Not Hitting OG in my BIAB

Northshore

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After a 15 year hiatus from homebrewing I am getting back into the hobby. I used to do full volume extract brewing but now I am trying my hand at BIAB. I have about 10 batches under my belt and I am trying to dial in what to expect with efficiencies from my setup. Unfortunately, they have been all over the map and I am hoping someone can steer me in the right direction.

Just this week I did a 2.5 gallon version of Braufessor's NEIPA. I had increased the grain but kept the percentages the same and was shooting for 1.065 as my OG but ended up at 1.050. Most of my other batches missed the targeted OG by about .003 points but this is by far the biggest miss I have had since trying BIAB. My pre-boil volume and post boils volumes were pretty spot on. From my brew session:

Efficiency
Conversion: 85%
  • Pre-Boil: 67% 24.1 ppg
  • Ending Kettle: 58% 21.2 ppg
  • Brew House: 55% 20.1 ppg
On average, I have been getting in the low 60's for brewhouse efficiency. Any tips on how to improve that?
 
Accepting I'm not an expert... :)

My preference is for English style pales between 3.5 and 5.3% ABV. In those parameters my efficiency comes in at 85% really consistently. What I find is that when I go beyond that 5.5-6% ABV I get into seriously diminishing returns and the efficiency dips way down, trying to persuade an Imperial stout to finish above 8% takes a lot of grain and a long old boil.

I've found that careful attention to (particularly) strike/mash temp really helped with efficiency. I also found that a yeast that I trusted was helpful as well so stick to S04 and US05 exclusively now.

All that said, a miss of 15 points is pretty substantial. Is that using the recipe tools here?
 
Your PPG shouldn't go down between pre-boil and post-boil. You can't lose sugar during boil, only water. You've got a measurement error somewhere. I never trust pre-boil measurements, personally and always assume that the only number that's inarguable is an accurate measurement of gravity and volume post boil and cooled to proper temp.
 
For BIAB, I adjusted my grind on the grain for a finer grind. I also do not do a full volume mash. I remove and drain the grain bag at the end of the mash and then do somewhat of a batch sparge on the grain bag. This keeps me in the 75-78% brew house efficiency range, which is pretty good for BIAB.

I have noticed that the higher the OG, the lower the efficiency.
 
Have you tried mashing longer? The guys over in OZ that helped pioneer BIAB swear by a 90 minute mash.
 
Your extract and pre-boil efficiency looks good for a recipe with 70% efficiency after the boil. If your pre-boil numbers are too low I'd be looking at too much water as the problem.

As JA says there's something weird happening with the pre and post boil numbers. They should only be off by measuring errors. That'd be my first focus.
 
Sorry for the delayed response. I drafted a reply over the weekend and apparently never posted it so here it is:

@Steve SPF , Yes, I do use the recipe tools here on the site. After doing some reading, I am finding that I might have had a few things going against me. I brew outside and it was 45 (F.) on brew day. I followed the strike water calculator here on Brewer's Friend which suggests adding 10 degrees to the strike temperature for cold weather brewing. I did that but that overshot my needs by a lot. I was up around 164 degrees after doughing in. After stirring with the lid off, removing the grain bag and stirring more, I eventually got down to my 152 degree target. I did have to reheat a coupe times during the 60 minute mash as well to maintain temp. I am guessing that with all the fiddling around during this time I lost some points. I suspect I did not even get the full 60 minutes with all the fussing either.

After reading elsewhere and as mentioned above by others, the other issue could be grain crush. Even on batches prior to this I have never done better than 70% brewhouse efficiency. I order my ingredients from MoreBeer! and while they have told me that their mill is okay for BIAB, I am suspect that a finer crush would be better. A new homebrew shop opened near me so I will try them next time and double crush the grain. I may also introduce some method of a sparge and see if that buys me some efficiency. I squeeze the life out of the bag already but I know there are sugars still lurking in there. Any recommendations on sparge techniques for BIAB? Dunk the grain bag in a couple gallons of water that would normally be in the mash?
 
That's an interesting point. I went back and checked a couple other brew sessions only to find similar issues. Maybe I need new glasses?

On this batch, I tested out a new (and cheap) analog refractometer which may have been a contributor to erroneous data. I have since read that you need to see what the correction factor is on the device. Over the weekend I followed the guidance here and mixed up a batch of 1.080 wort. As the article suggested, my readings varied depending on the sample. After 6 samples my correction factor was a whopping 1.057!

Your PPG shouldn't go down between pre-boil and post-boil. You can't lose sugar during boil, only water. You've got a measurement error somewhere. I never trust pre-boil measurements, personally and always assume that the only number that's inarguable is an accurate measurement of gravity and volume post boil and cooled to proper temp.
 
