BIAB recipe adjustments

[DanInSydney]

I’m making the jump from malt extracts to BIAB and for my first brew I plan to keep it as easy as possible - full volume mash technique (no sparging)

But I keep reading lots of conflicting info on how much water I should plan to use for my pre boil volume. If I’m following a ‘standard’ recipe, how do I allow for evaporation etc?

 

[kh54s10]

Evaporation is differed slightly to greatly depending on your pot geometry, pot material, heat source, ambient temperature, local humidity. There is no set answer. You could boil a pot of water for 15 minutes then check the loss. Then multiply that number by 4 to get the boil off for an hour boil.

An often cited starting point would be 3/4 gallon per hour.

Grain absorption also has to be accounted for but is tricky with BIAB if you squeeze out the wort from the grain.

 

[McKnuckle]

Some good assumptions for BIAB absorption are: Full gravity drain (no squeeze) until the boil is ready, is about 0.09 gal/lb. A brief, light squeeze gets you 0.08 gal/lb, and an aggressive squeeze maybe 0.06 gal/lb.

For evaporation, as kh54s10 said, it varies widely. 0.5-1 gallon/hr is common, depending on the variables listed above. I usually do a test run with water for a full hour after acquiring a new boil kettle.

 

[MikeCo]

Evaporation can be controlled to some extent by how vigorous the boil is. I set my burner or element just high enough to get a gentle boil. For a 5-gallon batch in a 10 gallon kettle I get around 0.9 gallon per hour boil-off. A kettle with a larger diameter for a given batch size will generally see more boil off also. If you find half way through your boil you are getting too little or too much boil off, you can adjust the burner or element to compensate.

When I started BIAB, I used the default in BeerSmith for BIAB grain absorption (0.586 fl oz/oz) but found it was too high since I squeeze the bag. Currently I have it set at 0.465 fl oz/oz. I arrived at this number after recording the absorption after several batches and taking an average. I calculated absorption by subtracting the post-mash volume from total water volume. The absorption varies by grain weight and the amount of squeezing.

My pre-boil volume for a 5.5 gallon batch is around 6.8 to 7 gallons. That leaves me around 6 gallons after boiling. With trub and hop absorption, that gets me close to my target of 5.5 gallons in the fermenter, often slightly more.

I recommend measuring absorption, boil-off and other losses for your first few batches after starting with your best guesses so you can correct for subsequent batches. You need to know these for your own system and process to hit your numbers exactly, and it's a learning process.

You'll still have good beer even if your volumes are a little off the first batch or two.

 

[RM-MN]

I’m making the jump from malt extracts to BIAB and for my first brew I plan to keep it as easy as possible - full volume mash technique (no sparging)

But I keep reading lots of conflicting info on how much water I should plan to use for my pre boil volume. If I’m following a ‘standard’ recipe, how do I allow for evaporation etc?

Good advice from the above but first, RDWHAHB. In other words, don't worry about it. If you boil off too much water, it's just water so add some back if you are short of the volume you want. If you have too much water you can boil longer or......just be thankful for the extra beer.

 

[Bobby_M]

I’m making the jump from malt extracts to BIAB and for my first brew I plan to keep it as easy as possible - full volume mash technique (no sparging)

But I keep reading lots of conflicting info on how much water I should plan to use for my pre boil volume. If I’m following a ‘standard’ recipe, how do I allow for evaporation etc?

You can't really take anyone's advice as gospel. You just have to go for it and take notes along the way to learn all your losses give your process and equipment. Losses to grain absorption is going to depend on how hard you squeeze. Losses to boil off depend on how hard you boil and all that. Losses to kettle trub depend on whether you bag your hops or how much trub you want to leave out of the fermenter.

For 6 gallons in the fermenter, I start with approximately 8.25 gallons of water assuming about 14 pounds of grain. You may want to start with 8 gallons and then take very good notes on how much wort you derive preboil, post boil and finally in the fermenter. Use that data for the next brew.

 

[DanInSydney]

Great advice guys, thanks! I think these are some good guidelines for my first attempt, then I should hopefully understand my ‘system’ with time.

How do you go about measuring boil off when your contents are still in the pot?! I don’t have any internal measurement markers on mine...

 

[Chorgey]

I came across this link that 'might help' in calculating boil off, based on your kettle's width

https://www.homebrewtalk.com/forum/threads/brewing-calculators.621343/#post-7919267

Cheers!

 

[lowtones84]

Great advice guys, thanks! I think these are some good guidelines for my first attempt, then I should hopefully understand my ‘system’ with time.

How do you go about measuring boil off when your contents are still in the pot?! I don’t have any internal measurement markers on mine...

This is a kind of stupid method, but it's what I used to do. Got a dowel (if you have a wooden mash paddle this could work too) and cut in marks for 1 gallon, 2 gallons, etc. Now it will only work for the pot geometry, but...

 

[McKnuckle]

Depending on how dedicated you are, here's a way to determine how much post-boil wort was produced. If you know your pre-boil volume, you can then use subtraction to figure out how much evaporated.

1) Chill the wort
2) Tare your fermenter (weigh it empty), and note the weight in kilograms
3) Get your chilled wort into the fermenter
4) Weigh the full fermenter, and subtract the tare value to get the wort weight
5) Take a gravity sample to determine OG
6) Divide the wort weight by the OG. This is the volume of water in your fermenter in liters.

Now repeat these steps for any remaining wort you left in the kettle, using a different tared vessel of course. Add the two volumes together to get the total amount of wort produced.

Now just subtract that from the pre-boil volume, and there's your evaporated volume. Divide this value by 3.785 to get the equivalent in gallons.

Yes, sticklers will point out minor inaccuracies with this approach, but it's quite a bit more precise than visual volume markers on a kettle wall.

 

[iamwhatiseem]

Don't worry about it.
Unless you are brewing for competition etc.... why worry? Just enjoy the process.
In the end, if two people brewed the exact same beer... one had 5.2 gallons, one had 4.8... the only way you could tell the difference is with instrumentation.

 

[kh54s10]

Don't worry about it.
Unless you are brewing for competition etc.... why worry? Just enjoy the process.
In the end, if two people brewed the exact same beer... one had 5.2 gallons, one had 4.8... the only way you could tell the difference is with instrumentation.

But the second one produced a couple fewer bottles of beer!!!!

 

[Kharnynb]

best way is to test with water, put x amount in, boil for hour, cool and check how much is left.

then just use brewing software to plug it all in and get the numbers you need.
https://www.brewersfriend.com/windows/ is a free software that works well for me at least.