BIAB batch had low efficiency this time

[zacster]

My first two BIAB batches both had high efficiency, greater than 80%, the one I did yesterday with my friend came in low at 60% (or less). There were two issues that caused this.

First, when I bought the ingredients the first two times I specified an extra fine grind at the LHBS. It didn't look that fine, but when my friend bought his he didn't know to ask for that and it was definitely coarser.

Second, I use a 10 gallon Blichmann, and that's been fine for what I've made so far. His recipe though called for 15lbs of grain. It all fit well enough, but the bag I used probably wasn't large enough so not all the grain sat in water through the mash. I made sure to stir it all in and get it all wet but that wasn't enough to keep it submerged. I think a larger bag would work. Mine was a 5 gallon paint bag. We thought about closing the bag up and letting it sit fully in the pot instead of hanging from the rim, but there was too much grain.

We tried to "sparge" by pouring the wort over the bag after we pulled it out, but I didn't have another large enough pot to drain it in. 15lbs of wet grain is pretty large.

FG though was still a respectable 1.064 post-boil, so far from a total loss, and I'm sure it'll be a great tasting beer, 6 or 7% abv vs. 9%.

 

[Chris7687]

Hey zcaster,
Being a biab'er with only 3 AG BIAB's under my belt, I'd have to say your problem lays in the bag. I am have a few problems myself getting adjusted to AG, BIAB AG to be specific. One thing that I think is definitely a necessity is a full kettle size bag. I have the 11 gallon Bayou Classic kettle with the fryer insert and I think those extra inches of water not coming in direct contact with the grain (and in your case the grains not coming in direct contact with the mash water) is causing me low efficiencies, off flavors (tannins when trying to mash out), and difficultly on accuracy of mashing temps. I'm building a custom bag this weekend (with the help of mom who is coming to town and doesn't know why I asked her to bring her sewing machine) to fit both the kettle and the insert. I am going to experiment on efficiencies this weekend per basket size and amount of water to grain ratio. How much water did you have in your kettle? You mash out or just sparge?

 

[cyclonite]

The grain not being immersed through the mash would definitely explain the low efficiency.

+1 to the previous post on a custom bag. This should be your first priority after deciding to stay with BIAB, it really makes a difference. If you don't want to make it yourself, there are a couple of people here on the forums that make great custom bags for a great price.

Crush is also huge for efficiency, so a mill is a good idea also.

FWIW, I used to do BIAB in an 8 gallon turkey fryer, and did a dunk sparge combined with mashout in another pot. This gave me my best efficiency (90-96%). I then switched to a 15 gallon pot (boils were prone to boiling over in the smaller pot, so I had to constantly monitor), and eliminated the sparge. I've done about 25 batches this way and get 83-88% consistently (smaller beer, better efficiency and vice versa). This is all with a barley crusher mill set at 0.026 (I think, been a while since I set it), mashout, and squeezing/pressing the bag after mashout.

 

[wilserbrewer]

Problem IMO is as you suspect, marginal crush and small bag.

 

[tektonjp]

Out of curiosity, what were the OGs of your first two beers and what was your intended OG on this one? I find that 1060 is the high point for efficiency with BIAB. That is, shooting for bigger beers means less efficiency, and disproportionate addition of grains to compensate. It's not that they can't be cone, just more difficult to base efficiencies. That, plus a need to boil more off to fit a thicker OG.

 

[zacster]

The first two were in the 1.050 range, and this was supposed to be 1.078 post boil.

Next time I want to do a big brew I'll make a bigger bag, and a strainer insert is also in the works. The situation here is that I offered to do this with my friend, and it happened quickly that he was here making it. It would be another month if we hadn't done it this past weekend. As soon as I saw 15 lbs of grain I knew we'd have a problem. OTOH, I read a lot of posts on the equipment forum on how the 10 gallon pot won't be big enough to do a high gravity beer this way. That just isn't the case, there was still plenty of room in the pot and only the bag was too small.

It is happily bubbling away in any case.

 

[Chris7687]

I think they're saying a 10 g pot wont be big enough for a high gravity beer as for the same with a 5 gallon mash tun won't be big enough for a high gravity beer. There isn't enough room for the liquid and grain to fit in the kettle for say a 8-9% beer. I am personally looking at a keggle to do BIG beers and also for two batch boils. Having a 15.5g kettle would be nice to work with.

 

[wolfman_48442]

Yeah, in my experience, BIAB efficiency is probably inversely logarithmic to gravity, or some similar negative curve.
I.e. - 5 gal of 1.050 I could get 75-80% efficiency; if I was able to convince the guy at the LHBS that yes, I do want that fine a crush and no, I don't need rice hulls.
Same scenario, but 1.075 gravity - we're looking at 55% efficiency.
That's the problem. Sure, you can do a barleywine, but you're going to need a 100 gallon pot to get all the grain in there for your 20% efficiency. (I exaggerate slightly )

 

[zacster]

I think they're saying a 10 g pot wont be big enough for a high gravity beer as for the same with a 5 gallon mash tun won't be big enough for a high gravity beer. There isn't enough room for the liquid and grain to fit in the kettle for say a 8-9% beer. I am personally looking at a keggle to do BIG beers and also for two batch boils. Having a 15.5g kettle would be nice to work with.

But that's what I'm saying, it IS big enough for 15 lbs of grain, with at least another 2 gallons on top, so you could squeeze some more in there. You don't need to boil that amount, just mash, so there is no worry about boil over with it that close. The bag I used only went down about half way, and not as wide as the pot.

 

[stux]

Yeah, in my experience, BIAB efficiency is probably inversely logarithmic to gravity, or some similar negative curve.
I.e. - 5 gal of 1.050 I could get 75-80% efficiency; if I was able to convince the guy at the LHBS that yes, I do want that fine a crush and no, I don't need rice hulls.
Same scenario, but 1.075 gravity - we're looking at 55% efficiency.
That's the problem. Sure, you can do a barleywine, but you're going to need a 100 gallon pot to get all the grain in there for your 20% efficiency. (I exaggerate slightly )

I actually worked this out. It turns our Pure BIAB (ie no sparge), the efficiency is related to the liquor:grain ratio. The higher the ratio the higher the efficiency. Thus you want as much water in your mash as possible.

The loss from the mash, ie the difference between your Efficiency Into Kettle and 100% is pretty close to the ratio of a Real Absorption vs Total Mash Liquor

My results and a calculator which can accurately predict your OG 1.100 barley wine biab are here : http://www.biabrewer.info/viewtopic.php?f=74&t=1066