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Can't seem to hit my OG target

BeerNut

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Hi fellow brewers.

I have been trying to brew a BIAB recipe I developed and after two tries I still come out way too low on the OG.  My target is 1.053, but I always float around 1.040.  I can't figure out why I am always so low.  I am mashing at 158.5 for 90 minutes.  My grain bill is

5 lbs 2 row
1 lb flaked corn
.5 carapils
.25 victory malt

Batch target volume 3 gallons.  Any ideas?  I have brewed several small BIAB's and never had this problem.
 

Oginme

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A few more questions to clarify your actual efficiency:

How much are you actually putting into the fermentor?
How much do you have left over (trub loss)?

Just from a rough calculation, it appears as though the recipe is designed for around 65% efficiency and you are getting somewhere in the neighborhood of 50%.

Things to look at:

1.  Check your thermometer for accuracy. 
2.  IMO, you are mashing sort of high, especially for the amount of non-malt adjuncts you have (1# of flaked corn).  You may want to try a lower mash temperature once you have your thermometer calibrated.
3.  If you have a lot of wort left over that does not make it into the fermentor, you should cut down on the volume of water you are using to mash.
4.  When you add your grains to the bag, stir like your life depends upon it.  If you are getting dough balls, it will cut down on your efficiency very quickly.  I typically stir for at least 3 to 5 minutes and longer if I see small clumps of grain on my mashing spoon.

I would start by trying a simple recipe (base grain + 1 or 2 specialty malts, no adjuncts) to get my efficiency in line.  Measure everything at each step (volume, specific gravity, temperature) so that you can tune in your equipment profile.

 

BeerNut

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Yes the recipe is for three gallons and I am fermenting three gallons.  My thermometer is ok and I hit my numbers when I'm not using the corn.  Never had a problem before. 
 

ihikeut

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When using corn in a recipe, it's recommended to use some 6 row. I'm not a expert but have read that 6 row has more of one enzyme  to extract sugars from the corn.
 

BugHunter

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If you want to increase your efficiency with biab, do your mash with a portion of your water but leave some out.  Then 'sparge' by using the balance of your clean water a second time.  Move your wort to another container.  Heat the balance of the water to 168, rinse your grains well with it and add it to the kettle.  You'll pick up quite a few points of efficiency.

You could also just assume you'll get 50% and add grain accordingly.
 

MY ADV

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I agree, double the grind. No need to worry about a stuck mash.
 
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