Author Topic: Getting low OG.....?!  (Read 989 times)

Offline brewfreeordie603

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Getting low OG.....?!
« on: May 16, 2016, 05:13:08 PM »
I have only been doing all grain brewing for a few batches.  I am using a kettle and 10 gal converted water cooler for the mash tun and doing a batch sparge in the same cooler.  The OG was supposed to be 1.061 for the recipe I was using (an IPA) but I ended up with a 1.042. 

Since many of you are more seasoned at this than me, what things can go wrong during the brew day that could result in lower original gravity?  I can provide any other info that you might need, as the session was well documented.  Thanks in advance!

Offline blair.streit

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Re: Getting low OG.....?!
« Reply #1 on: May 16, 2016, 05:17:32 PM »
You'll get a lot of responses with what could go wrong. Before we get too far down the rabbit hole, can you post your grain bill and describe your mash/sparge process (including how much water you used in each and how much ended up in the kettle pre boil)?

Offline HoosierBrew

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Re: Getting low OG.....?!
« Reply #2 on: May 16, 2016, 05:25:36 PM »
1/ Too coarse a crush on the grains. Probably number 1 culprit.

2/ Volumes off - mash, sparge, preboil. Be sure to measure mash and sparge water accurately, account for grain absorption and dead space, and get an accurate boil off rate/hour on your kettle. This will help you hit your final volume into the fermenter accurately. If volumes are high or low, it affects your concentration of sugars and therefore your OG measurements.

3/ Temp accuracy - you need a thermometer that's accurate enough to hit your mash temp fairly accurately. If you unknowingly are mashing too high or too low, you could be outside the optimal enzymatic range for good conversion.

Jon H.

Offline brewfreeordie603

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Re: Getting low OG.....?!
« Reply #3 on: May 16, 2016, 05:31:27 PM »
You'll get a lot of responses with what could go wrong. Before we get too far down the rabbit hole, can you post your grain bill and describe your mash/sparge process (including how much water you used in each and how much ended up in the kettle pre boil)?

Grain bill was simple.

12 lb American- Pale 2-Row
1 lb Crystal 40

Mash at 154 for 60 minutes with about 20 quarts

Added 4 quarts of the hot sparge water (180 degrees) then drained into Kettle

Added 18 quarts of sparge water and let sit for 30 minutes before draining into the kettle- got 7.5 gallons into kettle.

Offline 69franx

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Re: Getting low OG.....?!
« Reply #4 on: May 16, 2016, 05:38:32 PM »
Just another thing to look at, was your 1.042 before or after your boil? Silly question I know, but plugging that grist into beersmith for my typical 6 gallon batches, I get 1.048 pre-boil estimate at 7.66g, down to 6g into fermenter at 1.056. Changing volume to 5g into fermenter, I get 1.056 down to 1.068. Your 7.5 g boiled down to 5g should yield 5g at 1.063.
Frank L.
Fermenting:
Conditioning:
In keg:
In Bottles:  
In the works: Hopefully brewing 10 gallons of Pilsner tomorrow for a family reunion in July, then back to IPA and  a barleywine to age

Offline blair.streit

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Re: Getting low OG.....?!
« Reply #5 on: May 16, 2016, 05:41:24 PM »

Grain bill was simple.

12 lb American- Pale 2-Row
1 lb Crystal 40

Mash at 154 for 60 minutes with about 20 quarts

Added 4 quarts of the hot sparge water (180 degrees) then drained into Kettle

Added 18 quarts of sparge water and let sit for 30 minutes before draining into the kettle- got 7.5 gallons into kettle.
Did you take pre and post boil gravity readings? I assume since you said OG that 1.042 was your post boil?

Offline dilluh98

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Re: Getting low OG.....?!
« Reply #6 on: May 16, 2016, 06:48:57 PM »
1/ Too coarse a crush on the grains. Probably number 1 culprit.

This was a big one for me until I started crushing my own grains. I'd get consistent mash efficiency for 3-4 batches and then all of a sudden I'd see a drop of 15-20%. As Denny has stated, "crush it until you're scared" or if you have your LHBS do it, tell them to crush it until they're scared.

Offline pete b

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Re: Getting low OG.....?!
« Reply #7 on: May 16, 2016, 06:54:42 PM »
My hunch is that the grains could be crushed more. Also, did you cool your wort to the temperature your hydrometer is calibrated to? Did you test your hydrometer for accuracy? It should be very close to 1.000 in water at the calibration temperature.
Do you really stir your mash in good, insuring no dough balls?
All these things can add up.
Don't let the bastards cheer you up.

