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Old 12-11-2012, 12:34 PM   #1
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Default Question about low OG reading

I brewed a batch this weekend and the recipe called for an OG reading of 1.062, and mine came in at 1.050. I have a suspicion why, and want some feedback.

I cooled the wort to 68 degrees, then whirlpooled and let it sit for about 30 min. I drew my sample from the "clear" wort on top after all the solids settled at the bottom of the pot.

Maybe I should have taken the sample before whirlpooling. Could my low OG reading be due to a bad sample?

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Old 12-11-2012, 01:21 PM   #2
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Was this extract or all grain batch. If its extract its probably a poor dilution of extract and top off water in your sample. If its all grain it's likely it would be a poor crush on the grains. At least in my experience.

With extract recipes. As long as you are sure in your volumes you can pretty much rely on the OG specified in the recipe that that's what you will end up with.

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Old 12-11-2012, 01:32 PM   #3
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What volume was the recipe OG (1.062) based on? And what was your kettle volume after the whirlpooling? Everything should have been well mixed with homogenous temperature if it whirlpooled then sat for 30 min...That large of a discrepancy leads me to volume differences.

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Old 12-11-2012, 02:02 PM   #4
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Originally Posted by helibrewer View Post
What volume was the recipe OG (1.062) based on? And what was your kettle volume after the whirlpooling? Everything should have been well mixed with homogenous temperature if it whirlpooled then sat for 30 min...That large of a discrepancy leads me to volume differences.
It was a 2.5 gallon recipe, all-grain, BIAB. I did not take a reading of the kettle volume after whirlpooling, but I had about 3 gallons racked to carboy after leaving probably .5 gallons of "gunk" in the bottom of the kettle. My thought was after trub-loss, racking losses, etc...that I will end up with 2.5 gallons in the bottling bucket.

I had suspected I may have used too much water. I've been trying to get the bugs worked out of my system. This is about my 10th all-grain BIAB batch I've brewed, and I always end up with too much, or not enough wort.

I've done tests and determined my boil-off rate to be 1.15 gal/hour. I'm now trying to account for other variables so I can get my starting water volume correct.
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Old 12-11-2012, 02:22 PM   #5
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Here's the recipe btw...

Conway's Irish Ale Clone

Batch Size: 2.5 gallons
OG: 1.062
FG: 1.017
SRM: 13°
IBU: 24.4
ABV: 6.0%

Grain Bill:
5 lb Pale 2-Row
4 oz Crystal 80L
4 oz Victory
2 oz Special B
2 oz Biscuit

Hops:
¼ oz German Northern Brewer 9.6% - 60 min
½ oz German Hallertau 4.3% - 10 min
¼ oz Fuggles 4.8% - 5 min

Other:
1 tsp Irish Moss – 15min
4 oz Maltodextrin – 15 min

Mash 90 min @ 153°F
Mash Out 10 min @ 170°F
Boil 60 min

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Old 12-11-2012, 09:13 PM   #6
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If you over shot your wort volume by .5 gallons or more then your OG will be less due to dilution. You could have continued the boil to remove the remaining .5 gallon you had.

BIAB brewing from what I understand delivers a little less efficiency and has greater dependence on the crush of the grain as well. It's my understanding that BIAB brewers try to get a very fine crush to make up for this deficiency so IMO that would be the first thing to look at as well as the calculation of your volumes.

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Old 12-12-2012, 10:33 AM   #7
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Originally Posted by duboman View Post
If you over shot your wort volume by .5 gallons or more then your OG will be less due to dilution. You could have continued the boil to remove the remaining .5 gallon you had.

BIAB brewing from what I understand delivers a little less efficiency and has greater dependence on the crush of the grain as well. It's my understanding that BIAB brewers try to get a very fine crush to make up for this deficiency so IMO that would be the first thing to look at as well as the calculation of your volumes.
That is my understanding as well. I have been relying on various LHBS and online vendors to crush my grains for me, so my efficieny keeps changing from batch to batch. However my corona mill is scheduled to arrive on my doorstep tomorrow so I will start crushing them myself to become more consistent.

This batch I did get high efficiency though, I measured it at 83.5%.
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Old 12-12-2012, 03:58 PM   #8
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Originally Posted by happypanties View Post
That is my understanding as well. I have been relying on various LHBS and online vendors to crush my grains for me, so my efficieny keeps changing from batch to batch. However my corona mill is scheduled to arrive on my doorstep tomorrow so I will start crushing them myself to become more consistent.

This batch I did get high efficiency though, I measured it at 83.5%.
One thing I forgot to mention: The efficiency numbers you are looking at, are they the total brewhouse or mash/lauter? THere is a difference and can help you closer evaluate what is going on. If you get a good number with your pre boil then you know your mash is converting well and you are doing a good job on that end.

If your total efficiency number is not where you want it to be then you need to look at your volumes and losses, boil off and what goes into the primary as that is where your efficiency is dropping.
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Old 12-12-2012, 09:32 PM   #9
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It would be lauter efficiency then. I take my readings after I mash-out, drain grains (including squeezing the bag), give the wort a good stirring, take my sample and check wort volume, and use this calculator:

http://www.brewersfriend.com/brewhouse-efficiency/

I think in this case I used too much strike water. I'll get this nailed down, it just might take some more brewing to get it all worked out!

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