The First

[BKBrewer_4885]

Tried my hand at BIAB, looking at ways to improve my process. Any insights are much appreciated.
The Recipe Mosaic Smash Pale Ale on Brewers Friend
Water:3.8gallons Batch Size:2gallons Boil Gravity:1.032 Original Gravity:1.060 Final Gravity:1.011 ABV:6.46%

What I came out with
Water:3.75gallons Batch Size:approx 3gallons Pre-boil Gravity:1.030 @144.5 F Adjusted to:1.046
OG:1.044 FG:1.010 ABV calculated at 4.46%
My questions are what did I do wrong to get such a low OG? How do I calculate trub loss and grain absorption? Why is my batch size almost a full gallon higher than the intended recipe? Any other factors or details that I am missing?

Please Help, thanks.

 

[FatDragon]

Taking a gravity reading over 100 F is going to be way off to the point that correcting for temperature is really inaccurate. That's probably the source of the discrepancy between your measured pre-boil SG and OG. Your OG would be right on point if you boiled down to 2 gallons, so that's not a big issue.

The biggest issue is that you ended up with 50% too much wort. You can adjust for that by using less water from the beginning (though your efficiency will probably suffer by a few points) and/or boiling longer or harder to boil off more wort. Your boil-off rate, assuming you boiled for an hour, was about 3/4 of a gallon per hour. At that rate, you should have boiled for a little over two hours to get down to your intended volume, which would have concentrated the sugars to roughly at your intended OG.

If you find yourself in that kind of situation again, boil down to a reasonable volume before starting your boil clock and hop additions. So if you want to brew two gallons and you have four gallons of pre-boil wort, boil it down to three gallons and then start your hop schedule as if it just started boiling. Ideally though, take good brew notes and use them to adjust your water volumes and process until you've got everything dialed in to produce the right amount of pre-boil wort for your intended boil length and batch size. It'll probably take a few tries to get it hammered down, but you'll work it out.

 

[McKnuckle]

General guidelines for BIAB absorption: 0.12 gal/lb with gravity drain; 0.09 gal/lb with gentle squeeze or extended gravity drain; 0.07 gal/lb with aggressive, “get it all” squeezing.

Don’t forget to factor that in.

 

[Griffin495]

You need to understand your boil off rate. Looks like you used somebody else's from Brewer's Friend without knowing what your system actually is. Looks like you boiled off .75 gallons in an hour where as they boiled off 1.8gallons. You can fill your kettle up to 3.8 gallons (or whatever) and boil it for 30 minutes, measure how much you boiled off and multiply it by 2 to get how much your boil off rate is per hour. Then add that to your batch size (in this case 2) to get how much you should be starting off with pre-boil instead of their 3.8.

 

[CascadesBrewer]

What tool did you use to calc your values?

I use BeerSmith, but http://www.biabcalculator.com/ is decent for a simple calculator. You would need to adjust your batch values, your boil off rate, and you might need to adjust the Grain Absorption a bit (around 0.06 seems to work for me).

 

[BKBrewer_4885]

Thanks all for the great insight! I appreciate the help.

 

[BKBrewer_4885]

What tool did you use to calc your values?

I use BeerSmith, but http://www.biabcalculator.com/ is decent for a simple calculator. You would need to adjust your batch values, your boil off rate, and you might need to adjust the Grain Absorption a bit (around 0.06 seems to work for me).

I didn’t use any online calculators or software. Just saw a recipe and went for it. Thanks for the biabcalculator info.

 

[BKBrewer_4885]

What tool did you use to calc your values?

I use BeerSmith, but http://www.biabcalculator.com/ is decent for a simple calculator. You would need to adjust your batch values, your boil off rate, and you might need to adjust the Grain Absorption a bit (around 0.06 seems to work for me).

