How do you deal with undershot gravities?

[morbster]

I was brewing a Hefeweizen yesterday and noticed my pre-boil gravity was way low (1.029 actual vs. 1.040 target, volume was pretty spot on). I wasn’t completely surprised by this, because I was lazy and let my LHBS crush my grain instead of doing it myself. I bumped up my boil vigor to hopefully drive up the gravity a bit, and I ended up with an OG of 1.040 vs 1.050 target. I plan to call it a lite hefe and just not worry about it.

It made me wonder though: what do you guys do when you notice your gravity is off by that much? I suppose I could have boiled some DME and bumped up the gravity, but I don’t know if that has any impact on flavor or other areas.

 

[RPh_Guy]

I never adjust it. It's still beer and still alcoholic.

 

[IslandLizard]

Most likely the crappy wide gap at your LHBS didn't crush your wheat very well (small kernels). You may have lost some wheat character due to that.

When I see my first runnings being a bit low on gravity, I sparge less (batch sparging). And/or boil 3rd running on the side (on the stove) to condense them more. I'll end up with a somewhat smaller batch, but it's closer to the gravity I want.

If it's only a few points off, I rarely worry about it. Or as you did boil a little longer, but before adding hops and start the brew clock.

You could brew a small, super concentrated batch, say a gallon if you have enough headspace in your fermenter.

Or just add some dissolved and pasteurized (wheat) DME. Hold at 160-170F for 10-15'.

 

[morbster]

Most likely the crappy wide gap at your LHBS didn't crush your wheat very well (small kernels). You may have lost some wheat character due to that.

Good thought, @IslandLizard. I knew I would regret being lazy and having them crush for me. I’ll most likely follow the path of @RPh_Guy and not change anything. I don’t want to disturb my cute little yeasties who are chomping away right now.

I don’t mind the lower ABV (looks like I’ll be lucky to hit 4%), but I hope the flavor and body is still adequate.

 

[FatDragon]

These days, I mostly do double batches in my 9 gallon kettle by brewing a high-gravity wort and splitting it into two fermenters with top-off water. If I was worried about the gravity being too low, I'd reduce my top-off water and thus batch size. In a more typical brewday, I'd boil longer. The one time I tried to do a hefeweizen, I had the same problem, only it was my own corona mill that was poorly adjusted and let most of the wheat slip through. It was insipid. I don't recall if I ended up dumping most of the batch or cooking with it, but I didn't drink much of it.

Extract is another good option if you have some. Here in China, it's stupid expensive so I never really have it on hand and can't just pop over to an LHBS to pick some up like I could probably do if I were back in the States.

 

[SEndorf]

I never adjust it. It's still beer and still alcoholic.

This...…
My first question is always "who, or what" told you it should be 1.040 ?
Beersmith ? A kit ?

 

[passedpawn]

I usually hit my gravity. I just boil til I hit it. This is one of the best uses of a refractometer.

There have been a few times when my mill was whacked and I had terrible efficiency. Those times, I went to the homebrewshop and just added DME to the fermentor to bring it up. Word to the wise: add slowly, a little at a time over an hour. If you add it all at the same time, it will erupt.

 

[FatDragon]

I usually hit my gravity. I just boil til I hit it. This is one of the best uses of a refractometer.

There have been a few times when my mill was whacked and I had terrible efficiency. Those times, I went to the homebrewshop and just added DME to the fermentor to bring it up. Word to the wise: add slowly, a little at a time over an hour. If you add it all at the same time, it will erupt.

Why not just dissolve it in a cup of boiling water? You get a little pasteurization and avoid the volcano, and at one cup in a 5+ gallon batch - even if you add it to the fermenter at boiling temps - the absolute worst harm it might do is to boil the yeast in a couple cubic inches of krausen before it stabilizes at fermentation temp.

 

[Still Brewn]

Or still add some dissolved and pasteurized (wheat) DME. Hold at 160-170F for 10-15'.

I would do this or just add an equivalent amount of sugar to make up the difference for a non wheat beer. The math is easy enough to get your og.... most of the time I don't worry about it.

 

[passedpawn]

Why not just dissolve it in a cup of boiling water? You get a little pasteurization and avoid the volcano, and at one cup in a 5+ gallon batch - even if you add it to the fermenter at boiling temps - the absolute worst harm it might do is to boil the yeast in a couple cubic inches of krausen before it stabilizes at fermentation temp.

Yea, that would be better, and easier. If I have to do it again, that's what I'll do.

 

[eric19312]

Like @passedpawn I use a refractometer to get gravities during the process and almost always got me pre boil gravity. With pre boil gravity known and pretty good idea of boil off rate it is never really an issue to hit target within 1-2 degrees SG by reestimating your boil time at the start of the boil. Then if you are going to increase the time you just hold your first hop addition until there is 60 minutes left to go ... assuming your plan had been for a 60 minute boil with hop addition at start of boil. This method adds time to the brew day, might lead to darkening of your wort, and reduces overall yield.

