First BIAB - really low efficiency - tips for next time?

[czeknere]

Took a few years off brewing as other life events got in the way, but I'm now getting back into it all. Previously, I used a cooler mash tun and went full all grain - this time around I wanted to simplify a bit and went BIAB. Grabbed a new 19 gallon kettle and a 15 gal FermZilla.

First batch was last weekend and I definitely had some rust to shake off. Recipe:

Milkshake IPA - 11 gal BIAB

16# Pale
3# Wheat
2# Flaked oats
1# Honey
1# Lactose - 15 min
--
1.5 oz warrior 60 min
3oz citra, 3oz mosaic, 1.5oz galaxy - flameout.
--
Vermont IPA yeast

12.5 Gal water for mash, held at 152 for 60 min
3 gal reserved for dunk sparge, heated to 175.

Pre-boil gravity was 1.026, post-boil was 1.040. Calculated efficiency was 46%.

I'm not quite sure how I missed the efficiency target so much. Expected pre-boil was 1.046 according to the recipe, and 1.056 SG. My only thought is that I could have increased the grain bill a bit to compensate, but the recipe was specifically designed for BIAB so I wasn't expecting to need to.

Any tips for next time around?

 

[beernutz]

How fine did you crush your grain and how long did you mash? Were any water additions or pH corrections used?

 

[czeknere]

- Grain was crushed from the supplier, it looked like it usually did when I brewed normal all grain.
- 60 min mash.
- No water corrections, used filtered water.

I had read about double crushing for BIAB, I should have asked for that!

 

[LittleRiver]

It's almost certain the problem is with your grain crush.

If you plan to stick with BIAB, make getting your own mill a priority. In addition to a huge boost to your efficiency, you can buy base grains in bulk and save a considerable amount of money. The mill will pay for itself.

I consistently get brewhouse efficiency in the low 80's with a mill gap of .025", no re-circulation, no sparge, and no squeezing of the bag (it drains over the kettle for the entire boil).

 

[beernutz]

I have a fixed gap mill so I double crush, mash 90 minutes, use water and pH additions, and pretty consistently get 78-79% efficiency when I do BIAB 10 gallon batches. I also let my bag hang over the kettle during the boil but I have to squeeze the bag and sparge with about 1 gallon of water poured over the bag to get to that efficiency range.

An adjustable mill would be nice but I'm going on close to 20 years with the one I have and the extra steps to increase efficiency aren't difficult or time consuming.

 

[Yorkshire lad]

Took a few years off brewing as other life events got in the way, but I'm now getting back into it all. Previously, I used a cooler mash tun and went full all grain - this time around I wanted to simplify a bit and went BIAB. Grabbed a new 19 gallon kettle and a 15 gal FermZilla.

First batch was last weekend and I definitely had some rust to shake off. Recipe:

Milkshake IPA - 11 gal BIAB

16# Pale
3# Wheat
2# Flaked oats
1# Honey
1# Lactose - 15 min
--
1.5 oz warrior 60 min
3oz citra, 3oz mosaic, 1.5oz galaxy - flameout.
--
Vermont IPA yeast

12.5 Gal water for mash, held at 152 for 60 min
3 gal reserved for dunk sparge, heated to 175.

Pre-boil gravity was 1.026, post-boil was 1.040. Calculated efficiency was 46%.

I'm not quite sure how I missed the efficiency target so much. Expected pre-boil was 1.046 according to the recipe, and 1.056 SG. My only thought is that I could have increased the grain bill a bit to compensate, but the recipe was specifically designed for BIAB so I wasn't expecting to need to.

Any tips for next time around?

Did you do an Iodine test?

 

[Redpappy]

I consistently get brewhouse efficiency in the low 80's with a mill gap of .025", no re-circulation, no sparge, and no squeezing of the bag (it drains over the kettle for the entire boil).

Do you do a double crush? I hear some people get high efficiency, I get 70-73% efficiency, single crush cereal killer set at .025 60 min mash.

 

[LittleRiver]

Do you do a double crush?

Nope, single pass through a Kegco 3 roller mill.

 

[ChiknNutz]

As a point of reference, I did my first 5G BIAB batch on Sunday and achieved just north of 86% with no sparging, just squeezing the bag. This was with a double crush from Atlantic Brew Supply as I don't have my own mill.

