Recipe calls for more sparge water than mash water?

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RickyBeers

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Planning to start my grainfather at 4am tomorrow for very basic American Light Lager.

Recipe:
Pilsner 6.5lb
Corn, flaked 1.35lb
Corn sugar (late addition) .5lb
Voss Kveik yeast, 1 pack dry

Mash step 1
147F 75min
Mashout
165F 10 min

Boil 90 min
60 min hallertau .5oz
10 min hallertau .5oz

Final batch size 5.5 USG

Mash water - 3.47 USG
Sparge water - 4.11 USG
Total water - 7.58 USG

I have brewed this beer before, and it was great. I used 5.2 stabilizer (which, I know, everyone hates that stuff)

My last 5 brews I have been off and on with astringency issues. Very depressing tossing a batch that's undrinkable. Before I started getting into water chemistry, I had never heard of astringency, and now of course as I stop the 5.2 and play with brewing salts, I begin to have issues. I also had a stuck sparge for the first time, which I believe also caused issues.

Tomorrow, I'm going to try the 5.2 stabilizer again, but I'm also spooked about that amount of sparge water, since sparging is also a astringency culprit.

I checked the recipe on both the grainfather app, and brewsmith, both had more sparge water than mash. Am I safe to follow it? Or should I just use my total water, add 5 gallons for mash, and sparge with the remaining 2.58?
 
My opinion is that water values listed in recipes should be ignored. Well, maybe not fully ignored but always adapted to your system and process. In the past, it was very common to mash with 1.25 or 1.3 qts of water per lb of grain and sparge with the rest. With BIAB (bag or basket) it is much more common to mash with a much higher ratio of water, or to do a full volume mash with all the water.

Mashing with 5 gallons of water and sparging with the rest seems fine.
 
American Light Lager per the style is a fairly low ABV beer. The more sparge water than what you think normal seems to ensure you won't wind up with a high OG. More OG will mean higher ABV which might not be a light lager anymore.

Just a uneducated guess. But that's what I'm going with till someone comes up with something better.
 
American Light Lager per the style is a fairly low ABV beer. The more sparge water than what you think normal seems to ensure you won't wind up with a high OG. More OG will mean higher ABV which might not be a light lager anymore.

Just a uneducated guess. But that's what I'm going with till someone comes up with something better.
I figured the opposite. I thought sparking increased efficiency. Although, I did end up 4 points higher than expected this morning. Looking like a final product of 4.8% to be expected.
I ended up only sparring with one gallon though. Got too spooked to even do 2.48
 
I always have more sparge water than mash. My standard run for rig I have now is 6.5-7 gallons mash in, 9-9.5 gallons semi fly sparge, for 19-21# grist. 16 gallons total. Yield to BK between 13.5 -14.25 gallons.
 
I thought sparking increased efficiency.
Well it does, but only to a point. If you don't sparge you are leaving sugars on the grain. Then you'll have less efficiency.

I don't do efficiency calculations though myself. Not that I don't see their usefulness.

Thinking about it, most of my brew recipes call for twice the sparge water than mash water. And they aren't low ABV beers. So might be interesting to hear what others say about mashing with more water as opposed to just a third or so of the total water volume.

I'm BIAB and I have at least one pot of sparge water that the bag goes in to briefly for a rinse. Sometimes I rinse it twice using different methods.
 
I always have more sparge water than mash. My standard run for rig I have now is 6.5-7 gallons mash in, 9-9.5 gallons semi fly sparge, for 19-21# grist. 16 gallons total. Yield to BK between 13.5 -14.25 gallons.
That’s nice. I was literally just looking at options for larger batch brew systems. I’m looking to upgrade to an all electric that can make 10.5 gallons into 2 corny keg pressure fermentation rigs
 
for a low gravity beer it is not unusual to have more sparge water than mash water if your system is set to a specific water to grain ratio. With these beers you do risk getting into a range of pH and gravity where you could at least in theory start having to worry about astringency. That range is something like north of 5.8 pH and gravity under 1.010. My understanding is you are probably safe if either under 5.8pH or over 1.010 sg but best to try to keep both parameters in the safe range.

To achieve this you will want to acidify your sparge water (small amount of lactic acid...really small according to calculators I use). You can also check your runoff gravity as you get near end with a refractometer. If your gravity falls below 1.010 you may want to stop sparging and just add water to your brew kettle to reach the right pre boil volume.
 
for a low gravity beer it is not unusual to have more sparge water than mash water if your system is set to a specific water to grain ratio.

Agreed. It's taking pounds of grain, figuring a quarts per gallon, calling that the mash water amount and leaving the rest (whatever that may be) to the sparge.
 
as far as tannin extraction, from sparging....i believe if you keep the temp low on the sparge water like 160f or so, should be alright, even when the ph goes up and gravity gets lower?

and i always mash ~20lbs, in 7 gallons and sparge with ~10....
 
Agreed temperature is reported to be another factor on tannin extraction. I also tend to mash with about 11 gallons of water and sparge with 15 but that is due to mash tun limitation. I mash at just about 1 quart per pound.
 
