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Mash efficiency - before and after sparge.

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paddy.odwyer

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Hi there,

I'm very new to mash efficiency (and brewhouse efficiency as well for that matter) and I wanted to gain some insight as to how you measure this effiency, namely, do you do it before or after sparging.

For example, I just did a BIAB clone recipe of Young Henry's Newtowner Pale Ale.

I mashed with 23L of water, and then dunk sparged the bag into 8L of water. I took a gravity reading directly after the mash, which was 1.051, and then also after combining the sparge water to the mash, which was 1.044. This makes sense to me, as the sparge water would be diluting the mash, and therfore reducing the specific gravity reading.
So far, I've used a total of 31L water. However, after adding this sparge water, my total pre-boil volume was 27L, therefore I lost 4L to grain absorption (which was expected because I had roughly 4.5KG of grains, and squeezed the bag both after mashing and sparging.

Because I had these two readings at my disposal, when I tried to calculate my mash efficiency, I decided to do it both before and after the sparging process.
So, I took the PPG of each of the grains, multiplied them by their respective grain bills (in pounds), and then divided it by each specific volume. So for the BEFORE SPARGE efficiency reading, I divided by 6.08 gallons, and for AFTER SPARGE I divided by 8.19 gallons.

What I found shocked me and I can't quite figure out the math.

BEFORE SPARGE efficiency was 51/62.5 = 81.6%, this seems normal to me. But AFTER SPARGE, was 44/46.4 = 94.8%.

Is this purely because I'm accounting for all the water being used, or is there something more complicated occurring here?

Apologies if this is blindingly obvious maths...Like I said, I'm new to the efficiency game, and its kind of boggling my mind a bit hahaha.

Cheers, Paddy.
 

philrob

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It's possible to do the work by longhand calculations, but most these days will use some kind of brewing software. Personally, I use BeerSmith 3, but there are others, including free ones.

If you are really interested in twisting yourself into knots and doing it the long way, post back and I can let you have some material I have saved, including some from a talk given by MHB at an HUB meeting.
 

kadmium

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You multiply the volume x the gravity and divide by the weight of grain, all in imperial.

Then you need to work out potential for the batch, and work out what you got divided by potential.

Or use this:

 

MHB

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I use software (well I spreadsheet I put together), doing it all long hand is tedious but I think its good to be able to. When kids go to school they get taught long division before getting a Casio to make like easier.
Unless we understand the principals underpinning what we are doing we don't have an understanding of the processes nor control of them.

Paddy, its so much easier to do in metric.
The modern method uses Potential instead of PPG. If a malt is said to have a CGAI (Coarse Grind As Is) potential of say 77% from 1kg of that malt in a perfect world you could get 0.77kg of extract, any less is your efficiency.
All the information available on malts made or sold (in theory) in Australia will be expressed in % Potential, sometimes its expressed as % of Dry Fine, then there will be a Moisture Content (again as %) and a Coarse/Fine difference. Some UK maltsters still give the old IOB Method results (Institute of Brewers).
PPG is based on Sugar (Sucrose) being a pound of sugar in a gallon of water (US units) the yield being 42 PPG (the sg of a 1ppg solution would be 1.042)
If you have a malt that yields for instance 37ppg its potential would be 37/42*100=88.1%

Nothing wrong with getting yields in the high 90%'s however I have noticed that there is a real increase in tannins (astringency) in most beer when people are getting much over 85%, unless real care is taken with sparge temperature and sparge water mineral content and pH. The pursuit of high efficiency easily reach the point where you get more of crappy beer.
Good idea to taste very critically and not push your processes too far, malt is cheap compared to everything else that goes into a brew.
Mark

PS
kadmium, Handy enough little calculator
there is a units button down the bottom - switch to metric
M
 

kadmium

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Yeah, I'm all for simple online calculators. I'm a simple man!

But agreed need to know why we are calculating rather than just doing it.

On a side note, gave my grain mill its first run today. I ended up with 62% mash efficiency and 54% BH.

Damn. Ah well, will need to dial in the mill and my processes.
 

paddy.odwyer

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It's possible to do the work by longhand calculations, but most these days will use some kind of brewing software. Personally, I use BeerSmith 3, but there are others, including free ones.

If you are really interested in twisting yourself into knots and doing it the long way, post back and I can let you have some material I have saved, including some from a talk given by MHB at an HUB meeting.
Dear Phil,

Thanks for your response.

The maths itself is not so much the issue for me but rather I am unsure which volumes I should be using when doing the calculations. For example. If i want to get my mash efficiency for my total mash+sparge, then should I take the PPG (or potential) of my grains at 31L (8.19 gallons) of water, (aka, the total amount of water used), or at 27L (7.13 gallons) (aka, the pre-boil volume, because 4L was absorbed by the grain)?

The two volumes, when calculated for mash efficiency, give two very different final efficiencies, and I'm just curious which is the more correct way to calculate it.

Thanks, Paddy.
 

paddy.odwyer

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You multiply the volume x the gravity and divide by the weight of grain, all in imperial.

Then you need to work out potential for the batch, and work out what you got divided by potential.

