BIAB -- What Happened??!

[Apulver]

Hello all,

I just finished my first AG batch using the no-sparge BIAB method. I followed this recipe exactly, though I double-milled the grain at my local homebrew store:

https://www.homebrewtalk.com/f71/austin-homebrews-blue-moon-clone-ag-30190/

So calculating the recipe out on Beersmith (v1), I started with 7.65 gallons of water for my mash. The goal was to hit 1.046 OG with a batch size of 5.5 gallons.

Before I pitched yeast, my OG was 1.044 with a volume of only 4.25 gallons!!!

I didn't let the grain bag drain much... but I squeezed the hell out of it! Am I missing something here? I can't imagine how low my OG would have been if I had added water to reach my target batch size.

Help!

 

[KavDaven]

How positive are that you hit, shorted or over shot your temps?

How long did it take between temp steps? Perhaps, you lost too much to evaporation?

 

[TopherM]

The starting volume seems to be in range. I do 5.0 gallon batches, and typically start with around 7.0-7.2 gallons.

The 1.044 off of 1.046 isn't that big of a deal, pretty much spot on, but the 4.25 gallons certainly is an issue.

Did you do a 90 minute boil by chance, due to the Pilsner malt? If your pot has a higher boil off rate than the original recipe, and/or you did a 90 minute boil while the original recipe did a 60 minute boil, then that could be it right there.

Pretty much the only places you could have lost that much volume is boil off or not getting a large % of the wort out of the grain when squeezing/draining. I typically only lose about 0.4-0.6 gallons to absorbtion, but I press the crap out of my BIAB bag.

You could have also literally started with less volume than you thought. I fill my starting volume with a one gallon pitcher, and more than once I've lost count!

Just some ideas....you really couldn't have lost over 3 gallons without it being one of the above, and it certainly couldn't have JUST been grain absorbtion.

 

[rhamilton]

My first BIAB was real tough -- hit 40% eff :-/

#1. Get iodine and do the iodine test. You might have left starched unconverted, iodine will tell you when it's done. How long did you mash?

#2. +1 for KavDaven -- accurate temps is critical for BIAB. It's also hard to get a good reading from the middle of the bag.

#3. Stir stir stir stir. I stir every 20 minutes until the iodine test passes. It's also important during the beginning of the mash to get reliable temperature distribution. The liquid outside the bag may be right, but I've seen instances where the middle of the bag is a good 20°F lower than the target due to lack of stirring. Add heat after stirring to maintain target temps for the duration of the mash.


The above corrections took me from that pathetic 40% to a consistent 75%.

As for missing your target volume, do you know your boil-off rate and do you boil at the same heat every time?

Another little tip: after you are done dripping and squeezing the bag, do a 1 gallon sparge (cold or hot, no difference) and you'll get a little more out of the grains.

 

[tre9er]

Your volume being low pretty much has to be due to not adding enough water to begin-with (from losing count or messing up math) or due to increased evap. rate and/or longer boil.

I lose 0.19g/lb. of grain to absorption, boil off just over 1g/hr, and have dead space in the tun and kettle to account for.

 

[Apulver]

Thanks for the tips on efficiency.

As far as hitting temps, I hit the protein rest spot-on, though the temp dropped about 2-3 degrees by the end of the 30 minute step. I was a little high on the saccrification, but no more than 4 degrees (again, with temps dropping to my target before the end of the 30 minute step). And I nailed the mash out temp. Sounds like stirring could be a big issue... I stirred a ton while heating but mostly left the mash untouched once I hit a target temp.

The water loss is still a bit of a mystery though...

I think the time in between temp steps during mash was somewhere around 10 minutes each. It was only a 45 minute boil (which is even more concerning), with 10 minutes of boil time post-mash before adding my first hops. As far as being short on the amount of water up-front... I used bottled one-gallon bottles and emptied them all (except for the 8th, to reach 7.65).

My boil-off has never been too bad... maybe around a gallon per hour?

 

[pvtschultz]

Also, quadruple check the crush gap at your LHBS. I have a Northern Brewer in my neighborhood and one of their two rollers is set to 0.045" (so they say). Even with a double crush, I only got 60%-65% overall efficiency. I now use a Corona type mill and get a repeatable 75% efficiency using the exact same process.

 

[tre9er]

Ohhhhh, this recipe calls for flaked grains, yeah? That stuff absorbs more water than you imagine. I've come up short using flaked wheat and oats almost every time. That's where I'm thinking this could have happened.

 

[pvtschultz]

My boil-off has never been too bad... maybe around a gallon per hour?

Well, by my math you lost a bunch to the fairies then...

Start with ~7.5 gallons (easy math), lose 0.5 gallons to absorption, lose another gallon to boil-off, and lose another 0.5 gallons to misc losses and you come to 5.5 gallons. You can always top off at the end of the boil to get your starting gravity and volume inline, that's not a huge issue though you do have a slight contamination risk. Your efficiency was quite low though, but perhaps not. My refractometer is only accurate when the wort is at or very near room temperature even though it has ATC capabilities. I've found that it will read a full brix low when the wort is warm even after sitting on the lens for 15-20 seconds.

