Thoughts on conversion efficiency over 100%

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ScrewyBrewer

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While most of my recipes have a conversion efficiency in the near 93-100% range, there are a few outlier recipes that were 102%. My thoughts are that one or more of the mashed grains had a higher than expected starch contribution, or possibly the result is due to a plus or minus 2% error factor.

Are there other explanations for getting higher than 100% conversion efficiency?
 
a plus or minus 2% error factor.

Very likely.

Do you mix up the wort thoroughly before taking a sample?

How are you measuring and from where do you take the sample?

How do you measure volumes? Do you correct all volumes for temperature expansion to room temp before any calculations?

Also, most extraction rates for malt are listed as minimums. 2% over isn't much of a variance.

Best is to brew the same beer with the same malts a few times. If you repeat the same measurements you know what you're looking at.
 
Is there anything common about the outlier recipes that is absent from your typicals? Different base malt? High adjunct? Sugar addition? Sparge volume? Anything?
 
Both batches are 5 gallon BIAB batches, bag squeezed and no sparge water used, 8.8% and 9% ABV Baltic Porters, with 4 ounces of hops in a pH range of 5.52-5.54 with post boil volumes of 6.65 gallons.

The 102% conversion recipe has (20 lbs of grain) 35.50 pts/lb/gal weighted potential and 11 lbs of Montana 2-Row malt.

The 99% conversion recipe has (21.50 lbs of grain) 35.90 pts/lb/gal weighted potential and 6.25 lbs Vienna Malt and 6.25 lbs Montana 2-Row malt and .25 lb of Black Malt.

All other grains are the same in both recipe although in different percentages.
 
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The 102% conversion recipe has 559 points recovered, 9.821 gallons actual water, 8.208 gallons pre-boil volume and 1.0682 pre-boil gravity.

The 99% conversion recipe has 539 points recovered, 9.396 gallons actual water , 7.896 gallons pre-boil volume and 1.0683 pre-boil gravity.
 
Experimental error for sure. There is uncertainty in every step of the brewing process - accuracy of weighing grain and measuring water/wort volumes, uncertainty in how much extract each grain can actually contribute, error in actually measuring gravities, etc, etc. These all add up. I would be impressed if a homebrewer was actually within 5-10% error.
 
Is the 20# the actual amount of grain or 11#? Same with the other beer. You call out 12.75# but also 21.5.
All other grain types are the same in both recipes, although in different percentages.

The 102% recipe uses 11# Montana malt and the 99% recipe uses a mix of 6.25# Vienna malt and 6.25# Montana malt.
 
102% Conversion Efficiency
conv eff.jpg

99% Conversion Efficiency
 
Experimental error for sure. There is uncertainty in every step of the brewing process - accuracy of weighing grain and measuring water/wort volumes, uncertainty in how much extract each grain can actually contribute, error in actually measuring gravities, etc, etc. These all add up. I would be impressed if a homebrewer was actually within 5-10% error.
It is a matter of knowing whether exceeding 100% conversion is at all possible under any conditions, when all measurements are accurate.
 
As to that direct question, yeah. In my first response I mentioned that reported extraction rates are typically minimums.

You know 100% conversion is possible. If the malt provides an actual 38 vs the reported min 37, there you go. You got 38 instead of 37. More than 100%.
 
As to that direct question, yeah. In my first response I mentioned that reported extraction rates are typically minimums.

You know 100% conversion is possible. If the malt provides an actual 38 vs the reported min 37, there you go. You got 38 instead of 37. More than 100%.
Thank you for taking the time to dig into the details of my question and replying with an answer. I feel like I have a handle on the components of mash efficiencies now, and it is always helpful to get someone else's thoughts on the matter.
 
:mug:

For what it's worth, I haven't yet squared your numbers in software. Not to say they're inaccurate, I just haven't been able to duplicate them. For the exercise, I'll probably play with them more tonight. I'm weird, I like the math puzzle.
 
The only way to actually get more than 100% conversion efficiency is for the listed grain potential to be less than the actual grain potential of the malt used.

But, then you didn't really get over 100% efficiency, because the data was wrong.

So, if all of the data and measurements are correct, including grain potential, you cannot get more than 100%.

