Different efficiencies between batches of low alcohol and high alcohol ... Why?

[Miles_1111]

I have recently started with BIAB and have brewed 4 batches, two low alcohol ( 2 pale ales of 6% and 5.3%) and two high alcohol ( wee heavy 8.6% and barleywine 10.3%). However, I notcied my mash efficiency is different between them. For two low alcohol batches it is around 77%, but for two high alcohol batches is about 67%. I did not change the gap between the grind and used the same method, using Beersmith to calculate the water-to-grist ratio and mashing temperature. Is this difference normal? If yes, I should change the mash efficiency in the profile before each brew in the future? Thank you. Cheers.

 

[VikeMan]

Yes, this is normal. Your observation makes it sound like a binary thing, but it's really a continuous function.

Recipes with larger grain bills (but the same pre-boil volume) require more total water, because of more grain wort absorption. So the ratio of absorbed wort to total wort (including absorbed) is larger. Therefore a smaller percentage of the total sugars/dextrins produced makes it to the kettle.

 

[JohnnyO']

Recipes with larger grain bills (but the same pre-boil volume) require more total water, because of more grain wort absorption. So the ratio of absorbed wort to total wort (including absorbed) is larger. Therefore a smaller percentage of the total sugars/dextrins produced makes it to the kettle.

With my system - i calculate my strike volume based on the total grain bill. My last brew was my biggest grain bill ever (still not huge) but my mash efficiency was also my highest to date - at 84ish IIRC. I had been running in the 78 range for lower ABV brew.

 

[VikeMan]

With my system - i calculate my strike volume based on the total grain bill. My last brew was my biggest grain bill ever (still not huge) but my mash efficiency was also my highest to date - at 84ish IIRC. I had been running in the 78 range for lower ABV brew.

Sure, you can further increase the water and maintain/increase mash efficiency, but then you do need a longer boil to get down to the same batch size.

 

[LittleRiver]

The only time I sparge is when my target OG is over ~1.065. The sparge helps offset the reduced efficiency that comes with a big grain bill. I find this to be the easiest way to do a BIAB sparge:

• mash with 50% of the total water
• drain the wort into a bucket, leaving the bag and grains in place
• add the remainder of the water to the grains, stir thoroughly
• raise the bag, fire the heat for the boil, pour the bucket of wort into the kettle

Let the bag drain over the kettle during the entire boil, there will be no need to squeeze it.

 

[JohnnyO']

Sure, you can further increase the water and maintain/increase mash efficiency, but then you do need a longer boil to get down to the same batch size.

The formula works to provide the correct volume to produce either a 5 gallon or 6 gallon batch for any size grain bill (up to capacity) - for a 60 minute boil.

Screenshot 2020-12-02 110102 by John O'Neil, on Flickr

 

[VikeMan]

^ Ok, your BIAB formula, for example, is accounting for grain absorption, plus batch size, plus boil off.

With that (pretty standard) approach, larger grain bills will result in lower mash efficiency, assuming no other process changes. If you see the opposite, there is something else going on that you are not accounting for or measuring. For example, your final volume might be off (very common cause of mis-calculated mash efficiencies) due to inaccuracies in assumptions (such as absorption losses or boil off rate). Or the grains used may have actually had higher potential PPG contributions than assumed. etc.

http://sonsofalchemy.org/wp-content/uploads/2020/04/Mash_Efficiency_and_Brewhouse_Efficiency.pdf

 

[JohnnyO']

^ Ok, your BIAB formula, for example, is accounting for grain absorption, plus batch size, plus boil off.

With that (pretty standard) approach, larger grain bills will result in lower mash efficiency, assuming no other process changes. If you see the opposite, there is something else going on that you are not accounting for or measuring. For example, your final volume might be off (very common cause of mis-calculated mash efficiencies) due to inaccuracies in assumptions (such as absorption losses or boil off rate). Or the grains used may have actually had higher potential PPG contributions than assumed. etc.

http://sonsofalchemy.org/wp-content/uploads/2020/04/Mash_Efficiency_and_Brewhouse_Efficiency.pdf

I record pre-boil volume (at mash temp) and pre-boil gravity (by refractometer of a cooled sample) for each batch. If I am doing it incorrectly, I am doing it consistently incorrectly. The numbers on the side of the kettle are pretty easy to read, though.

 

[VikeMan]

I record pre-boil volume (at mash temp) and pre-boil gravity (by refractometer of a cooled sample) for each batch. If I am doing it incorrectly, I am doing it consistently incorrectly. The numbers on the side of the kettle are pretty easy to read, though.

That's good. Now, take the same grain bill (exact same grains, even the same maltster(s)) as you used in your big beer, but shrink it (to some % less than 100), and make a wort with the same pre-boil volume. Your mash efficiency will be higher with the smaller grain bill, assuming you really use the same grain types, get the same pre-boil wort volume, and haven't changed any other part of the process.

 

[JohnnyO']

That's good. Now, take the same grain bill (exact same grains, even the same maltster(s)) as you used in your big beer, but shrink it (to some % less than 100), and make a wort with the same pre-boil volume. Your mash efficiency will be higher with the smaller grain bill, assuming you really use the same grain types, get the same pre-boil wort volume, and haven't changed any other part of the process.

