Listening to an episode of Basic Brewing last night, I heard a guest say that most of the conversion in the mash happens in the first half, and that the mash can thus be cut down as short at 45 minutes.

It seems to me that this would work, especially if you're doing a mini-mash for flavor and it's not life-or-death whether you get the exact right efficiency to hit your target gravity.

What's the lower limit here?

  • I'll come back and edit this when I do some tests. Apr 23, 2010 at 1:04

2 Answers 2


You need to ask yourself "Minimum mash time for what?" You can get pretty full conversion in about 20-25 min. A recent experiment on Basic Brewing Radio concluded that a beer mash for 45 min. was better tasting than one mashed for 20, and a beer mashed for 60 was better than one mashed for 45. For maximum fermentability, a 90 min. (or longer) mash works better. So when you ask what the minimum is, you have to take into account the results you want to achieve.


I don't under stand the second part of the question, so I'll speak to the first.

I have heard estimates as early as 20minutes in the mash is converted. Its a function of temperature too. So of you are mashing at 158F it goes faster than if you are mashing at 149F. Of course, trying to do a quick mash at 158F is fine if you are doing something that works with a lot of body.

I'd like to see this explored more on the homebrew level. But it requires brewers to be checking for completeness with an iodine test.

  • I think the iodine test is the key to everything. Try whatever technique/mash schedule you like, but only the iodine test can tell you whether your sugars are fully converted. Apr 22, 2010 at 17:24
  • Clarified the question and ordered some iodine strips. What the heck, right? I'll try science. Apr 22, 2010 at 19:07
  • True that it isn't life or death, but you don't want to be adding too much starch to your beer due to a lack of conversion. Starch is a prime source of food for your undesirable microbes.
    – brewchez
    Apr 22, 2010 at 19:15
  • Betadine works fine, too. I'll use that. Apr 22, 2010 at 19:45
  • The iodine test can be wrong as often as it is right. In addition, it won't tell you what kind of wort you're producing. I advise new brewers to try the iodine test once for fun, then forget it exists.
    – Denny Conn
    Feb 22, 2011 at 22:15

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