 

[czeknere]

Did you do an Iodine test?

I did not.

 

[Yorkshire lad]

I did not.

If the Iodine turns black, its an indication that the mash is not fully converted

 

[Gruel]

Are you sure about the wort densities? The temperature corrections can become pretty large if you measure hot wort.
Preboil 1.026, postboil 1.04 means you boiled away 35% of your wort; 0.35 * (12.5 + 3 - 2*) = almost 5 gallon. Does that sound likely?
(*): assuming 2 gallon stuck in bag

Maybe your hydrometer developed a crack over all those years, and is reading too low?

 

[doug293cz]

If the Iodine turns black, its an indication that the mash is not fully converted

A much better test than the "iodine test" is to measure the SG of the wort in the mash. This will give you a quantitative measure of your conversion efficiency in real time. Iodine can't do that. Find the method here.

Brew on

 

[czeknere]

Are you sure about the wort densities? The temperature corrections can become pretty large if you measure hot wort.
Preboil 1.026, postboil 1.04 means you boiled away 35% of your wort; 0.35 * (12.5 + 3 - 2*) = almost 5 gallon. Does that sound likely?
(*): assuming 2 gallon stuck in bag

Maybe your hydrometer developed a crack over all those years, and is reading too low?

That's an interesting thought. I did measure pretty hot wort, but did a correction - maybe I was really off in my correction though. I will say - I did hit 13 gal pre-boil and ~9.5 gallons hit the fermenter, but there was plenty of trub. I'll take a closer look at my hydrometer, my FG was 1.008 which was right inline with what I expected.

Brewing again this weekend and I plan to incorporate some of the feedback here for sure. I'll make sure the pre-boil wort drops to a better temp when measuring.

 

[czeknere]

A much better test than the "iodine test" is to measure the SG of the wort in the mash. This will give you a quantitative measure of your conversion efficiency in real time. Iodine can't do that. Find the method here.

Brew on

I'm sorry - can you expand on this a bit? Specifically the "measure the SG of the wort in the mash". Exactly how is this done and how is it different than pulling a sample before the boil and testing that? Or does it mean measure your SG separately before and after you sparge?

 

[RM-MN]

I'm sorry - can you expand on this a bit? Specifically the "measure the SG of the wort in the mash". Exactly how is this done and how is it different than pulling a sample before the boil and testing that? Or does it mean measure your SG separately before and after you sparge?

An iodine test is a yes/no. Either you have full conversion or you don't. Taking a gravity sample is more nuanced. If you have full conversion your gravity sample will indicate that but it will also tell you if you have only 75% conversion in which case you can add time to the mash to get closer to full conversion. This is best done with a temperature compensated refractometer and before you sample be sure to stir the mash thoroughly as the sugary wort wants to settle and taking a sample from the top will show you having poorer conversion.

 

[doug293cz]

I'm sorry - can you expand on this a bit? Specifically the "measure the SG of the wort in the mash". Exactly how is this done and how is it different than pulling a sample before the boil and testing that? Or does it mean measure your SG separately before and after you sparge?

You stir the mash and take a sample of the wort directly from the mash tun. This is done before lautering or sparging to allow you to continue the mash if your conversion is not complete. As said above, a refractometer is the best instrument for doing this sample.

For any given mash thickness (water to grain ratio) and grain bill potential, there is a maximum wort SG that can be calculated, and this SG will be obtained when you have 100% conversion. If you measure the wort in your mash and the SG is less than the calculated max, then your mash conversion is less than 100%. It turns out that most typical grain bills have a potential close to 1.037 (or 37 ppg), and the max SG vs. mash thickness has been tabulated at the link I provided in my previous post.

Brew on

 

[odie]

mill your grain fine. I run mine thru 2-3 times

 

[Gruel]

It turns out that most typical grain bills have a potential close to 1.037 (or 37 ppg), and the max SG vs. mash thickness has been tabulated at the link I provided in my previous post.

Brew on

All good advice, except for that last '1.037' out of the blue. That's like saying most cars have 150 horsepower. And what is ppg; parts per gazillion?