There is an easier way. In If I am brewing an IPA or any belgian style I have no issue with adding up to 10% table sugar into the boil either at beginning of boil or into the whirlpool. Table sugar is 46 points per gallon. In a typical grist aiming for 1.050 beer that could add 7-8 SG points. For belgians that already had some sugar in the recipe I'd be willing to go to total sugar in the recipe of 20% and maybe higher with a little more internet research. In that case I'd probably hold some of the sugar to add late in fermentation.

For styles where sugar would not be appropriate I usually have some DME on hand for starters. That can go in at the end of boil.

 

[kh54s10]

I too, usually just let 'er ride... But one batch was really low and I caught it early so I added DME at the end of the boil. I was still a little low.

 

[Jayjay1976]

I brewed a 1.054 Hefe yesterday.. and as always I nailed my pre- and post-boil numbers thanks to my trusty Cereal Killer. I tightened it down to the smallest gap on the day it arrived and haven't touched it since (I BIAB). Only time I worry about hitting my numbers is with beers over 1.085 due to the reduced efficiency of a thicker mash.

 

[FatDragon]

I brewed a 1.054 Hefe yesterday.. and as always I nailed my pre- and post-boil numbers thanks to my trusty Cereal Killer. I tightened it down to the smallest gap on the day it arrived and haven't touched it since (I BIAB). Only time I worry about hitting my numbers is with beers over 1.085 due to the reduced efficiency of a thicker mash.

Have you tried doing an iterated mash on big beers? I've done quite a few big BIAB mashes between big beers and split batches, and almost all of them have been a huge pain. Last brewday, I decided to mash half of my grain, pull, mini-sparge, and squeeze the bag, and then use the wort as strike water for mashing the second half of the grain. I did the first step after my wife and kids went to bed, mashed for an hour or so, then did the second step as an overnight mash. Got up in the morning, boiled, chilled, topped off, pitched, and washed my pots and buckets. It was so much easier than trying to fight with an over-stuffed bag and draining and squeezing for an hour or two before finally giving up on the last half gallon of wort trapped in the grain, and efficiency didn't suffer. I'd suggest it to anyone struggling with a big BIAB grain bill.

 

[morbster]

Last brewday, I decided to mash half of my grain, pull, mini-sparge, and squeeze the bag, and then use the wort as strike water for mashing the second half of the grain. I did the first step after my wife and kids went to bed, mashed for an hour or so, then did the second step as an overnight mash.

Interesting idea; I've never considered splitting a mash up like that. What were your mash time/temp for each one?

 

[Jayjay1976]

Have you tried doing an iterated mash on big beers? I've done quite a few big BIAB mashes between big beers and split batches, and almost all of them have been a huge pain. Last brewday, I decided to mash half of my grain, pull, mini-sparge, and squeeze the bag, and then use the wort as strike water for mashing the second half of the grain. I did the first step after my wife and kids went to bed, mashed for an hour or so, then did the second step as an overnight mash. Got up in the morning, boiled, chilled, topped off, pitched, and washed my pots and buckets. It was so much easier than trying to fight with an over-stuffed bag and draining and squeezing for an hour or two before finally giving up on the last half gallon of wort trapped in the grain, and efficiency didn't suffer. I'd suggest it to anyone struggling with a big BIAB grain bill.

I really like this idea, thanks!

 

[FatDragon]

Interesting idea; I've never considered splitting a mash up like that. What were your mash time/temp for each one?

I targeted the same temp each time, right around 66.7C. The first mash was an hour or maybe a bit more. The second was overnight because that fit my schedule best, but I believe I could have stopped it at an hour like any other mash. Other methods I've tried to do big BIAB mashes have always been more work and worry, so I think iterated mashing for big beers and split batches will be my new go-to practice.

 

[CascadesBrewer]

I don't think I have ever adjusted a beer up with extract/sugar or down with water...though I suspect there were a few that I should have.

For many years, the first time I took a gravity reading was after my wort was chilled and being transferred to the fermenter. At that point it was a bit too late to easily adjust. While I did not measure every step of my process, I knew enough that if I plugged in 75% efficiency and my grain bill into the application I was using that I would get close enough. My volume was usually spot on, just because I fly sparged until I got my target pre-boil volume. I would really have to screw up something to get an OG more than 10% off, even with a new recipe.

These days I am more in tune with each step of the process and I picked up a refractometer a few months ago to help with brew day gravity readings. I moved to BIAB a few months ago, and I have been playing with my process and also doing several 2.5 gal stovetop BIAB. I still find that I am getting close enough OG to what I want, that I have not felt the need to adjust...and I will feed my lessons into the next batch.

The time I have put into understanding my process has helped out. Yesterday I brewed an IPA targeting 5.5 gals into the fermenter at 1.065, I got 5.4 gal into the fermenter at 1.065.

My first question is always "who, or what" told you it should be 1.040 ?

Agree. OG is just a yardstick measurement. I am usually targeting a general ABV range for a beer. If I target 6%, does it really matter if I end up with a 5.5% beer or a 6.5% beer? Even if that swung out to 5% or 7%, the beer might a touch out of balance or maybe a little off from what I was shooting for. I would not be surprised if people could not tell the difference between the 5% and the 6% version of the beer in a blind taste test.

