I've done 2 one-gallon AG brews now, and both have hit approx. 50% efficiency. I thought I'd fixed what was obviously wrong between the two, but the second one still looks like it's going to come out at about 2% ABV... I wondered if anyone could tell me what I am likely to be doing wrong?


I'm aware this is a rather 'rustic' setup! If it's simply a case of needing better equipment then good to know:

  • Heated 1 1/2 quarts of water per lb of grain to 160F in a stock pot
  • Added grain and stirred, temp got down to approx. 150F
  • Put stock pot in a pre-heated (and turned off) oven, and left for 60 mins, checking temp every 15 mins, I was pretty confident I stayed between 148-160 (it got a bit hot at first but I stirred until cooler)
  • Poured mash into large fine mesh colander over bucket
  • Then slowly poured 170f water heated in separate pans over the top, trying to cover as much of the grain as possible
  • This took about 15 mins before hitting 1 1/2 gallons pre-boil volume
  • Cleaned out stock-pot, added colander on top and recirculated wort through grains
  • Then brought to a rolling boil and followed hop schedule
  • Then cooled in 20 mins to 75F in an ice bath
  • Poured through fine mesh strainer into fermenter
  • Was slightly below 1 gallon (probably due to large stock pot, big surface area) so topped up with water, but not much
  • Pitched yeast etc

Was aiming for OG of 1.050 (it's an APA), and I've hit 1.035... which is obviously not great. Where is the most likely misstep? I'm thinking sparging, as the water got through so quickly...

Any tips much appreciated!

  • Can you list the ingredient amounts and types of grain as well. Are you crushing the grain yourself or was it done at purchase time? I'm used to 5 gallon recipes so can't comment on sparge time since you're dealing with less volume.
    – DHough
    Jan 23, 2017 at 18:45

3 Answers 3


That part where you said that "it got a bit hot at first" is likely your culprit. The enzymes that break starches down into sugars (Amylase) don't like getting too hot and they die off. It's far better to start too cool and increase the heat to get where you want it (in fact, many recipes use this method -- it's called step mashing).

  • Thanks, I'll try and be a bit more careful with the temps in that case.
    – user14605
    Jan 23, 2017 at 21:29

My efficiency was low (but not as low as yours) until I made two changes:

  • grain crush: I now run the grains twice through my LHBS grain mill to get a finer crush
  • mash pH: I discovered that my water pH is very high and my mash pH was nowhere near the optimum. Now I measure the mash pH and adjust as necessary to get in the 5.2 - 5.6 range

My mash efficiency is now typically 75-80%.

  • 1
    Thanks for that, i'll give the crush a go. How is mash PH adjusted?
    – user14605
    Jan 24, 2017 at 9:48
  • Usually with acidulated malt or food-grade lactic or phosphoric acid.
    – bughunter
    Jan 24, 2017 at 17:35
  • Acidulated malt, lactic or phosphoric acid are commonly used to lower the pH. If you have a lot of dark grains you may find that the mash pH is too low (it depends on your water), in which case you can add a bit of baking soda to increase it. Jan 25, 2017 at 3:44

What is your sparge run off SG (the very last wort from the sparge)? It should be much lower than your preboil SG. If not, most of your mash product will still remain inside your grain. Only 15 minutes sparging seems way too fast. Increase sparge time preferable to 30 - 40 minutes at minimum. One way of doing that is increasing grain crush.

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