help using BIAB calculator for first time

[fun4stuff]

I am going to do my first BIAB today. I wanted to make sure I am understanding the calculator correctly first. I've been using a number of the websites and have been getting different answers.

Here is basic info: 5 gallon batch, mash temperature 158 degrees, 90 minute boil, 19 gallon pot, 1.25 gallons/hr boil off, 0.25 gallons trub, 0.125 grain absorption, 0.0365 hops absorption, 71 degree grain temp.

So using the excel document on this website:
http://biabbrewing.com/brew-day-prep/biab-calculators-and-software/

This is Your Strike/Mash Water Needed: 8.8 gallons

Bring Your Strike/Mash Water To This Temperature: 164.4 ⁰F

So, I will start out by heating 8.8 gallons of water to 164.4 and then add the grains, correct?

 

[Foosier]

that seems right for a pot that big and a batch that size.

 

[browder]

I use Priceless calculator simple to use-----

 

[pricelessbrewing]

Use mine, it was original based on that one but I added quite a few things and cleaned it up so it's easy to use.

Couple of things on your variables.
Trub loss is usually about 9% or so of your volume into the fermenter.
BIAB absorption is usually around 0.08, 0.125 is for traditional mash tuns where the grains aren't moved or squeezed.
1.25 gal/hr seems a little low for that size of a pot.
To give accurate answers, we need to know the grain bill and hop bill.

Yes, the strike volume and temp is the water you add the grains to. I usually aim a degree or two above it, so that after doughing in (adding and stirring the grains thoroughly) I can stir a bit more to bring the temp down a bit and let it mix well.

Stirring is important.

Also, hello fellow Michiganders!

 

[casualbrewer]

I just my first BIAB as well and calculated 8.5 gallons of water needed for 9.5 lbs of grain to end up with 5.5 gallons. I ended up with closer to 6.5 gallons. I did squeeze the bag a good bit to get all the sugary wort out I could. Either the grain didn't soak up as much as I expected or my boil off rate wasn't that bad. If my boil off rate was 1.25 gallons for the hour boil then my grain only soaked up .07895 gallons per pound of grain. If I only boiled off a gallon then my grains soaked up .105 gallons per pound.

 

[pricelessbrewing]

I just my first BIAB as well and calculated 8.5 gallons of water needed for 9.5 lbs of grain to end up with 5.5 gallons. I ended up with closer to 6.5 gallons. I did squeeze the bag a good bit to get all the sugary wort out I could. Either the grain didn't soak up as much as I expected or my boil off rate wasn't that bad. If my boil off rate was 1.25 gallons for the hour boil then my grain only soaked up .07895 gallons per pound of grain. If I only boiled off a gallon then my grains soaked up .105 gallons per pound.

Either sounds possible, .25gal is not a huge difference to be off on your boil rate if you haven't measured it well yet. Make sure you measure the pre boil and post boil volume, I use a metal ruler to determine the height of the wort which gives me the volume.

0.105 is a possible absorption if you don't squeeze or let it drain all the way. I put the grain in a perforated bucket, then press down with a pot lid. Letting the grain sit in the bucket over night ends up draining about a cup more, so I'm satisfied with this method.

 

[casualbrewer]

Yeah I squeezed mine like it owed me money lol.

 

[eadavis80]

I've been told you want to mash around 152, not 158. I think I mashed around 158 last time and my efficiency was horribly low. Others posted and have said a 158 mash is fine, so I'm just giving you my experience. When doing a 3-gallon BIAB I started with 5.5 gallons of water and after a 60-minute mash and 60-minute boil with 7.625 pounds of grain and 3 ounces of hops, I was at 4.25 gallons of wort and it was much lower gravity than the target. So, you can either end with higher than your target pre-boil volume and then boil off until you get your desired pre-boil volume, or you can undershoot your pre-boil volume and then sparge to make it up. As you can tell, I'm still learning the process, but I'm anxious to try again Thursday!

 

[Onkel_Udo]

I've been told you want to mash around 152, not 158. I think I mashed around 158 last time and my efficiency was horribly low. Others posted and have said a 158 mash is fine, so I'm just giving you my experience.

Withing reason, the temp of your mash does not effect the efficiency, just the fermentability. Give or take 148-158 f will return about the same OG but the difference in FG will be noticeable.

 

[eadavis80]

Then can you advise me how much water you'd suggest starting with for a 3-gallon BIAB 7.625 pound grain bill with 3 ounces of hops?

 

[casualbrewer]

I'm coming up with 4.86 gallons. That is assuming .08 gallons absorbed per lb of grain and a 1.25 boil off rate for 1 hour boil. I would start at 5 gallons to be safe. Can always boil a bit longer to hit desired level if needed. Remember that is if you do a good squeezing.