I was lazy and let my LHBS crush my grain instead of doing it myself

That was really the motivation for me to buy a mill. My local shop sold bags of pre-crushed, but would only mill small amounts of specialty grain (they have a public mill now). Between those bags, and bags of pre-crushed grain from online vendors I was seeing big efficiency swings. My grain mill really smoothed that out for me.

 

[tsholl]

Do you add water (e.g., make a 5 gallon batch but only boil 3 gallons?). If so here's what I do. I boil the three gallons, and then first just add one gallon. Then I take an OG reading. Let's call that OG reading X. Let's call the volume thus far Y. Y is usually around 4 but may be slightly less if some boiled off. Then I calculate how much water I want to add to achieve a desired OG. Let's call the amount of water to add Z. As you know water has an OG of 1.0. Finally let's call your desired OG W...

(X*Y)+(1*Z) = W*(Y+Z)

Then just solve for Z. I usually do this by playing around in Excel...

So say your volume after adding the one gallon is 4 gallons, and your OG is 1.045, and you want an OG of 1.04. Then...

(1.045*4)+(1*Z) = 1.04*(Z+4)
4.18 + Z = 1.04Z + 4.16
4.18 = 0.04Z + 4.16
0.02 = 0.04Z
Z = 0.5

So in this case I would only add half a gallon of water to bring the OG to 1.04. Adding the full gallon would dilute it too much.

 

[RPh_Guy]

(X*Y)+(1*Z) = W*(Y+Z)

Then just solve for Z.

Z = Y * (X - W) / (W - 1)

 

[seatazzz]

Thanks for bringing back the nightmares of high school algebra.

I always shoot for a 90 minute boil, and check the gravity when it hits 60; if the gravity isn't where I want it, I can either let it go a bit longer before adding the hops, or if the volume looks iffy will ramp down on the gas for a lighter boil/less boiloff. For basic ales I'm usually at 1.040 preboil, and wind up in the low 60's when all is said and done. Might get a short keg once in a while, but would rather have that than sub-par/gravity/flavor beer.

 

[balrog]

Thanks for bringing back the nightmares of high school algebra.

BrewersFriend Dilution/Boiloff Calculator FTW

 

[balrog]

To the OP's original question of what to do when low preboil SG:
It's only happened once really. I blame buying pre-double-milled from Ritebrew for years for being too damned consistent. But when I got my Corona and started milling (to dust basically) and did my tried and true Blue Moon wheat beer recipe the first time on the new mill it caught me off guard by nearly 10pts low. I just kept going and it was what it was. Next time, I adjusted, since I keep prolific notes on everything.

If I could just find them when I want them...

 

[Jordan Logo]

This literally just happened to me... I switched from Extract to a 1 gallon BIAB method and got my grains crushed at my LHBS. When I asked about double milling they said I didn’t need to....

My target OG was 1.045 according to BeerSmith but I missed it by .015 points (1.030). I ended up getting some Light DME and using BeerSmith’s gravity adjustment calculator to get it closer.

Next time I’ll run the grains twice through the mill!

 

[HTH1975]

I just add some DME if I’m under gravity, but I normally have the opposite issue (over gravity). I deliberately scale my recipe efficiency so that I have a little bit wiggle room on the higher side as it’s easier to liquor back, or accept a slightly higher OG.

I didn’t have any DME when I brewed yesterday, so I just boiled for longer to get my OG, before adding the late hop additions. In real terms, the bitterness of the first hops doesn’t increase much beyond 60 minutes, so boiling longer doesn’t pose a problem. I actually got an amazing cold break, better than usual, with the longer 120 min boil.

 

[madscientist451]

I usually keep some DME or LME on hand in case I miss my numbers.
Maybe I've been lucky, but I've been hitting my desired pre-boil numbers every time since switching back to BIAB + dunk sparge.

 

[Soulshine2]

I was brewing a Hefeweizen yesterday and noticed my pre-boil gravity was way low (1.029 actual vs. 1.040 target, volume was pretty spot on). I wasn’t completely surprised by this, because I was lazy and let my LHBS crush my grain instead of doing it myself. I bumped up my boil vigor to hopefully drive up the gravity a bit, and I ended up with an OG of 1.040 vs 1.050 target. I plan to call it a lite hefe and just not worry about it.

It made me wonder though: what do you guys do when you notice your gravity is off by that much? I suppose I could have boiled some DME and bumped up the gravity, but I don’t know if that has any impact on flavor or other areas.

Ive never had my gravities come in that low. I usually hit within 0.002
I'd suggest milling the grains yourself .

 

[shortyz]

chuck in another pound of grain, if she ends up a little high on alc who cares.

 

[morbster]

chuck in another pound of grain, if she ends up a little high on alc who cares.

Sounds like a good way to sour a beer since we’re talking about OG, unless you’re saying you would redo the mash.

 

[HTH1975]

Sounds like a good way to sour a beer since we’re talking about OG, unless you’re saying you would redo the mash.

I’d imagine he means that you should just throw more grain in the mash tun to begin with to avoid undershooting OG.

 

[shortyz]

either or, let er rip