How did you figure out what your grain absorption? Is there a formula or a pre/post weight of the grains? Please let enlighten me

 

[doug293cz]

How did you figure out what your grain absorption? Is there a formula or a pre/post weight of the grains? Please let enlighten me

Grain absorption is easy to calculate. You measure both your strike water volume (the volume of water in your mash) and the volume of wort you collect after draining your mash (and any squeezing) before any sparging. The calculation for grain absorption rate is then:

Grain Absorption Rate = (Strike Vol - Collected Wort Vol) / Grain Bill Weight
​

To get the best accuracy, you should correct the volumes for thermal expansion (wort at mash temp has about 2% higher volume than wort at room temp.)

Brew on

 

[CascadesBrewer]

How did you figure out what your grain absorption? Is there a formula or a pre/post weight of the grains? Please let enlighten me

My first BIAB batch had 10 lbs of grain and I measured that I lost 0.5 gal due to absorption so 0.05...but 0.06 seemed to be giving me closer numbers. I crush my grain fine, so I think that reduces absorption and sometimes I will squeeze to get the volume I need. Note, on a batch with 3 lbs of flaked rye I noticed that I lost a lot more water, so you might need to tweak that value now and then (or just have a little extra water around that you can pour over your grain to add a little more water).

If you don't have the numbers from your first batch, a value around 0.1 might work well for store crushed grains. You can then monitor your volume and stop draining/squeezing when you have your target volume.

Was your 2 gallon batch size the amount into the fermenter? (That is what Brewer's Friend treats Batch Size as.) So for me that would look something like:

• Mash Water: 3.2 gals
  • minus 0.2 gal grain absorption
• Start of Boil: 3.0 gals
  • minus 0.8 gal boil off
• End of Boil: 2.2 gals
  • minus 0.2 gal kettle trub loss and temp shrinkage
• Fermenter: 2.0 gals
  • minus 0.3 lost in fermenter
• Bottle/Keg: 1.7 gals

You don't need precise number for each step, but a general feel of how much volume you need to start with to hit your target. Note that hops can suck up a lot of water, so you might have higher kettle and fermenter losses for highly hopped beers.

 

[wilserbrewer]

M
You don't need precise number for each step, but a general feel of how much volume you need to start with to hit your target.

This is a good point, sometimes for a beginner it can be overwhelming to calculate grain absorption, boil off, trub loss in fermenter, shrinkage due to temperature so on and so on.

Rather you can also simply look at your total starting water and finished beer amount and make adjustments to your starting water.

You don’t really care so much about individual losses, the sum total is what is most important.

 

[kh54s10]

This is a good point, sometimes for a beginner it can be overwhelming to calculate grain absorption, boil off, trub loss in fermenter, shrinkage due to temperature so on and so on.

Rather you can also simply look at your total starting water and finished beer amount and make adjustments to your starting water.

You don’t really care so much about individual losses, the sum total is what is most important.

I agree with this, but would add that you DO need to know boil off. A lot of people only boil off 3/4 gallons per hour. My burner sputters if I turn it too low so my boil off is 2 gallons per hour.... You need to find out what that is.

I use a mash tun so squeezing doesn't factor into the equation. I don't pay any attention to trub loss, shrinkage etc (I set those in my equipment profile in Beersmith though.) I know that if I want 5.25 gallons into the fermenter I need to collect right about 7.25 gallons preboil.

I sparge, so I use 1.3 quarts per pound of grain. Collect the preboil then batch sparge with enough to collect the proper preboil.

BIAB - you can do full volume where you have to calculate more accurately or you could sparge to get to preboil.

Low OG is most often traced to a bad crush. With BIAB - crush finer.

 

[wilserbrewer]

I agree with this, but would add that you DO need to know boil off.

Either I am confused or just more care free than most here....

If I know my total losses, I don’t really care if it is from boil off, trub loss or grain absorption....

Of course with the exception on larger grain bills my losses will increase slightly.

I don’t really have a clue what my boil off is “off hand”, but I have a real good idea that I need to start w/ X to finish w/ Y.

Why is it so important to know the parts of the sum when the sum is what matters?

