Back to Shopping at

Huge Jump in Efficiency w/ Ovenight Mash

OK, I got lazy and did an overnight mash. I had previously done only a 60-90 minute mashes. Everything was the same on my standard house RIPA recipe as usual. I normally get 70% efficiency on my house RIPA, but from the last three brew weekends I have been up around 93%. I repeated the overnight mash twice more to verify my results and had the same 93% extract efficiency.

I have well over 100 all-grain brews under my belt and I can do my house recipe in my sleep. I did not change my mill gap, grain or anything else. The only difference was I started the mash the night before I sparged. Everyone always told me 60 minutes was sufficient, but this seems to indicate poor enzyme activity from my base malt? I use Canada Malt 2-row pale (75% by wt), Weyermann Malted Rye (20% by wt) and Dingmann’s Special-B (5% by wt). All my grain is fresh and milled hours prior to mashing. Several years ago I would typically get 85% efficiency, on a one hour mash when using Franco-Belges 2-row pale malt, but have not been able to get it at a reasonable price after the Country Malt Group halted selling to clubs.

Has anyone else had this experience?

First, efficiency is at least somewhat dependent on the malt you have and how close to the average ppppg it is. So thats one variable.

Second, with a coarse crush I do think you can leave some starch behind with a 60min mash, and overnight the amylases will continue to work on these pieces from the outside in. You might try reducing your gap a bit to get a finer grist, that can lower the time it takes to convert those larger chunks.

I usually do a 90min mash if I’m not in a hurry, or if I’m doing a no-sparge where I mash with my full volume of water (3.5qt/lb).

I use a fairly fine gap of 0.040" on my Monster Mill and close to flour consistency.

I’ve brewed the Speckled Heifer (Spotted Cow clone) 3-4 times in my brewing life history. The last two times, I’ve performed overnight mashes. For the third time (first overnight mash), I reached 90+% brewhouse efficiency, which seems too good to be true. For the fourth time (second overnight mash), my efficiencies—however you’d like to measure them—weren’t significantly different than the other times I’ve brewed the beer (i.e., without overnight mashes).

Could be the crush. I now crush at 0.028" or thereabouts. I think that’s down from 0.040" or thereabouts from the first couple brews of this beer.


I’ve seen a significant drop in my BHE the past year. I used to be 90+ and now am pretty consistent at 70-75%. Greymane, you’re making me want to give overnight mashing a try and see what it can do for me.

Same here, except it has been a few years since mine dropped suddenly from 90+% to 70%. I’m thinking the enzyme levels in the malt aren’t what they used to be several years ago.

I use a fairly fine gap of 0.040" on my Monster Mill and close to flour consistency.[/quote]
I would consider that a fairly standard gap, perhaps slightly coarse, not fine. I use the Canada Pale Ale Malt and get 85%+ efficiency in an hour, so I don’t think enzymes are your problem. However, I use a smaller gap. I don’t know what it is, but it is tightened down from the 0.39 that my mill came with, which didn’t result in complete conversion, for me. Perhaps the Belgian Pale was a plumper malt, so crushed better at that gap.

If 70% is your standard efficiency, then it does sound like you have not been achieving complete conversion, unless you don’t sparge or have a lot of dead volume.

Crushing finer would probably increase the rate of conversion. Another thing that can help is a step from your primary mash temperature up into an Alpha Amylase rest in the 158-162F range for 10+ minutes. This can improve galatinization, helping coarser grits to convert. This is usually required on my system to get near complete conversion. I just do this step instead of mashing out.

Back to Shopping at