Thoughts on conversion efficiency over 100%

[ScrewyBrewer]

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?

 

[DBhomebrew]

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.

 

[ScrewyBrewer]

@DBhomebrew let's presume all measurements are recorded accurately for multiple batches.

 

[DBhomebrew]

Is there anything common about the outlier recipes that is absent from your typicals? Different base malt? High adjunct? Sugar addition? Sparge volume? Anything?

 

[ScrewyBrewer]

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.

 

[DBhomebrew]

And for each of those, actual total water volumes? Actual pre-boil volumes? Actual pre-boil gravities?

 

[ScrewyBrewer]

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.

 

[hopjuice_71]

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.

 

[DBhomebrew]

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

Is the 20# the actual amount of grain or 11#? Same with the other beer. You call out 12.75# but also 21.5.

 

[ScrewyBrewer]

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.

 

[ScrewyBrewer]

102% Conversion Efficiency

99% Conversion Efficiency

 

[ScrewyBrewer]

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.

 

[DBhomebrew]

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%.

 

[ScrewyBrewer]

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.

 

[DBhomebrew]

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.

 

[doug293cz]

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

 

[DBhomebrew]

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.

 

[doug293cz]

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.

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

 

[ScrewyBrewer]

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

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.

 

[Yooper]

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.

 

[ScrewyBrewer]

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.

 

[DBhomebrew]

@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]

@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.

 

[DBhomebrew]

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?

 

[ScrewyBrewer]

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.

 

[DBhomebrew]

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

 

[ScrewyBrewer]

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?

 

[DBhomebrew]

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.

 

[ScrewyBrewer]

If my formula is correct, and I think it may be, below are the results I get.

 

[DBhomebrew]

If my formula is correct, and I think it may be, below are the results I get.

View attachment 755178

Is this Batch1 (102%)? You reported a pre-boil of 8.21 on that.