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Still getting a way low OG and I'm about to snap

Ok, posted on my last brew day that I’m coming in low in my OG. Brewed today and it’s worse than ever. Here we go…

13.5 Marris Otter
.5 carapils
.25 C60
.25 C120

Mashed in at 2qt per lb whick was roughly 7.5gal at 153 degrees. I assumed .2qt per lb for absorption. I mashed in with 2.5gal sparge water. I batch sparge in Denny’s cooler. Wound up with about 6.5 in the kettle. Had about 2qt remaining in the mast tun. I should have had an OG of 1.077. It was 1.061. Was shooting for a strong English ale and damn near ended up with a session. What is going on?

You say you had 6.5 gallons in the kettle. What was left after the boil. What was your BG

6.5 pre boil. I use a keggle and I regularly boil off 1.5gal. I wound up with almost 5gal exactly post boil.

Whose crushing your grains? If you, have you checked your gap lately?

Mind the gap

We all need to converge at Taco’s house to brew. We’ll nail the problem to the wall!! Sneezles61

On Tuesday

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Someone say tacos? I’m in!

I agree that crush is the first place to look but I’d also check your efficiency. Is this your own recipe or a kit? What efficiency was it created for and what efficiency do you normally get?

Then crush harder.


Was that your pre-boil OG or your OG in fermentor? What is your typical efficiency? Plugging your numbers into Brewer’s Friend Calculator 1.077 pre-boil would be 92% efficiency. I use Denny’s cooler setup and typically get mid to upper 70’s for efficiency. 1.061 is just shy of 73% which for my setup is right in the range for a similar grain bill. I typically mash between 1.4 qt/lb and 1.7 depending on grain bill. For bigger grain bills I oversparge and boil down to starting volume. If you crush your own grains and have seen that big of a drop, you may want to check your mill gap as others have said. If your LHBS is crushing for you, maybe ask for a double crush. These numbers change significantly if that was your OG reading in the fermentor for 5 gallons.


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If all else fails, base malt is pretty cheap. Just add more until you reach your target.


It is my recipe. My pre boil grav was 1.050 and ny OG into the fermenter was 1.061. I get my grains crushed at my LHBS. Jay runs a good shop so I would imagine the mill is calibrated but I will start doing a double crush. And yes sneezles, I need everyone to travel to Northern California for a brew day to iron this baby out! I could just add some base, bit I would rather figure out my problem so I’m not just doing it by the seat of my pants. Can you expand on how you over sparge and boil down?

Rad, I got 1.077 from putting the recipe in brewers friend. I put the grain bill in brewers friend to check efficiency and it said I got 59. I don’t understand because I use spring water, I hit my temp on the head. Every aspect of my mash went off without a hitch.

For my system, I have my calculator set for .12 Gals/lb absorption, .25 gal volume loss to dead space, 1 gal/hour boiloff, and trub loss of .25 gallons. What I mean by oversparging is for example, I brewed up Denny’s BVIP last weekend which has a 17.75 lb grain bill. I mashed with a ratio of 1.4 qt/lb which should be 6.25 gal on my system. This means I should sparge with roughly 2.8 gallons to hit my target preboil volume of 6.63 gal for a 70 min boil. I sparged with 3.25 gallons and mashed with a bit more than 6.25 so my total volume in kettle after sparging was over 7 gallons. I then boiled down to 6.63 before I started my timer. I have found that doing this helps especially with bigger beers for me.

One time I had an issue with my mill and got 65% pre-boil efficiency so I knew something was not right. I broke it down and got it all set up properly again and clean and was right back to my standard of mid 70’s. I’ve been AG brewing for 2 years now so I know my system pretty well. What is your typical efficiency on your system? Is it always in this range or has it dropped on more recent beers? If nothing else has changed on your system and you’re hitting your numbers on the head like you say you are, then the only real variable is crush.


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To be honest, I only recently started checking my efficiency because I bought a refractometer. I’ve always wound up a bit low on my abv but never really questioned it, just assumed I needed to improve on my techniques. But I feel Im doing everything correctly and still ending up way low on my OG. It’s frustrating.

I agree with Rad’s points above. The only thing that jumped out at me is your use of spring water? You mean bottled spring water? If you’re going to buy water you should by distilled so you know what you’re starting with and can build it up for the correct water profile for the beer your brewing. With spring water unless you can get analysis from the company and belienve it’s consistent you’ll never know what pH you’re mashing at.