Yeah - that's not what either the OP or I am talking about. Seems as though we may be on two different topics.

 

[VikeMan]

Yeah - that's not what either the OP or I am talking about. Seems as though we may be on two different topics.

I'm saying that bigger grain bills, for the same batch size (pre-boil) with the same grain types (or at least accurate PPG estimates if the grain types are different), and no changes to process, will yield lower mash efficiency. This is the explanation for the OP's observation.

What are you saying?

 

[JohnnyO']

The OP said that for bigger and different grain bills he observed lower mash efficiency than for brews with smaller different grain bills. And I said that I have observed the opposite.

If the OP had said what you are saying - I would not have chimed in at all - as I have no experience in doing what you proposed that I do. And I can't for the life of me figure out why I would do that.

 

[VikeMan]

The OP said that for bigger and different grain bills he observed lower mash efficiency than for brews with smaller different grain bills. And I said that I have observed the opposite.

The OP's observation is correct, and clearly driven by the science of mash volumes and concentrations. I will say this one last time, and then leave it: If you observe the opposite, there's something wrong with the measurements and/or assumptions about the potential extract from the particular grains in one batch or the other. Or something else in the process was changed.

 

[JohnnyO']

The OP's observation is correct, and clearly driven by the science of mash volumes and concentrations.

The science of the thing that he did not do?

 

[Miles_1111]

Yes, this is normal. Your observation makes it sound like a binary thing, but it's really a continuous function.

Recipes with larger grain bills (but the same pre-boil volume) require more total water, because of more grain wort absorption. So the ratio of absorbed wort to total wort (including absorbed) is larger. Therefore a smaller percentage of the total sugars/dextrins produced makes it to the kettle.

I see what you mean. This logic is based on using the same total water as the less grain bills batches for larger grain bills, right? If I increase the total water for the larger grain bills accordingly, the ratio of absorbed wort to total wort (including absorbed) should be the same, is that correct?

 

[VikeMan]

I see what you mean. This logic is based on using the same total water as the less grain bills batches for larger grain bills, right? If I increase the total water for the larger grain bills accordingly, the ratio of absorbed wort to total wort (including absorbed) should be the same, is that correct?

No, it's based on having the same amount of wort run off from the mash. There will be more total water for the larger grain bill to get that same volume of wort, because more water is absorbed by the grains in the larger grain bill. But the increase in water is not exactly proportional... you have to account for the higher grain absorption, but the rest of the water requirement doesn't change.

OTOH, if you do increase the water proportionally, you would end up with the same mash efficiency as with the smaller grain bill, but you'd also end up with more pre-boil wort, which you'd have to boil longer to reach your desired post boil volume.

(For simplicity, I'm ignoring other constants, like mash tun dead space, etc.)

 

[corkybstewart]

My take is that you can do all the measuring and calculating you want, but on brewday nothing will turn out exactly as you expect. Not on homebrewing scale, not on Budweiser scale. Budweiser uses super tasters to blend batches in order to maintain uniformity, because they know that each combination of grains, hops and yeast will give results slightly different than their master calculators figure. Over my years of homebrewing I quit sweating the .001 SG differences between what I expected and what I got. The beer was good regardless.

 

[corkybstewart]

And on a further note, being able to identify the divergence from what you expected and adapt to end up with the beer you wanted is the mark of a good homebrewer. Brew on!

 

[Miles_1111]

No, it's based on having the same amount of wort run off from the mash. There will be more total water for the larger grain bill to get that same volume of wort, because more water is absorbed by the grains in the larger grain bill. But the increase in water is not exactly proportional... you have to account for the higher grain absorption, but the rest of the water requirement doesn't change.

OTOH, if you do increase the water proportionally, you would end up with the same mash efficiency as with the smaller grain bill, but you'd also end up with more pre-boil wort, which you'd have to boil longer to reach your desired post boil volume.

(For simplicity, I'm ignoring other constants, like mash tun dead space, etc.)

If I understand correctly, the larger the grain bill, the larger the grist absorption rate ( for some unknown reason, which cause things not proportional ) , so if I want to get the same pre-boil volume, increase total water proportionally will only lead to low efficiency, low OG.

BTW, I am doing BIAB and no sparge.

 

[VikeMan]

If I understand correctly, the larger the grain bill, the larger the grist absorption rate ( for some unknown reason, which cause things not proportional ) ,

The absorption rate, i.e. gallons per pound, doesn't change. But the total amount absorbed does.

so if I want to get the same pre-boil volume, increase total water proportionally will only lead to low efficiency, low OG.

If you increase water proportionally, you don't pay an efficiency penalty. If you increase water just enough to cover the increase in total grain absorption, then efficiency will be lower.

 

[Miles_1111]

The absorption rate, i.e. gallons per pound, doesn't change. But the total amount absorbed does.

If you increase water proportionally, you don't pay an efficiency penalty. If you increase water just enough to cover the increase in total grain absorption, then efficiency will be lower.