There is room for questioning whether or not the Congress mash really extracts all of the potential of the grain. If it doesn't then brewers could routinely get apparent conversion efficiencies greater than 100%.

Brew on :mug:
 
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With the numbers provided, I work out the following:

Batch 1 (102%)
EffConversion 94.34
EffLauter 83.58
EffMash 78.84

Batch 2 (99%)
EffConversion 83.14
EffLauter 84.04
EffMash 69.87

Your points recovered work out, but using your reported volumes and ppg potentials your efficiencies do not. For me, at least.
 
I did some goal seeking with my spreadsheet, and to get a post-mash SG of 1.0682 with 20 lb of grain, 9.821 gal of strike water, and 100% conversion efficiency requires a dry basis weighted grain potential of 1.0394 (85.4%), which seems highly unlikely.

1641782161173.png
1641782280553.png


Notes:
  1. Setting "Boil Time" or "Boil-off Rate" to 0 turns "Post-Boil Volume" into Pre-Boil Volume
  2. "Total Brewing Water" equals strike volume for no-sparge
How are you calculating your conversion efficiency?

Brew on :mug:
 
I did some goal seeking with my spreadsheet, and to get a post-mash SG of 1.0682 with 20 lb of grain, 9.821 gal of strike water, and 100% conversion efficiency requires a dry basis weighted grain potential of 1.0394 (85.4%), which seems highly unlikely.

How are you calculating your conversion efficiency?

Brew on :mug:
Below are the parameters I entered based on the 102% conversion efficiency for the recipe. This produced a lauter efficiency of 74.62% and a mash efficiency of 76.11%.

I struggled with the formula discussed here to calculate conversion efficiency so I manually adjusted the 102% value to align with the Post-Boil / Pre-Boil Volume. Once entered I confirm the conversion efficiency by dividing the converted extract weight by the potential extract weight.



conveff-a.jpg


conveff-b.jpg
 
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As to that direct question, yeah. In my first response I mentioned that reported extraction rates are typically minimums.

You know 100% conversion is possible. If the malt provides an actual 38 vs the reported min 37, there you go. You got 38 instead of 37. More than 100%.

Yes, exactly. When you look at the malt data sheet, it will give you a minimum extraction, and it varies from lot to lot, so it can definitely be that simple.
 
Yes, exactly. When you look at the malt data sheet, it will give you a minimum extraction, and it varies from lot to lot, so it can definitely be that simple.
I see now how changes to the FGDB and grain moisture percentages will also change the mash run-off gravity. My takeaway from this thread is when conversion efficiency exceeds 100%, FGDB and grain moisture adjustments are needed.

Sometimes the simple answers are the best thank you.
 
@ScrewyBrewer, if your volumes are accurate I would highly doubt your gravity measurements. The way I figure it, you'd need conversion up around 111%. That's just not likely.

Simple answers are best. Likely a (or more) measurement errors.

What was the post-boil gravity of Batch1?
 
@ScrewyBrewer, if your volumes are accurate I would highly doubt your gravity measurements. The way I figure it, you'd need conversion up around 111%. That's just not likely.

Simple answers are best. Likely a (or more) measurement errors.

What was the post-boil gravity of Batch1?
The post-boil volume was 6.646 gallons and the post-boil gravity was 1.0811. I brewed this batch in September and after fermentation there was enough volume to fill a 5-gallon keg.

porterOG.jpg
 
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Hmm. I would have expected a refractometer as you report your gravities to the fourth digit.

Your pre- and post-boil gravity points don't quite match. That clues us in that there's at least some measurement inaccuracy.

What method(s) do you use to measure volumes?
 
Hmm. I would have expected a refractometer as you report your gravities to the fourth digit.

Your pre- and post-boil gravity points don't quite match. That clues us in that there's at least some measurement inaccuracy.

What method(s) do you use to measure volumes?
When you say the pre and post-boil gravities do not match, I am not sure why you think that. The values posted come from a spreadsheet, but my measurements are more back of the envelope on brew day. There were no noticeable volume measurement errors when filling the fermentor or the keg, as the volumes were in line with previous batches.

conveff-2.jpg
 
But, how do you actually measure the water? Input water by weight? Markings on the kettle with quart gradations? A ruler measuring wort height to the 1/8" with the finding plugged into the formula for the volume of cylinder?