 

[doug293cz]

All good advice, except for that last '1.037' out of the blue. That's like saying most cars have 150 horsepower. And what is ppg; parts per gazillion?

Most base grains have about 80% of their dry weight that can be converted to sugar, dextrins, soluble starch, soluble proteins, lipids, and a few other minor components. It turns out that this amount of soluble material will create a wort with an SG of about 1.037 if you mash 1 lb of grain in enough water to make 1 gal total of wort (note that this is less than 1 gal of water as the sugar, etc. also contributes to the volume of wort.) "ppg" stands for "points per pound per gallon", and the base grain above is said to have an potential of 37 points per lb, and the resulting 1 gal of wort would contain 37 points per gallon. We really should be talking about grain as points per pound, and wort as points per gallon, but the usage of ppg is too ingrained to ever get the brewing community to use "proper" units.

Since most grain bills are 80% or more base grains, and even the non-base grains contribute more than 20 points per lb, you won't make a huge error by simply assuming that the total grain bill has a potential 1.037 or 37 ppg. If you want to be really accurate, you should multiply the weight of each grain in the grain bill by its ppg, add them all up, and divide by the total grain weight. This is the "weighted grain potential" for the particular grain bill.

Also, if you want to be really accurate, you must correct for the moisture content of the grains used - usually about 4%. This means that if the dry potential is 80% or 1.037, the "as is" potential is 0.96 * 80% = 77% or (35.5 ppg / 1.0355.)

To get really accurate grain potentials or moisture contents you need to get a malt analysis sheet for the specific lot of grain you are using. Unfortunately, these are hard to come by for homebrewers. Most brewing software contains a database of "typical" potentials for different types of grain. How well these match the grain you have is anybody's guess, but they should be within a few percent.

With all of the potential sources of error (grain weights, grain potentials, volume measurements, moisture content, SG measurements) often it is just easier to use an approximate weighted grain potential to get you an estimate of the maximum obtainable wort density for the particular mash thickness. If doing this, 1.037/37 ppg is a pretty good number to use.

Brew on

 

[bwible]

Everybody goes straight to crush. First thing I would make sure is to properly stir the mash thoroughly and make sure you break up any dough balls and there are no dry pockets. Dough balls and dry pockets are the #1 efficiency killer. Grain that doesn’t get wet won’t give you any sugar. For some reason this is more common with BIAB. People don’t stir as thoroughly with the bag as they would in a mash tun. Its not just putting a grain in a bag and dunking like a tea bag. You still have to stir. Basic, I know.

or yes, hydrometer correction for temp

 

[bracconiere]

Pre-boil gravity was 1.026, post-boil was 1.040. Calculated efficiency was 46%.

that seems like a lot for just boiling off 3 gallons? sure you're measuring everything right? i punched in a 11 gallon batch into beersmith, for a 1.026 pre-boil, and after boiling down only would end up with 1.018.....did you take your pre-boil with temp correction? 1.026 is around what i get when i drop the hydro in the pot before the boil....at sparge runoff temp ~130f...

 

[Fewk]

As a point of reference, I did my first 5G BIAB batch on Sunday and achieved just north of 86% with no sparging, just squeezing the bag. This was with a double crush from Atlantic Brew Supply as I don't have my own mill.

I also double-crush at Atlantic.

 

[chrisz]

I'm new here so this double crushing thing is news to me, is there any downside to that? My first BIAB batch came in way too thin also, but then I came up with a sparging technique and I'm plenty efficient, as far as I can tell even a makeshift sparge has made all the difference

 

[LittleRiver]

I'm new here so this double crushing thing is news to me, is there any downside to that? My first BIAB batch came in way too thin also, but then I came up with a sparging technique and I'm plenty efficient, as far as I can tell even a makeshift sparge has made all the difference

If you're the one doing the crushing, the downside is that you have to do that work twice. Other than that, there's no real downside to it.

Generally speaking, double crush is technique to get a little finer milling of grains on a mill that is setup for a coarser crush (which is typical for traditional non-BIAB brewing rigs).

If you have your own mill, just set the roller gap for a fine crush (~.025") and crush it once -- no need to double crush. With a fine crush you may find that you don't need to sparge to get great efficiency. I typically don't sparge, and only do so if I'm shooting for an OG above 1.065.