How should I fix it then? After I input the grain bills in Beersmith, it calculate the total mash water needed according to the my brew system profile I input ( such as mash efficiency ) beforehand. Should I prepare different brew system profiles in the sofeware with different mash efficiencies in ordre to brew batches with different grain bills. Say at 5%, 6%, 7% and 8% ABV use different brew system profiles with different efficiency?

 

[doug293cz]

How should I fix it then? After I input the grain bills in Beersmith, it calculate the total mash water needed according to the my brew system profile I input ( such as mash efficiency ) beforehand. Should I prepare different brew system profiles in the sofeware with different mash efficiencies in ordre to brew batches with different grain bills. Say at 5%, 6%, 7% and 8% ABV use different brew system profiles with different efficiency?

BeerSmith does not try to compensate for the lower lauter efficiency (one component of mash efficiency, the other is conversion efficiency) of larger grain bills for the same pre-boil volume. Everything @VikeMan has said in this thread is correct, and specifically applies to lauter efficiency. One thing he hasn't mentioned is that if the conversion efficiencies are different between batches, then that will confound the lower lauter efficiency of larger grain bills. Mash efficiency = conversion efficiency * lauter efficiency. The larger grain bill effect only affects lauter efficiency.

BeerSmith estimates mash efficiency (and with that pre-boil SG and OG) starting from the BrewHouse efficiency that you input to BeerSmith. If you don't adjust your brewhouse efficiency input based on grain bill size, then BeerSmith will give you flaky numbers. It is possible to get pretty accurate estimates of lauter efficiency based on water volumes and grain bill size and potential for a given lautering process. But as noted, BeerSmith does not attempt to do this. The Priceless BIAB calculator does correctly compensate for the grain bill size effect on lauter efficiency, as does my spreadsheet. There are probably others as well.

Brew on

 

[doug293cz]

With my system - i calculate my strike volume based on the total grain bill. My last brew was my biggest grain bill ever (still not huge) but my mash efficiency was also my highest to date - at 84ish IIRC. I had been running in the 78 range for lower ABV brew.

Unless you calculate both conversion efficiency and lauter efficiency, you can't make a valid conclusion from your observations. Lauter efficiency can go down, but an increase in conversion efficiency can more than make up for the reduction in some cases.

Brew on

 

[object]

High alcohol generally means high OG. To achieve high OG you need to use more grains and one of two strategy:
1. You can reduce water-to-grist ratio and sparge volume, so your preboil wort is thick, but grain keeps a lot of sugars going down the drain, lowering efficiency.
2. You can keep normal water-to-grist ratio and sparge volume, but you collect more preboil wort (thus you need a huge tun) of much lower gravity, so you need to extend boiling significantly to reach desired OG.

I just made Doppelbock this night using the second strategy, so I had to boil 8.5 hours to reach OG 1.139. Exhausting but I hit desired efficiency of 92% (100% is the maximum malt extraction specified by the maltier).

There was a clever strategy used in past. When you want a big beer, you collect the first wort without sparge and boil it for your big big. Then you sparge once and collect the second wort and boil if for a middle beer of normal gravity. Then you sparge for the second time, collecting wort for a small table beer of low gravity. So that allows you to squeeze all the sugars from the grain, your total efficiency is high, and boiling time of each beer is reasonably short.

 

[VikeMan]

Unless you calculate both conversion efficiency and lauter efficiency, you can't make a valid conclusion from your observations. Lauter efficiency can go down, but an increase in conversion efficiency can more than make up for the reduction in some cases.

This is true, but I'd add that something has to cause that increase in conversion efficiency. Using the same process won't, i.e. "there's no free lunch" here.

 

[VikeMan]

How should I fix it then?

You could use @doug293cz's sheet to estimate the change in efficiency. If you're otherwise happy with BeerSmith, that's what I'd recommend. Or you could use BrewCipher (which would replace Beersmith), which has a built-in mash efficiency prediction function. Doug also mentioned the Priceless calculator. I'm not familiar with it, but if Doug recommends it, it's good.

 

[JohnnyO']

Unless you calculate both conversion efficiency and lauter efficiency, you can't make a valid conclusion from your observations. Lauter efficiency can go down, but an increase in conversion efficiency can more than make up for the reduction in some cases.

Brew on

Agree. No conclusion was made.

 

[slurms]

The numbers on the side of the kettle are pretty easy to read, though.

If these were put on by the manufacturer, double check the accuracy of them. The gallon markers on my kettle are spaced slightly farther apart than one gallon, compounding the error my over a half gallon when the kettle is mostly full. But as you said, it would be a consistent error (if it is one) in this case.

 

[JohnnyO']

If these were put on by the manufacturer, double check the accuracy of them. The gallon markers on my kettle are spaced slightly farther apart than one gallon, compounding the error my over a half gallon when the kettle is mostly full. But as you said, it would be a consistent error (if it is one) in this case.

I did just that. The markings did not agree with the markings on three of my other vessels. Off 0.25 gal at around 6. I informed the Mfr - and they said thanks.