Grain absorption and boil off numbers for 2.5 gal batches

[Kenmoron]

I’m pretty new to homebrewing and am now 2 batches in to BIAB. I use a 5 gal kettle and am doing full volume, no sparge batches of usually 2.75 gal into the fermenter (roughly 2.5 gal bottled). I was wondering if anyone else is doing something similar and what their grain absorption and boil off numbers look like. My grain absorption is about 0.045 gal/lb and boil off is about 0.5 gal/hr. My numbers seem really low compared to most of what I’ve seen out there. I boil on my stove and my kettle has a diameter of about 11.5 inches. I’ve had to change a lot of parameters in BeerSmith to get my recipes dialed. Current efficiency is about 75%. Am also considering adding a fly sparge to try to bump that up though.

 

[SanPancho]

I do similar sizes, but typically 3 or 3.5.

boil off is obviously variable, but for home-brew it seems to be optimal to get to a boil to have decent hot break, then drop to a rolling simmer. in pro systems the goal is 10-15% boiloff, but kettle design is different there. basically, after you get the hot break, be gentle and don't try to boil off too much.

as for absorption, it depends on whether you squeeze. I go at it like a 14 year old and his first set of boobies. others just let it drain.

I used to do batch sparge. a lot easier than fly sparge. I could get up to 80% that way. I now do overnight mashing since I got a kid and pregnant wife and tons of projects going on 24/7. without trying I get 80% at full volume. and I can wake up and have the boil and chill done in about 2.5 to 3.5 hours, depending on if I do whirlpool, hop stands, etc.

my overall advice is to not chase a few points just for the sake of chasing points. guys are constantly saying "grain is cheap" and in reality, it is. lots of sparge means lots of boiloff, lots of time, etc. etc. be ok with a happy medium. find a system that works for you and stick with it. as long as the numbers are decent then just accept it and stick to a routine. a lot easier to make good beer that way.

 

[McKnuckle]

I also brew 3 gallons and under, usually 2.6 to fill a 2.5 gallon keg.

I have a 14" kettle, and my evaporation is 0.86 gal/hr. Yours will be much less, and I had similar results when I used a 5 gallon kettle on the stovetop.

I do BIAB, and gravity drain but do not squeeze, which gets me 0.12 gal/lb absorption. When I have squeezed in the past, I did it firmly but not aggressively, and averaged around 0.08 gal/lb absorption. I know it can go lower but I stopped that practice altogether. I would not be surprised with 0.045 if you are busting that bag.

Seems like your numbers are perfectly normal.

 

[CascadesBrewer]

My grain absorption is about 0.045 gal/lb and boil off is about 0.5 gal/hr. My numbers seem really low...Current efficiency is about 75%. Am also considering adding a fly sparge to try to bump that up though.

Your absorption number is about what I use (I plug in 0.05 gal/lb...0.4 fl oz/oz in BS3 Mobile). I am working to tune my boil off rate on my gas stove, but around 0.7 or 0.8 gal/hr seems right for me (my propane burner gets 1.0 to 1.5 gal/hr depending on how high I set it). 75% overall efficiency is pretty decent for a full volume mash. That is the number I have been using. A fine grain crush will help efficiency if you crush your own grains. I have been doing a dunk sparge on my 5 gal batches outdoors, but when I played around with a sparge on stovetop batches, it was just too much of a pain (spilling sticky wort on my floor and on my stove).

 

[Leezer]

Your numbers sound similar to mine. I do full volume no sparge biab, 4G kettle, 2 to 2.5G batches. My boil off is consistently 0.5G per hour on my kitchen stove. I lose between 1/8 to 1/4 of a gal to grain absorption, depending on how much I squeeze.

 

[VirginiaHops1]

I do 2.5 gallon BIAB stovetop batches in a 5 gallon kettle. My boil-off is slightly under 1 gallon an hour. After a few batches dialing in my numbers I find what works is a starting water volume of about 4.25 gallons, although I can't fit it all in my kettle to mash. After absorption and boil-off that usually gets me what I want into the fermenter.

I have been working with pretty bad efficiency and using a lot of grain, but have my own grain mill now so may have to re-tweek numbers if my absorption changes significantly with using less grain. It seems like everyone's systems are slightly different so really the only way to dial in your numbers perfectly is just doing batches and taking good notes.