I don’t believe pH has a whole lot to do with your low efficiency but it’s another variable you may want to get a handle on at some point to have more consistent results.

Your LHBS may be a great, reputable shop but they’re going to set the mill on a setting that allows them to crank out the grain quickly and make the mill easy to clean. It just may not be crushed as finely as you need it. Ask him what he setting he uses for the mill.

If you rely on someone else to crush your grain you pretty much have to deal with what you get. So that could mean if you create a recipe based on 75% efficiency but you’re getting say 65% efficiency you’ll just have to create your recipes based on 65% and add more grain.


I’ll toss in another suggestion. Refractometers may give false readings. I gave up on mine about a year ago.

I was intermittently getting lower than expected SG readings. In frustration I did a quick test using table sugar solutions in water. I measured each sample with both the ‘calibrated’ refractometer and the hydrometer. The two devices were consistent to about up to about 1.050. When SG exceeded 1.050 the refractometer reading dropped of quickly. Above 1.050 the refracto dropped off to 6% lower than the hydrometer at 1.080. I assumed that the old school low tech hydrometer is the more accurate device so I quit using it. (ATC refractometer was calibrated to 1.000 with distilled H20)

I just tested another batch yesterday, same deal. Got 1.073 by refractometer and 1.077 by hydrometer.

I researched this discrepancy and didn’t find much definitive information. One article I found suggested that refractometers need an additional calibration (I interpreted this to mean correction table) for homebrewing. Something to do with the type of sugars in solution and each refract light differently.

This is probably device dependent. Mine is a low end unit.

If you have a hydrometer, it is a quick test to make up a simple sugar and water solution (10 parts water to 1 part table sugar by weight) and test with both devices. Dilute the solution and repeat the test until you get to about 1.030.

good luck

Calibration is needed a few times a year for refractometers and thermometers. Another thought that crossed my mind is actual weight of yer grist. Do you also weigh it when home? You may have stated that and I missed it, but take a look and verify. I’m not stating yer LHBS is taking you, maybe his scale is off and needs attention. Yer apparent efficiency is 63, I would be trying to find a way to increase that too! Sneezles61

Wow, that’s interesting.

I started using a refractometer years ago and did a single-point comparison early in the game, but that obviously wouldn’t show what you describe here. Aside from some occasional concerns about the consistency of readings done at high temps, I’ve never suspected it was low, but who knows.

I think I got the refractometer around the time I went all-grain and according to those measurements my efficiency has always been in the high 60s to low 70s, which I don’t care much about as long as it’s consistent, but would be interesting to confirm it with an experiment like yours.

Have you kept notes on mash pH for different beers? pH may need to be adjusted for Beta-Amylase and Alpha-Amylase enzymes to work together. Experimenting with a thicker mash may also be worthwhile to compare the effect on efficiency.

Some thoughts on the OP:

-The sum of your mash and sparge volumes is 10G, and you say you got 6.5G into the kettle. If I have that right, it means your absorbtion/deadspace/leftover is 3.5G, which is a quite a lot even for the substantial amount of grain in your bill. That 3.5G sitting in your MLT has the same OG as your 2nd runnings, which in your case is probably pretty high because your sparge volume was quite low. That in itself is going to limit your efficiency substantially.

-Along those lines, you mentioned that you had 2qt remaining in the mash tun…I assume this is because you couldn’t fit it all in the kettle? If I interpret what you’re saying correctly, this is sugar you’re throwing away and it directly affects your efficiency. You should certainly avoid doing that if you can.

-If you’re not considering your water and mash pH, you probably should.

-You should be able to look at your crushed malt and conclude whether it’s a possible issue. I bought my own mill, which I never thought I’d do, because even the LHBS that I love wasn’t giving me consistently crushed grain. The grain looked “ok” for the most part after crushing at the shop, but now that I crush my own, the difference is painfully obvious. We can share photos here if you’re not sure what it should/shouldn’t look like.

I think you can definitely track down the source(s) of your problem if you want to, but it’s going to require some work. Great beer does not depend on brewhouse efficiency, so as others have said it may not be that big a deal. With that said your numbers indicate that you’re getting <60% brewhouse efficiency, and you really should be able to beat that if you’d like.

Hope this helps!

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