 

[Apulver]

Hmmmmm.... Well, looking at the math, things are starting to become a little clearer now. Sounds like it's a combination of a number of things.

(1) Losing 1 gallon per hour or so means that with an hour(+?) mash and 55 minute boil (considering the 10 minute post-mash boil), I'm going to probably lose around 1.25 to 1.5 gallons. That would take me from a target 5.5 gallons to a yield of 5.00-5.25 gallons.

(2) Add to it the increased absorption of 4 pounds of flaked wheat/oats, and I'm probably in the 4.75 to 5.00 gallon range (?)

(3) Add to it the fact that this is my first AG and BIAB and I probably didn't squeeze the bag hard enough, etc, etc... maybe not such a mystery after all

Well maybe a quick 1-gallon sparge after mash-out could kill two birds with one stone... help with efficiency AND renew my boil volume.

Thanks for all the suggestions... please keep them coming! I want to get this right next time!

 

[weirdboy]

Regardless of what the recipe says, you really ought to plan for a 90 minute boil with that much pilsner malt.

Also, how sure are you on all the measurements? How about your assumption of 1 gallon per hour? Have you tested this pot before to know the boil-off rate accurately?

Do you have any losses to dead space in your boil kettle, tubing, or to trub? I know I lose somewhere between .25-.5 gallons each brew to this kind of thing on my BIAB system, so that is always factored into my recipes when I brew.

If you don't have one, get a refractometer, and start taking both volume and gravity readings after you "mash out" of your BIAB system and you start getting to a boil, and then take another reading after about 30 minutes. See if you are on target to hit your planned OG given your boil-off rate, and make adjustments as necessary if you are not.

 

[Apulver]

Yes, the one-gallon boil off estimate is based upon the 2-3 extract full boils I've done with the same pot.

As far as measuring volume during the boil, is there an easy way to do this without a site glass? I'm assuming that marking the inside of the kettle isn't an option...

 

[pvtschultz]

As far as measuring volume during the boil, is there an easy way to do this without a site glass? I'm assuming that marking the inside of the kettle isn't an option...

You can calibrate a wood dowel, a length of CPVC tubing, or even your mash paddle by adding 1 gallon to the pot and marking the level on the stick. The water volume will increase by about 0.05 gallons/gallon at boil temperatures over room temperature (I'm going from memory here but BeerSmith can do the adjustments as well.

 

[stux]

With a reduced final volume and still a lower OG than you were expecting it indicates an efficiency problem.

I would suggest

1) possibly a finer grind
2) 90 min mash
3) agitate the mash with a potato masher every 20 minutes. You can use this time to check the temperature, and possibly apply some more heat
4) 90 min boil

You shouldn't have to squeeze the bajeezus out of your bag, it should pretty much drain completely if you hang it above your kettle while you're coming to the boil.

 

[wherestheyeast]

Have you checked out biabrewer.info ?

I did my first ag batch biab last week after one of the senior members there customized a spreadsheet for my recipe & equipment. My actual numbers (volumes, gravity, etc.) were almost exactly what was estimated in the provided spreadsheet & my efficiency was ~75%. I double milled the grain at LHBS, squeezed the crap out of the bag but didn't perform additional sparging.

 

[Apulver]

So I figured I'd follow-up with a little information after my second BIAB.

Brewed a Kolsch yesterday. My target final volume was 5.71 gallons with a an OG of 1.053. I hit the volume (I think... see #4 below) and ended with a OG of 1.052.

Here's some changes I made and things I noticed:

(1) Started with 8 gallons of water for the mash. Kept the lid on as much as possible (except for when boiling) to minimize loss.

(2) I squeezed the bag like a mad man... oh how I squeezed that sucker... and then dunked it back into my wort and squeezed some more.

(3) Added 1 cup of light DME out of paranoia that my OG would be too low even after boiling off some liquid

(4) A problem! I use both a false bottom and (underneath it) a bazooka screen to filter out hops and hot/cold break. I noticed that when it appeared all of the wort had been drained out of the kettle, there was still a sizable amount of liquid in the kettle. Something was keeping it from draining. I moved the kettle around a little and was able to get some more wort out, but ultimately still left a lot of liquid inside. I hit my goal of 5.5 gallons in the fermenter, but probably would have had a better OG/efficiency had I boiled off the proper amount of water and drained everything out of the kettle.

My bazooka screen was totally caked with hot/cold break, which surprised me considering I have the false bottom. This is a problem I'll have to figure out... BUT -- probably explains why I had such a low yield during my first BIAB. I bet I left a decent amount of liquid in the kettle while thinking that it was drained (since the flow stopped entirely)

In any case, cheers to all of you for your help! Thanks!