 

[Griffin495]

I do 2.75 g batches into the fermenter to get 2.5g batches bottled losing a qt to trub. My boil off rate on my gas stove is 0.5 gallons and my absorption n is 0.05 so you numbers are close to mine. I crush my own grain and hit 78%

 

[Kenmoron]

Ok so it sounds like I'm on the right track and some people are having pretty similar numbers to mine. My potential sparge would be to hold back about a half gallon or so, and once the mash is complete rinse the grains with that much hot water straight from the tap (I have really soft water). Not sure how much of a bump in efficiency that would be, if any. But I guess I won't try to hard.

In regards to grain crush though, I do not have my own mill. My LHBS has a self-mill setup where you crush your own grains. I usually just run it through that thing twice. How about 3 times?

 

[McKnuckle]

The problem with crushing multiple times is perhaps a bit obvious: If the first crush breaks the grain into pieces smaller than the gap, then the next time they will just pass through the gap untouched. Yes, you will get random bits that crush smaller simply because they fall into the gap in a different orientation, or are pressed up against other pieces. But it's very much diminishing returns.

I would ask if the mill can be adjusted, or just accept your current efficiency. 75% mash or brewhouse efficiency is not an issue at all. 75% conversion efficiency on the other hand; I'd seek to improve that. But you don't specify in this thread.

 

[Kenmoron]

The problem with crushing multiple times is perhaps a bit obvious: If the first crush breaks the grain into pieces smaller than the gap, then the next time they will just pass through the gap untouched. Yes, you will get random bits that crush smaller simply because they fall into the gap in a different orientation, or are pressed up against other pieces. But it's very much diminishing returns.

I would ask if the mill can be adjusted, or just accept your current efficiency. 75% mash or brewhouse efficiency is not an issue at all. 75% conversion efficiency on the other hand; I'd seek to improve that. But you don't specify in this thread.

My ‘mash’ efficiency is at 75% using the double crush method. I know that there’s additional crushing involved and not just grain falling through because it won’t move through the mill without turning it on...and stopping the mill results in the grain not moving. Just wasn’t sure if successive passes through the mill would get me closer and closer to a finer crush without doing something negative. I’ll have to look into the adjustment of the mill...but I’m pretty sure it’s at a set width.

 

[Cato1507]

I’m pretty new to homebrewing and am now 2 batches in to BIAB. I use a 5 gal kettle and am doing full volume, no sparge batches of usually 2.75 gal into the fermenter (roughly 2.5 gal bottled). I was wondering if anyone else is doing something similar and what their grain absorption and boil off numbers look like. My grain absorption is about 0.045 gal/lb and boil off is about 0.5 gal/hr. My numbers seem really low compared to most of what I’ve seen out there. I boil on my stove and my kettle has a diameter of about 11.5 inches. I’ve had to change a lot of parameters in BeerSmith to get my recipes dialed. Current efficiency is about 75%. Am also considering adding a fly sparge to try to bump that up though.

That's about what I get on my 5.5 SSBrewtech kettle. That's not a bad efficiency to me. I get that on a single crush on my BC mill with no sparge just squeezing.
If I double crush the efficiency seems to jump way up, but it's resulted in higher ABV than I wanted on a couple of brews.

I'm sure I could chart that and dial back on my grain to bring it in line, but I haven't pursued it because in my 2.5 to 5 gal max batches it's not that much difference in grain cost to concern me. I'm happy just hitting my numbers in BS for both my kettle and fermenter profiles in BS.

 

[Cato1507]

I do similar sizes, but typically 3 or 3.5.

boil off is obviously variable, but for home-brew it seems to be optimal to get to a boil to have decent hot break, then drop to a rolling simmer. in pro systems the goal is 10-15% boiloff, but kettle design is different there. basically, after you get the hot break, be gentle and don't try to boil off too much.

as for absorption, it depends on whether you squeeze. I go at it like a 14 year old and his first set of boobies. others just let it drain.

I used to do batch sparge. a lot easier than fly sparge. I could get up to 80% that way. I now do overnight mashing since I got a kid and pregnant wife and tons of projects going on 24/7. without trying I get 80% at full volume. and I can wake up and have the boil and chill done in about 2.5 to 3.5 hours, depending on if I do whirlpool, hop stands, etc.

my overall advice is to not chase a few points just for the sake of chasing points. guys are constantly saying "grain is cheap" and in reality, it is. lots of sparge means lots of boiloff, lots of time, etc. etc. be ok with a happy medium. find a system that works for you and stick with it. as long as the numbers are decent then just accept it and stick to a routine. a lot easier to make good beer that way.

+1, I Completely agree.