VolPre-boil*GravPre-boil should equal the same post-boil. Yours are close, but not the same.

ETA:
8.21*68.2=559.79
6.65*81.1=538.99
 
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But, how do you actually measure the water? Input water by weight? Markings on the kettle with quart gradations? A ruler measuring wort height to the 1/8" with the finding plugged into the formula for the volume of cylinder?

VolPre-boil*GravPre-boil should equal the same post-boil. Yours are close, but not the same.
I have done BIAB brewing regularly on this system since 2014 and have dialed in wort losses for dead space, evaporation, and fermentor. I measure strike water using a 1-gallon pitcher with quart increments, and the kettle is marked in 1-gallon increments.

I am not familiar with the formula you shared above as written. Could you further explain it using the numbers I posted?
 
I have done BIAB brewing regularly on this system since 2014 and have dialed in wort losses for dead space, evaporation, and fermentor. I measure strike water using a 1-gallon pitcher with quart increments, and the kettle is marked in 1-gallon increments.

With all respect, that does not provide very accurate numbers. All the volumes you've provided to the hundredths aren't actually measured, they're calculated? That's your issue right there. It's more likely for your volumes to be off than for the maltster to undersell their malt by 10%.

I measure all my volumes with a ruler to the nearest mm and solve for the volume of a cylinder. With my kettle, that gives me accuracy to the nearest ~1.7oz. My calculations are therefore rather accurate, but there's still a bit of variance.

Sugar follows the laws of conservation. If you recover 100pts and start with 1gal of wort with a gravity of 50 (1.050) and reduce it in half, the resulting 1/2gal will have a gravity of 100 (1.100). The total gravity points don't change.
 
The precision of various measurements is far below the 4-significant-digit figures in these calculations, notably liquid volumes. No uncertainty / error bars are shown. Clearly the OP's conversion efficiency is great. While it's understandable to scratch one's head about exceeding 100%, perhaps the nose is too close to the page here?

Brew on!
 
That's not clear at all.
20 plus pounds of malt for a 5 gallon batch might reasonably be expected to yield lower numbers. In this case I mean "great" as subjective, i e. in the mind of the brewer, who believes in numbers around 100%, which *clearly* must feel great. But y'all can chew on the numbers and formulas of course. Enjoy!
 
Is this Batch1 (102%)? You reported a pre-boil of 8.21 on that.
Other than the grain types and amounts, I found another difference between the two batches I missed earlier in this thread. I hope this helps clear up some confusion rather than adding to it.

It seems batch1 (102%) boiled for 1-hour requiring 7.896 gallons of pre-boil wort.
conveff-5d.jpg


But batch2 (99%) was boiled for 1.25-hours requiring 8.208 gallons of pre-boil wort.
conveff-5c.jpg


@DBhomebrew thank you for providing another way to look at my results.
 
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Below are the parameters I entered based on the 102% conversion efficiency for the recipe. This produced a lauter efficiency of 74.62% and a mash efficiency of 76.11%.

I struggled with the formula discussed here to calculate conversion efficiency so I manually adjusted the 102% value to align with the Post-Boil / Pre-Boil Volume. Once entered I confirm the conversion efficiency by dividing the converted extract weight by the potential extract weight.



View attachment 755157

View attachment 755158
Looks like you have some errors when using my spreadsheet. I am at least partially to blame, as I haven't provided much in the way of instructions on proper use.

If you enter a % Fine Grind Dry Basis Grain Potential, it overrides the PPG value (if any) entered directly above it. You would have to look at the formula for % Extract Potential (Dry Basis) under Derived Values to know this. If you look at this value in the example you posted screen shots for, it should be 80%, as that's what you entered in the input section. So your calculations were actually for a PPG of 37 rather than the 35.5 that you entered.

Also, you used strike water volume of 9.396 gal, whereas in your previous post you listed your strike volume as 9.821 gal, which is a significant difference.

If I rerun your case, removing the 80% FGDB potential so that the sheet actually uses 35.5 PPG, I get your apparent mash efficiency at 106%

1641841530493.png

1641841688845.png


Brew on :mug:
 
@DBhomebrew I enter 80% FGDB by default even though calculating the pts/lb/gal for the recipe, the mash and lauter differences between the two are about 0.25%.