 

[Cider123]

OP, I am assuming you are using the BIABacus. This is what I use and I like it very much. It is confusing at first, but spending some time and asking questions over at their site has made it very easy.

You dont need to fill in every section unless you want to know all the efficiency calculations. I do enough to figure the amount of grains, water, hops and boil time to get the final volume, OG and IBU's I want. With this spreadsheet I hit my OG practically every time and I now trust it completely.

 

[pricelessbrewing]

I've said this a lot. While the BIABacus is a great piece of software, it's a bit overkill for most situations. The place that I've seen it excel the most, is when scaling recipes. However the "necessary" info, VAW, for it to do it accurately is missing 95% of the time from a recipe so imo it's basically the same as just doing a linear adjustment. 3 gallons? Do 3.3/5.5 of all ingredients and hops.

Remember that if you want 3 gallons out of the fermenter, you need to aim slightly above it to account for trub. In my experience, it's about 9-10%. Aim for 3.3 gallons into fermenter.
My calculator is coming up with 5.27 gallons.

http://pricelessbrewing.github.io/BiabCalc/

 

[hopkincr]

I use simplebiabcalculator.com.

 

[pricelessbrewing]

I use simplebiabcalculator.com.

check out mine instead. It had quite a few more features simple does not, while still being easy to use. At the time it was realized he did a great job but there's quite a few variables that are locked in that keep it from being more versatile and accurate.

 

[jaydlaw]

check out mine instead. It had quite a few more features simple does not, while still being easy to use. At the time it was realized he did a great job but there's quite a few variables that are locked in that keep it from being more versatile and accurate.

I like it! It is very easy to understand, and has preset variables (u can change if needed). this needs to be an app!

 

[Mofoa]

Been a couple of years since I last BIAB'd...and have used my cooler for my last several batches.

Glad to have found this thread as I wanted to do another BIAB this weekend, and the priceless calculator is precisely what I was looking for.

I wanted to know how to calculate my strike water/temps. Easy peasy.

 

[pricelessbrewing]

I like it! It is very easy to understand, and has preset variables (u can change if needed). this needs to be an app!

Working on it :rockin:

 

[william_shakes_beer]

Remember also, boil off is a function of the diameter of your boil kettle. A 14" diameter kettle (for instance) will boil off 1 gallon per hour given same boil vigor, whether its a 5 gallon batch, 10 gallon or 20. Some calculators mistakenly use a percentage of the batch. That's not how it works.

 

[pricelessbrewing]

Remember also, boil off is a function of the diameter of your boil kettle. A 14" diameter kettle (for instance) will boil off 1 gallon per hour given same boil vigor, whether its a 5 gallon batch, 10 gallon or 20. Some calculators mistakenly use a percentage of the batch. That's not how it works.

Agreed. Many of the older recipes and calculators used % boil off, which is not accurate at all.

Boil off is affected by humidity, and ambient temperature of the environment as well, but mostly the diameter of the kettle.

 

[hezagenius]

@pricelessbrewing

What is the assumed coefficient for the volume of 1 lb of dry grain? I was using the strike water volume, grain bill and absorption coefficient and backed out a volume of ~0.087gal per lb of dry grain, or about 11.5 lbs of dry grain per gallon of grain. Is that similar to the number you are using?

 

[pricelessbrewing]

The mash volume formula I use is

VolMash = (VolStart + GBill * 0.08) * MashAdj
MashAdj is the thermal expansion at mash temps, and is usually around 2% expansion so 1.02~.
I should probably change it to
VolMash = (VolStart * MashAdj) + GBill * 0.08

But The difference is tiny (0.02 gallons for a 12 lb grain bill), and i would rather leave some overestimate slightly so you can stir in the mash a bit.

 

[hezagenius]

What about the actual volume of the grain?

I have a grain bill of 12.75lb and I am using an absorption coefficient of 0.08gal/lb. The temp adj strike water volume is estimated at 9.76gal and the total mash volume is estimated at 10.80gal.

Wouldn't the total mash volume = strike water volume + dry grain volume - (0.08*dry grain volume)?

 

[pricelessbrewing]

The grains displace 0.08 during the mash and absorb 0.08 after the mash.

mash volume is strike + grains * 0.08
Preboilwill be strike - volume absorbed by grains (grains * 0.08)

 

[pricelessbrewing]

Sorry for the double post, just wanted to make sure it was clear as I was on my phone at work earlier.

You wouldn't subtract the volume absorbed by the grain, as it's there both before and during the mash. It doesn't leave the mash volume until the grains and sweet liquor are separated at the end of the mash.