 

[kh54s10]

Well, you actually do know your boil off even if not in % or gal/hr. My boil off was adjusted in my Beersmith equipment profile years ago. I don't actually pay that much attention. I brew with with a 3 vessel rig and I use the strike amount BS tells me, then I measure, and sparge with 1/2 of what I need to preboil and a second sparge to more accurately hit preboil volume. Part of this is so that the spent grain is mostly drained and lighter. When I BIAB, I do smaller batches and try to get 3 gallons into the fermenter. I don't really try to hard to get it right on. 2.75 or 3.25 are not worth worrying about except 3.25 is likely to blow off quite a bit.

 

[BKBrewer_4885]

All really good insights. Another question if I may, how do you figure out trub loss?

 

[kh54s10]

All really good insights. Another question if I may, how do you figure out trub loss?

I don't really. I know that there will be a little in primary, usually only a little so I start with a little over 5 gallons in the fermenter to get 5 gallons packaged. Unless you are making really hoppy beers there won't be much in the kettle and really, all of that can go into the fermenter if you wanted. For really hoppy beers I use a 5 gallon paint strainer bag clipped to the lip of the pot to contain the hop debris. I only leave about 1/4 inch in the bottom of my kettle unless I am short on fermenter volume. If that happens I pour it all into the fermenter. When I dry hop I collect more wort into the fermenter to account for that. Amounts are just by eye, a little more sparge, a little more left after the boil.

For full volume BIAB just start with a little more water. How much? It depends on recipe amount of hops etc. No set amount will work all the time.

 

[CascadesBrewer]

All really good insights. Another question if I may, how do you figure out trub loss?

The easiest way...when you get done transferring your wort into the fermenter, pour the remaining amount in your kettle into a pitcher and measure it. You might lose volume in hop bags/spider as well if you use them. The same general idea applies to fermenter loss, though I have some marking on the side of my fermenter so I can eyeball it.

For me I have figured out that for a "normal" beer I lose about 0.75 gal between kettle trub and fermenter loss. I lose more for heavily hopped beers. In my BeerSmith profile I have 0.25 kettle loss and 0.5 fermenter loss, but it is not critical exact values on each side. If you dump the entire contents of your kettle into the fermenter you might have 0 loss at that point, but it will settle out and you will have more loss in the fermenter.

For a long time I thought that 5.25 gal into the fermenter would get me 5.0 into a keg...until I started to measure my keg volume (using a scale) and realized I was actually only getting around 4.75 gal into the keg.

 

[BKBrewer_4885]

The easiest way...when you get done transferring your wort into the fermenter, pour the remaining amount in your kettle into a pitcher and measure it. You might lose volume in hop bags/spider as well if you use them. The same general idea applies to fermenter loss, though I have some marking on the side of my fermenter so I can eyeball it.

For me I have figured out that for a "normal" beer I lose about 0.75 gal between kettle trub and fermenter loss. I lose more for heavily hopped beers. In my BeerSmith profile I have 0.25 kettle loss and 0.5 fermenter loss, but it is not critical exact values on each side. If you dump the entire contents of your kettle into the fermenter you might have 0 loss at that point, but it will settle out and you will have more loss in the fermenter.

For a long time I thought that 5.25 gal into the fermenter would get me 5.0 into a keg...until I started to measure my keg volume (using a scale) and realized I was actually only getting around 4.75 gal into the keg.

Gotcha!! Thanks for the information.

 

[CascadesBrewer]

Gotcha!! Thanks for the information.

Honestly it can be as simple as "I started with 7 gals of mash water and only got 4.5 gals into the keg...so I need to start with 7.5 gals to get 5.0 gals into the keg". If using a program like BeerSmith, add that loss into whatever step seems the most reasonable.

I don't micromanage my losses and I don't measure them each batch or change them in BeerSmith for each batch. I know hoppy beers will suck up some beer, so I will probably end up with a little less volume in my keg.

I do try to hit my pre-boil volume since that volume is key to hitting the other volumes. I stop my bag draining when I have the needed volume and squeeze if I need more volume (or sparge with some filtered/distilled water if I am too low). When I fly sparged, I sparged until I hit the target volume.