Here are the actual numbers I have.

20.00 lbs grain
35.50 pts/lb/gal
1.900 qts/lb mash thickness
9.500 gal strike water
9.396 gal actual strike water (7.896 pre-boil + 1.5 grain abs = 9.396 gal)
68.2 (1.0682) Reported preboil gravity
710.0 theoretical gravity pts in mash = 20 lbs * 35.50 pts/lb/gal
681.8 potential points = 20 lbs * 35.50 pts/lb/gal * (1 - 0.04 moisture)
538.5 points recovered = 7.896 pre-boil vol * 68.2 ppg
19.20 lbs dry grain weight = 20 lbs * (1 - 0.04 moisture)
Potential extract:
15.360 lbs = .80 FGDB potential * 19.20 lbs dry grain weight
Converted extract:
15.667 lbs = 1.02 (102%) * 15.360 lbs
102% conversion eff = 15.667 potential / 15.360 converted extract
 
@doug293cz the 35.50 pts/lb/gal are calculated as an average of 9 different types of grain in the recipe.

The difference between entering 80% FGDB or 35.5 pts/lb/gal changes the mash and lauter efficiencies by 0.25% and the points recovered by 19 points. The SG based on 80% FGDB and 4% moisture content is 1.0353 (35.3 pts/lb/gal).

The correct strike water volume is 9.396 gallons, there were some mistakes made on my part when entering all the values today.

In your estimation which entry is the more reliable one, entering the FGDB percentage or the calculated 35.5 pts/lb/gal value?
 
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@DBhomebrew I enter 80% FGDB by default even though calculating the pts/lb/gal for the recipe, the mash and lauter differences between the two are about 0.25%.

Here are the actual numbers I have.

20.00 lbs grain
35.50 pts/lb/gal
1.900 qts/lb mash thickness
9.500 gal strike water
9.396 gal actual strike water (7.896 pre-boil + 1.5 grain abs = 9.396 gal)
68.2 (1.0682) Reported preboil gravity
710.0 theoretical gravity pts in mash = 20 lbs * 35.50 pts/lb/gal
681.8 potential points = 20 lbs * 35.50 pts/lb/gal * (1 - 0.04 moisture)
538.5 points recovered = 7.896 pre-boil vol * 68.2 ppg
19.20 lbs dry grain weight = 20 lbs * (1 - 0.04 moisture)
Potential extract:
15.360 lbs = .80 FGDB potential * 19.20 lbs dry grain weight
Converted extract:
15.667 lbs = 1.02 (102%) * 15.360 lbs
102% conversion eff = 15.667 potential / 15.360 converted extract
@doug293cz the 35.50 pts/lb/gal are calculated as an average of 9 different types of grain in the recipe.

The difference between entering 80% FGDB or 35.5 pts/lb/gal changes the mash and lauter efficiencies by 0.25% and the points recovered by 19 points. The SG based on 80% FGDB and 4% moisture content is 1.0353 (35.3 pts/lb/gal).

The correct strike water volume is 9.396 gallons, there were some mistakes made on my part when entering all the values today.

In your estimation which entry is the more reliable one, entering the FGDB percentage or the calculated 35.5 pts/lb/gal value?
The thing is, entering 80% FGDB overrides the 35.5 PPG that you calculated for the recipe, and you end up with the same result as if you had entered 37.0 PPG.

You should enter whichever one you have better data for.

The recommended strike volume is higher than the actual strike volume because your maximum desired mash thickness is thinner than the strike volume needed to hit your target pre- and post-boil volumes, so the sheet picks the number needed to hit your target volumes. The max mash thickness comes into play when splitting water between strike and sparge.

The spreadsheet was designed for predictive use, so it is not particularly convenient for working with actual brew day measurements. Reconcile actual measurements and back calculate things like conversion efficiency, grain absorption rate, etc. by judicious use of the "Goal Seek" tool in Excel or OpenOffice (but not in Google Sheets.) For example to calculate actual conversion efficiency:
  1. Open the "Goal Seek" tool
  2. Select the Initial Run Off SG cell as the Formula Cell
  3. Enter your actual initial run off SG as the target value
  4. Select the Conversion Efficiency input cell as the variable cell
  5. Run the Goal Seek

Brew on :mug:
 
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