I am finding it difficult to set aside enough time for a full brew day and have therefore wondered if it is possible for me to split up the process to two separate occasions.

The plan is for the two occasions to be with a week's interval.

My plan is as follows;

Day 1

  • Heat water
  • 60 min mash
  • Bring wort to boiling (?)
  • Transfer hot wort to carboy

Day 2

  • Bring wort to boil
  • 60 min boil with hops
  • Cool and ferment

Is it reasonable to do this without getting a contaminated beer? Will I have to bring the wort to boiling during my first day or can I just dunk it into a clean carboy directly? Should I take anything into account in terms of efficiency?

  • Have a look at homebrew.stackexchange.com/questions/1270/shorter-brew-day
    – Philippe
    Commented Oct 2, 2017 at 13:28
  • Thanks, but I only have around 2-3 hours per session, so will never be able to get it all done in one go anyway.
    – Sander
    Commented Oct 2, 2017 at 13:37
  • Do you have a fridge or freezer big enough to store the wort in a carboy?
    – Philippe
    Commented Oct 2, 2017 at 14:33
  • Yes, I have a fridge that I ferment in
    – Sander
    Commented Oct 3, 2017 at 6:11
  • Unless you have an over dimensioned heat source the heating of water/wort takes considerable time.
    – skyking
    Commented Oct 3, 2017 at 14:32

2 Answers 2


Pretty much what you have suggested, I would this.

Day 1 (2h40) :

  • Heat water (30 min)
  • 60 minutes mash (60 min)
  • Batch sparge (30 min)
  • Store carboy in fridge (20 min)
  • Cleaning (20 min)

Day 2 (2h40):

  • Bring water to boil (30 min)
  • Boil with hops addition (80 min)
  • Cool with wort chiller (20 min)
  • Ferment (10 min)
  • Cleaning (20 min)

If the wort is stored in a fridge, I would not boil it the first day. There is little chance of contamination if stored at fridge temperature (about 4°C).

  • 1
    But is it realistic to bring the cooled wort to a boil and get a decent boiltime within 80min? Normally heating water takes considerable amount of time.
    – skyking
    Commented Oct 3, 2017 at 14:17
  • 20 min to get it to boil, depends on many factors. Since OP has only 3h per session, even if it takes 20 min more, it will still be under 3h...
    – Philippe
    Commented Oct 3, 2017 at 14:23
  • Yes, but unless you have an over dimensioned heat source it would take considerable more than that. A source adequate to boil off 10% would take 30min just to bring to boil from sparging. Now you're about to go from 4C to boiling.
    – skyking
    Commented Oct 3, 2017 at 14:29
  • If you take the carboy out of the fridge as soon as you can the 2nd day, it will get closer to room temperature before you start the process. But still you are right, it does take some time to get it to boil. I will edit my answer to add some time for that...
    – Philippe
    Commented Nov 21, 2018 at 13:06
  • Have you actually measured how much time it takes or is it just guesstimates? What heat source do you use to get these times? Bringing water to boil as fast as you heat it for mashing is at least suspicious.
    – skyking
    Commented Nov 22, 2018 at 7:24

I know some people do what they call an "overnight" mash. They will heat their strike water to temperature and move it to their mash tun then dough in as usual. Then, instead of waiting only an hour, they get to it several hours away... sometimes the next morning, hence the name and then sparge as usual. This really shouldn't hurt anything since we want to convert all of the carbohydrates to sugar. Admittedly, this should be done with a cooler type (or at least thermally stable) mash tun so that the heat stays in. I would fill my mash tun with 155 degree water and take a reading 8 hours later to see what happens.

  • As the two days I am able to brew are going to be a week apart I don't think that I will be able to seperate them using this method.
    – Sander
    Commented Oct 2, 2017 at 13:57

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