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Any recommendations on sparge techniques for BIAB? Dunk the grain bag in a couple gallons of water that would normally be in the mash?
I pull the bag out of the kettle and let it drain and give it a couple of good squeezes. I then look at the marking in the kettle and see how much more liquid I need for the starting boil volume.

I put the grain in bag in a bucket and add that amount of water (150 degrees or so). I stir it around a couple of minutes and lift the bag, drain it, squeeze it, and pour the liquid into the kettle. I find that it is a pretty sugar rich solution, so it does increase the efficiency a bit.
 
My last couple batches have been 2.5 gallons which allows me to experiment and not blow loads of money on expensive hops for failed experiments. Brewers Friend called for 5.4 gallons in my mash kettle. Just for kicks I tried Priceless Brewing and Simple BIAB's water volume calculators. None were exact but they were all within a half of each other. Is there any science behind how much water is needed in the mash vs. the sparge with BIAB?

I pull the bag out of the kettle and let it drain and give it a couple of good squeezes. I then look at the marking in the kettle and see how much more liquid I need for the starting boil volume.

I put the grain in bag in a bucket and add that amount of water (150 degrees or so). I stir it around a couple of minutes and lift the bag, drain it, squeeze it, and pour the liquid into the kettle. I find that it is a pretty sugar rich solution, so it does increase the efficiency a bit.
 
My last couple batches have been 2.5 gallons which allows me to experiment and not blow loads of money on expensive hops for failed experiments. Brewers Friend called for 5.4 gallons in my mash kettle. Just for kicks I tried Priceless Brewing and Simple BIAB's water volume calculators. None were exact but they were all within a half of each other. Is there any science behind how much water is needed in the mash vs. the sparge with BIAB?
I always make 2.5 gallon batches. This usually equates to 5-6 pounds of grain. So I use about 10 quarts of water in the mash, a 2.0 qts/lb. ratio. After the mash, I lift the bag and drain. There's usually somewhere around 2 gallons in the brew pot at this point. I set the bag in a bucket and add about 1.5 gallons of hot water. I stir it pretty well for a minute or two. I then lift the bag and drain and pour the remaining into the brew pot. I then have about 3.5 gallons of wort. After the boil, I end up transferring about 3 gallons to the fermenter.

Keep in mind that none of this is exact (and it doesn't need to be). Experiment with your equipment setup and you'll probably want to adjust this a bit. But it's a reasonable place to start.
 
That's an interesting point. I went back and checked a couple other brew sessions only to find similar issues. Maybe I need new glasses?

On this batch, I tested out a new (and cheap) analog refractometer which may have been a contributor to erroneous data. I have since read that you need to see what the correction factor is on the device. Over the weekend I followed the guidance here and mixed up a batch of 1.080 wort. As the article suggested, my readings varied depending on the sample. After 6 samples my correction factor was a whopping 1.057!
Wort color makes a big difference too. If you'd mentioned that they were refractometer readings, I'd have told you right away that that was the problem. Use a hydrometer when you have any doubts about the actual number. :)
 
...and take refractometer claims of "Automatic Temperature Correction" with a grain of salt. Cheap refractometers (under $100 or so) don't do this well. (1.057 correction? Absurd*. That's over 100% error!)

A hydrometer is rarely off, assuming wort temperature is correct.


*(I don't mean YOU are absurd. The instrument is being absurd)
 
I find if you wait 30 seconds with a refractometer it cools anyway. I just take a reading and let it sit a couple minutes.
 
I find if you wait 30 seconds with a refractometer it cools anyway. I just take a reading and let it sit a couple minutes.
I keep a cup of cool water handy to cool the sample in the bulb end of a pipette
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That would also work I imagine.
 
I do the same as Craig, and then I use the water to calibrate so that the samples are near similar temperatures.
 
...and take refractometer claims of "Automatic Temperature Correction" with a grain of salt. Cheap refractometers (under $100 or so) don't do this well. (1.057 correction? Absurd*. That's over 100% error!)

A hydrometer is rarely off, assuming wort temperature is correct.


*(I don't mean YOU are absurd. The instrument is being absurd)
Actually that's not terrible as a wort correction factor - mine's at 1.04. The ATC, that's normally more applicable to pH meters - the mass of the prism compared to the sample (a couple of drops of liquid) cools the sample so quickly temperature correction is generally not needed. I agree that a hydrometer is generally accurate, but you'll pry my refractometer from my cold, dead hands!
 
For the $18 I spent on this thing, throwing it in the trash won't be that hard if it proves to be more trouble than it is worth. I do plan on running it through its paces on my next batch alongside my hydrometer. This tool is not the root of my batch inefficiency problems though; I am tracking 4.6% ABV right now - a session IPA, a term in itself which is an oxymoron!
 

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