Author Topic: Poor mash extraction / low pre-boil gravity  (Read 655 times)

Offline kennedmh

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Poor mash extraction / low pre-boil gravity
« on: April 17, 2019, 05:31:24 PM »
So, I'm not sure where to begin other than saying that I need help with my mash gravities and I don't know where to start looking. 

I'm an all-grain brewer and have been for a decade but I laid off for about five years when my twins were small.  Now that I'm getting back into it, I have a recurring problem with getting good extraction from my mashes.  I regularly will miss my OG low and have to add DME to the boil to bring my gravity in line.  Obviously less than ideal.

I monitor my temps pretty closely.  I use a 10 gallon Gott cooler as my mash tun.  It loses about 5 degrees over the course of an hour long mash, but that's OK, I start on the high side of about 155 and let it drag down across to about 150 when the mash is done.

I always do a iodine check at the end of the scarification rest to ensure conversion and that always passes.

I don't check pH but I build my brew water using the Bru'n Water spreadsheet.

I batch sparge (could that be it?  Just too inefficient of a sparge to rinse all those sugars out?).

Example: I made a pilsner last weekend with the following ingredients (and a slightly modified mash schedule to include a decoction mash to reach mashout and a higher water/grain ratio of 2qt/pound)

--11.5# Pilsner malt
--1.0# crystal malts (cara-pils and melanoiden)
--0.25# acid malt for mash ph

--20min rest at 133
--60 min at 154 (drifted to 150)

--Single batch sparge with 5gal of water.

Anyhow, I'm looking for advice on problems to look for to figure out why my mash efficiency is low regularly.

Thanks!
« Last Edit: April 17, 2019, 06:58:02 PM by kennedmh »

Offline dls5492

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Re: Poor mash extraction / low pre-boil gravity
« Reply #1 on: April 17, 2019, 06:41:00 PM »
When you stated "2qt/gallon", I am assuming you meant 2qt/pound of grain, right? Do you mill your grains or did someone else do that?
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Offline kennedmh

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Re: Poor mash extraction / low pre-boil gravity
« Reply #2 on: April 17, 2019, 07:00:56 PM »
When you stated "2qt/gallon", I am assuming you meant 2qt/pound of grain, right? Do you mill your grains or did someone else do that?

Ha, yes, thanks for catching that.  I updated the original post. 

And my local brew supply shop mills the grains for me when I buy them.  Looks like a reasonable grind to me.  I don't see any whole barley kernels in there when they are done.

Offline dls5492

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Re: Poor mash extraction / low pre-boil gravity
« Reply #3 on: April 17, 2019, 07:04:39 PM »
How do you measure your OG? Did you check your measuring devices?
David S.
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Offline RC

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Re: Poor mash extraction / low pre-boil gravity
« Reply #4 on: April 17, 2019, 07:07:04 PM »
It may not be a problem, it may just be physics. Batch sparging generally results in lower efficiency than continuous sparging. With me, my batch sparge efficiency is around 70% while my continuous sparge is around 90-95%. Big difference, obviously. Other brewers no doubt experience a different range of efficiencies, but the pattern is likely the same: batch sparging comes with reduced lauter efficiency.

You might be able to eek out a few more gravity points with a finer crush and stirring the mash occasionally. But the main solution is simply to build your recipes around the lower efficiency, which means you'll use more grain is all.

Offline kennedmh

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Re: Poor mash extraction / low pre-boil gravity
« Reply #5 on: April 17, 2019, 07:08:25 PM »
How do you measure your OG? Did you check your measuring devices?

I use a hydrometer that's calibrated for 60 degrees that I've checked with tap water.  I use Beersmith for telling me the temp adjustment based on the temperature of the sample.

Offline kramerog

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Re: Poor mash extraction / low pre-boil gravity
« Reply #6 on: April 17, 2019, 07:12:24 PM »
Milling is the first suspect.  Looks like we can cross that off.

Please provide volumes of wort and gravity.  Target gravity vs. actual gravity.

EDIT: deleted discussion of mash and sparge volumes because my mental arithmetic was off.

On as separate note, I think you would be better off doing a decoction mash around 149 and 160F rather than 133 and 154, but I'm not an expert on this.

EDIT: I ran some quick calcs - I'd expect a preboil gravity of approx 1.039 and a brewhouse efficiency of approx 86% for this batch.

Online BrewBama

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Poor mash extraction / low pre-boil gravity
« Reply #7 on: April 17, 2019, 07:29:27 PM »
Have you seen this: http://seanterrill.com/2013/10/05/batch-sparging-calculator/  I like to poke my numbers into it as a brewday sanity Ck.

What is your definition of “low mash extraction”? How do you determine your target?  I routinely get 90% +/- 2% mash efficiency  (calculated by BeerSmith) batch sparging so disagree with the “you get less efficiency than continuous sparging” camp. 

5 gal batch?  I poked your grains into BeerSmith and get 1.061 for my system using my processes. What did you get?

Why the 133*F 20 min rest?  Ever considered mashing in at 152*F-154*F instead?





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« Last Edit: April 18, 2019, 11:43:45 AM by BrewBama »
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Offline denny

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Re: Poor mash extraction / low pre-boil gravity
« Reply #8 on: April 17, 2019, 08:05:13 PM »
It may not be a problem, it may just be physics. Batch sparging generally results in lower efficiency than continuous sparging. With me, my batch sparge efficiency is around 70% while my continuous sparge is around 90-95%. Big difference, obviously. Other brewers no doubt experience a different range of efficiencies, but the pattern is likely the same: batch sparging comes with reduced lauter efficiency.