Offline brewfreeordie603

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Re: Getting low OG.....?!
« Reply #8 on: May 16, 2016, 06:55:52 PM »
This was taken post boil, but I did take a pre-boil, which of course I don't have on hand right now.  I was really expecting to get much close to my numbers after this happened once already (as this time I was more diligent about temps, timing, and volume).

My grains were crushed at my local brew supply shop, and by all appearances look the way I have seen elsewhere.  I ended up using the spent grains to make a great bread, so they weren't so coarse that I couldn't eat them comfortably.  I will take that into consideration and ask for a finer crush next time (until I can assemble my own mill).

Offline HoosierBrew

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Re: Getting low OG.....?!
« Reply #9 on: May 16, 2016, 07:00:20 PM »
This was taken post boil, but I did take a pre-boil, which of course I don't have on hand right now.  I was really expecting to get much close to my numbers after this happened once already (as this time I was more diligent about temps, timing, and volume).

My grains were crushed at my local brew supply shop, and by all appearances look the way I have seen elsewhere.  I ended up using the spent grains to make a great bread, so they weren't so coarse that I couldn't eat them comfortably.  I will take that into consideration and ask for a finer crush next time (until I can assemble my own mill).




They probably won't be thrilled with being asked to adjust their mill grind finer. But they likely won't mind if you just ask them to double mill it (mill twice at their usual gap). I used to do that before I bought a mill - made a noticeable  difference.
Jon H.

Offline 69franx

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Re: Getting low OG.....?!
« Reply #10 on: May 16, 2016, 07:26:53 PM »
This was taken post boil, but I did take a pre-boil, which of course I don't have on hand right now.  I was really expecting to get much close to my numbers after this happened once already (as this time I was more diligent about temps, timing, and volume).

My grains were crushed at my local brew supply shop, and by all appearances look the way I have seen elsewhere.  I ended up using the spent grains to make a great bread, so they weren't so coarse that I couldn't eat them comfortably.  I will take that into consideration and ask for a finer crush next time (until I can assemble my own mill).




They probably won't be thrilled with being asked to adjust their mill grind finer. But they likely won't mind if you just ask them to double mill it (mill twice at their usual gap). I used to do that before I bought a mill - made a noticeable  difference.
+1, same experience here
Frank L.
Fermenting:
Conditioning:
In keg:
In Bottles:  
In the works: Hopefully brewing 10 gallons of Pilsner tomorrow for a family reunion in July, then back to IPA and  a barleywine to age

Offline denny

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Re: Getting low OG.....?!
« Reply #11 on: May 16, 2016, 08:26:52 PM »
1/ Too coarse a crush on the grains. Probably number 1 culprit.

2/ Volumes off - mash, sparge, preboil. Be sure to measure mash and sparge water accurately, account for grain absorption and dead space, and get an accurate boil off rate/hour on your kettle. This will help you hit your final volume into the fermenter accurately. If volumes are high or low, it affects your concentration of sugars and therefore your OG measurements.

3/ Temp accuracy - you need a thermometer that's accurate enough to hit your mash temp fairly accurately. If you unknowingly are mashing too high or too low, you could be outside the optimal enzymatic range for good conversion.

And to these I'll add not adjusting the recipe for you system's efficiency.  I think #3 is the least likely.  You'd have to be WAAAYYY off for that to matter.
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Offline HoosierBrew

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Re: Getting low OG.....?!
« Reply #12 on: May 16, 2016, 09:45:35 PM »
1/ Too coarse a crush on the grains. Probably number 1 culprit.

2/ Volumes off - mash, sparge, preboil. Be sure to measure mash and sparge water accurately, account for grain absorption and dead space, and get an accurate boil off rate/hour on your kettle. This will help you hit your final volume into the fermenter accurately. If volumes are high or low, it affects your concentration of sugars and therefore your OG measurements.

3/ Temp accuracy - you need a thermometer that's accurate enough to hit your mash temp fairly accurately. If you unknowingly are mashing too high or too low, you could be outside the optimal enzymatic range for good conversion.

And to these I'll add not adjusting the recipe for you system's efficiency.  I think #3 is the least likely.  You'd have to be WAAAYYY off for that to matter.


Agreed on #3.  1 and 2 were issues for me when I started. Easily enough fixed though!
Jon H.

Offline brewfreeordie603

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Re: Getting low OG.....?!
« Reply #13 on: May 16, 2016, 11:40:24 PM »
This is some good info, I appreciate the insight.  I'll pay close attention to these items during the next batch.  Thanks!

Offline MJK

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Re: Getting low OG.....?!
« Reply #14 on: May 18, 2016, 12:51:36 AM »
Might want to look at pH also. That's a pretty pale grain bill.

have fun