for centuries and nobody shuts them down. Unlike other foods, fermented foods don't give you food poisoning, because the organisms in them can outcompete new bacteria at room temperature. Getting undesirable organisms in them is very seldom, they are mostly molds (well visible) and doesn't happen under usual storage conditions.
    – rumtscho
    Commented Jun 10, 2015 at 15:36
  • Ordinarily I'd agree, my caution is because the poster does not know how long it took for the yeast to get going.
    – GdD
    Commented Jun 11, 2015 at 7:54
  • I see. Interesting thought, but I think it's no reason for worry. First, actual bacteria growth speed is just as dependent on temperature as yeast growth speed, they don't start growing like crazy at 4 C, the danger zone is intentionally oversimplified because normally, you don't have an indicator of the speed of microbiological activity in your food (but in yeast dough, you have it - the rising speed). Second, a healthy yeast colony outcompetes bacteria, filling up their ecological niche, so even if they had an initial burst, they will be decimated by the time the dough has risen.
    – rumtscho
    Commented Jun 11, 2015 at 8:24

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