Or use this:

Thanks Kadmium,

However I'm still unsure what constitutes the volume in that equation you listed, is this total water used after mashing and sparging, or is it merely the preboil volume (which would not be including water lost to grain absorption)? Like I said to Phil, these two volumes when calculated for mash efficiency, yield two very different final efficiencies.

Cheers, Paddy.
 

paddy.odwyer

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I use software (well I spreadsheet I put together), doing it all long hand is tedious but I think its good to be able to. When kids go to school they get taught long division before getting a Casio to make like easier.
Unless we understand the principals underpinning what we are doing we don't have an understanding of the processes nor control of them.

Paddy, its so much easier to do in metric.
The modern method uses Potential instead of PPG. If a malt is said to have a CGAI (Coarse Grind As Is) potential of say 77% from 1kg of that malt in a perfect world you could get 0.77kg of extract, any less is your efficiency.
All the information available on malts made or sold (in theory) in Australia will be expressed in % Potential, sometimes its expressed as % of Dry Fine, then there will be a Moisture Content (again as %) and a Coarse/Fine difference. Some UK maltsters still give the old IOB Method results (Institute of Brewers).
PPG is based on Sugar (Sucrose) being a pound of sugar in a gallon of water (US units) the yield being 42 PPG (the sg of a 1ppg solution would be 1.042)
If you have a malt that yields for instance 37ppg its potential would be 37/42*100=88.1%

Nothing wrong with getting yields in the high 90%'s however I have noticed that there is a real increase in tannins (astringency) in most beer when people are getting much over 85%, unless real care is taken with sparge temperature and sparge water mineral content and pH. The pursuit of high efficiency easily reach the point where you get more of crappy beer.
Good idea to taste very critically and not push your processes too far, malt is cheap compared to everything else that goes into a brew.
Mark

PS
kadmium, Handy enough little calculator
there is a units button down the bottom - switch to metric
M
Thanks very much for all your helpful information Mark. I will definitely use this method instead next time I calculate my efficiency. However, as I've mentioned above, I'm still just unclear whether the volume I should be using in my calculation is the total volume of water used for mashing and sparging (31L), or the pre-boil volume I had in my kettle prior to boiling (27L, which would be omitting the water lost to grain absorption).

When calculating mash efficiencies using these two volumes, you get two very different results as I stated in my initial thread, and I would love for someone to tell me which of these two volumes is the standard and to explain why there is variances in the efficiencies between these two volume options...because I know deep down it is simply mathematical, but can't quite figure out why it happens.

Kind regards, Paddy.
 

MHB

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Usually its "Kettle Full" the volume in the kettle when you have collected everything you are going to get.
Remember to correct for Temperature, both SG and Volume are affected, wort contracts about 4% between 100 and 20oC. So at mash out (~80oC) there will be about 3% more volume, 27L at 80oC is really 26.19L at 20oC, might not sound like much but all the little bits add up.
Once you have all that
Mass of extract = V*SG*oP (or very roughly from OP) Mass = 27*1.044*0.11 gives about 3.1kg of extract.
If you used 4.5kg of malt that had a 76% potential there was about 3.42kg
Efficiency is 3.1/3.42*100 = 90.6% That's really rough little more than finger counting really, just to show the method. Far from confidant that the potential is 76%, that the grain bill was exactly 4.5kg and that you got 27L (temp corrected) into the kettle.
But the numbers you are getting are close to right so looks like you aren't doing too much wrong.
Mark
 

philrob

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Mark has explained it all perfectly.
Nothing I can add, really.
 

paddy.odwyer

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Usually its "Kettle Full" the volume in the kettle when you have collected everything you are going to get.
Remember to correct for Temperature, both SG and Volume are affected, wort contracts about 4% between 100 and 20oC. So at mash out (~80oC) there will be about 3% more volume, 27L at 80oC is really 26.19L at 20oC, might not sound like much but all the little bits add up.
Once you have all that
Mass of extract = V*SG*oP (or very roughly from OP) Mass = 27*1.044*0.11 gives about 3.1kg of extract.
If you used 4.5kg of malt that had a 76% potential there was about 3.42kg
Efficiency is 3.1/3.42*100 = 90.6% That's really rough little more than finger counting really, just to show the method. Far from confidant that the potential is 76%, that the grain bill was exactly 4.5kg and that you got 27L (temp corrected) into the kettle.
But the numbers you are getting are close to right so looks like you aren't doing too much wrong.
Mark
Thanks so much for this, its really clearer everything up and I definitely feel ready to implement these tools into my next brew. But one final clarifying question if you don't mind.

Its about wort contraction due to temperature. Does that mean when you take a post mash SG reading, that gravity reading specifically relates to a volume that is roughly 4% less than the amount currently in your kettle? Like, say after a mash it looks like you have 27L, so you take a little sample and cool that sample down and take a gravity reading...that gravity reading is actually based off a volume of roughly 26.2L, not 27L?

Cheers, Paddy.
 

philrob

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Yes. You are correct about the volume.
 
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MHB

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Yep
But its going to be closer to 3% less volume at 80oC. The 4% is the standard number used to calculate contraction from boiling (100oC) to 20oC. There are tables and equations you could look up.

20oC is used as a "standard" reference temperature, it's used for the density, pH, colour... its where everything is measured, bit like percent (x/100) is used as a universal fraction.
Mark
 

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