You might be able to eek out a few more gravity points with a finer crush and stirring the mash occasionally. But the main solution is simply to build your recipes around the lower efficiency, which means you'll use more grain is all.

My batch sparge efficiency is 83-85%.

OP, do you know what you average efficiency is and did you adjust the recipe for it?
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Offline chinaski

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Re: Poor mash extraction / low pre-boil gravity
« Reply #9 on: April 17, 2019, 09:27:24 PM »
Is your efficiency consistent?  If so, I wouldn't sweat it- adjust your recipes and move on.  Consistency will allow you know exactly what you'll get out of each brew session- that's worth a lot more than a few efficiency points in my book.

Offline Visor

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Re: Poor mash extraction / low pre-boil gravity
« Reply #10 on: April 18, 2019, 05:00:34 PM »
   I'm with BrewBama on the issue of bath sparging efficiency, depending on the recipe I my M.E. is usually in the upper 80's or low to mid 90's, only rarely is it in the low 70's.
   The fact that your LHBS mills your grain doesn't necessarily remove that as a possible contributor to your low efficiency.
   Other may poo-poo the idea of preheating your mash-tun cooler, but I do so with my boiling sparge water and usually only see a temp drop of 1 or 2 degrees, again depending on recipe. While a 5* temp drop during mash won't ruin your beer, I prefer to stay as close to my target temp as is reasonably possible, and preheating only costs me a couple of minutes.
   I would think that 5 gallons of sparge water is plenty, when possible I generally sparge with about 35% - 40% of the total water volume, and sparge runoff volume is usually about the same as mash lauter volume.
   Yes you an adjust your recipes to account for low efficiency, I for one hate waste and always try to maximize efficiency, were it me I'd keep looking until found the source or sources of the problem.
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Offline Robert

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Re: Poor mash extraction / low pre-boil gravity
« Reply #11 on: April 18, 2019, 05:58:13 PM »


   
   The fact that your LHBS mills your grain doesn't necessarily remove that as a possible contributor to your low efficiency.
   

Quite the opposite.   The fact that your LHBS mills your grain makes this far and away the most likely cause.   Shops are notorious for setting their roller gaps extremely wide (factory settings on homebrew mills are similarly wide.)   Maybe they don't want to have newbies put off by a possible set mash, maybe they just want you to get a low yield so they'll sell more grain... whatever.  See if you can find out where they have it set.  Ask if they can adjust it.  If not, ask them to double crush your grain.  See if this helps.  And if you're really concerned about this and don't want to just adjust your recipes to account for the yield you're getting, consider buying a mill.  Meanwhile, you may be doing nothing wrong, as others have said.  RDWHAHB.
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Offline kennedmh

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Re: Poor mash extraction / low pre-boil gravity
« Reply #12 on: April 19, 2019, 10:56:41 PM »
Been away for a few days, but I'm back and lets see if I can answer the posed questions.

So, a couple times I was asked what my efficiency is (I don't know) and if it's consistent (it is not).  I have not calculated my current mash efficiency, but it sounds like I should be doing so.  I haven't because, well, Beersmith tells me what my gravities should be at certain steps in the process, and I just follow that.  I don't know if calculating my efficiency will be of much value because, well, it's so inconsistent.  The pilsner recipe I included in the OP was came in at 1.036 pre-boil when Beersmith said I should be at 1.042.  However, the previous beer I made, a British style Premium Bitter, was bang on my pre-boil gravity.  Why was it different?  I have no idea.  Sometimes I hit my target gravities, sometimes I don't.  I don't know why sometimes and not others.

In terms of adjusting my recipes for lower extraction, I generally plan about an 10% in grain to try and make my target gravities.

Ultimately it sounds like the consensus here is that I don't have enough information to know why I miss badly sometimes and not others when I think I'm doing the same thing each time (though different recipes have different mash schedules so maybe it's something in there?).

Are there common pain points that I should be on the lookout for?  Is it generally OK to trust in Bru'n water for mash pH or am I a fool not to use a pH meter to check my mash?  I generally feel like there's not much I can do about it once the mash is in process but maybe I should get some lactic acid for times it's too high?

Both my kegs are empty (last one ran dry last night) so I need to brew again next weekend.  I'll try and religiously and see if I have better luck and will be able to provide more information to hopefully ask you folks again to get to the bottom of this.

Offline KellerBrauer

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Re: Poor mash extraction / low pre-boil gravity
« Reply #13 on: April 20, 2019, 11:58:01 AM »
My thought is the Equipment Profile you’re using in BeerSmith is off.  I struggled for about a year to get my Equipment Profile, BrewHouse efficiency and Mash Efficiency accurate in BeerSmith.

Go into BeerSmith and record the BrewHouse efficiency you got from a brew you recently completed.  Now, go into the base Equipment Profile you use when creating a recipe and change the BrewHouse efficiency to the one you just recorded.  Now recreate a new recipe identical to the recipe you’re inquiring about using the newly created Equipment Profile. I will be willing to bet you will need more grain to achieve the same OG results.
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Offline dmtaylor

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Re: Poor mash extraction / low pre-boil gravity
« Reply #14 on: April 20, 2019, 12:18:05 PM »
And my local brew supply shop mills the grains for me when I buy them.  Looks like a reasonable grind to me.  I don't see any whole barley kernels in there when they are done.

There is your problem.  Get your own mill.
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