I need to go back to the drawing board the when it comes to astringency. I set my grain mill to .50 instead of .25, And I tend to attempt to under sparge and never go above 75c. I played around with water chemistry and I’ve used lactic acid. I have a low quality ph meter that I’ll use, and I’ll even use strips, nothing ever seems out of line. Yet, astringency is my number 1 off flavor issue
 
for a low gravity beer it is not unusual to have more sparge water than mash water if your system is set to a specific water to grain ratio. With these beers you do risk getting into a range of pH and gravity where you could at least in theory start having to worry about astringency. That range is something like north of 5.8 pH and gravity under 1.010. My understanding is you are probably safe if either under 5.8pH or over 1.010 sg but best to try to keep both parameters in the safe range.

To achieve this you will want to acidify your sparge water (small amount of lactic acid...really small according to calculators I use). You can also check your runoff gravity as you get near end with a refractometer. If your gravity falls below 1.010 you may want to stop sparging and just add water to your brew kettle to reach the right pre boil volume.

This is 100% correct, all of it, and something I've encountered on a couple recent brews.

I brewed a scottish export where I ended up with 3.5 gallons of mash water to 4.5 gallons of sparge water, and I hit 93% mash efficiency! It was great!! Until the beer was done... and I ended up with a permanently hazy and slightly astringent beer caused by the polyphenols from oversparging grain husks.

The reason you have too much sparge water is because you need to decrease your mash thickness (have more mash water). Beersmith defaults to 1.5 qt/lb I believe, but for small grain bills I usually set mine to 2 qt/lb. You take a minor hit on efficiency but that should always be a lower priority than flavor/quality IMO. Just double click the "mash in" step on your mash tab and you can set your mash thickness manually and it should automatically adjust your sparge water amount.
 
That’s nice. I was literally just looking at options for larger batch brew systems. I’m looking to upgrade to an all electric that can make 10.5 gallons into 2 corny keg pressure fermentation rigs

That is exactly what my rig is now. Electric three vessel made of modified 15.5 gallon kegs.

Between boil off, hot break trub loss, etc, I usually have 10-11.5 gallons going into fermentor, then to two 5G cornys. Not particularly low gravity either, starting gravity usually in the 1.054-8 range, sometimes even .060.

I usually heat sparge water to around 185F, then turn off before sparge, by the time sparge is done grain temp seldom above 165F, no tannin worries but decent sugar extraction.
 
As mentioned above, having more sparge water than mash, is completely normal, and especially so in lower ABV beers. I've actually brewed loads of American Lite Lagers, and I always sparge them like crazy to hit my numbers.

While I don't deny that oversparging, and having a slightly higher pH can cause some astringency issues; what worries me is your stating the beer was undrinkable. I'm worried there may be something else in your process causing this off flavor. Mash pH is more forgiving than you might think, and sparging a few quarts below 1.010 isn't the best technique to produce good beer, but I can't imagine that would render a beer undrinkable.

Pick yourself up some lactic acid, and a pack of calcium carbonate. These 2 things will take you basically everywhere you wanna go in mash pH. After a while you'll be able to guess based on your grain bill, what you need to add ahead of time.
 
I need to go back to the drawing board the when it comes to astringency. I set my grain mill to .50 instead of .25, And I tend to attempt to under sparge and never go above 75c. I played around with water chemistry and I’ve used lactic acid. I have a low quality ph meter that I’ll use, and I’ll even use strips, nothing ever seems out of line. Yet, astringency is my number 1 off flavor issue
Are you acidifying your sparge water? Do you know the alkalinity of your water? As the wort gets less concentrated during a sparge, it loses much of it buffering (ability to maintain it's pH) capacity. Too much alkalinity in the sparge water can raise the pH of the dilute mash to a level that will extract tannins, which cause astringency. A way to guarantee that you will not raise the pH too high during sparging is to treat your sparge water with enough acid (lactic, phosphoric, hydrochloric, sulfuric, with the first two being prefered) to bring the pH down to about 5.6, or so.

Brew on :mug:
 
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Here's the basics on mash water to sparge water volumes for maximizing efficiency. The desired ratios are different depending on whether you are fly sparging or batch sparging. As said early on above, ignore the water volume ratios that the recipe specifies.

When Fly Sparging: Use only as much mash water as you need to get the thickest mash you are comfortable with (able to easily stir at dough in, or recirculate, if your system requires it.) Use the balance of the water needed to reach your target pre-boil volume for fly sparging.

When Batch Sparging: Adjust the strike vs. sparge volumes such that each run-off will be approximately equal volume. For single batch sparge the strike and sparge volumes are:
Strike Volume = Expected Grain Absorption + (Target Pre-Boil Volume / 2)​
Sparge Volume = Target Pre-Boil Volume / 2​
For a double batch sparge the volumes become:
Strike Volume = Expected Grain Absorption + (Target Pre-Boil Volume / 3)​
Sparge Volume = Target Pre-Boil Volume / 3​
It turns out that there is an insignificant difference in efficiency over the range of initial:sparge run-off volume ratio between 60:40 and 40:60, so you don't have to worry about being precise. A simple rule of thumb, that will almost always keep you in the good ratio range, is to use 60% of your total required water for mashing, and 40% for sparging, when doing a single batch sparge. For a double batch sparge use a ratio of 50% : 25% : 25%. For large beers you may need to shift more water to strike in order to maintain a manageable mash thickness.

Brew on :mug:
 
they say needing 'hot' water for the sparge is a myth....you're not supposed to sparge past runnoff of like 1.012 either? are you checking running with something like a refrac?
No but I should be doing that, good point

That is exactly what my rig is now. Electric three vessel made of modified 15.5 gallon kegs.

Between boil off, hot break trub loss, etc, I usually have 10-11.5 gallons going into fermentor, then to two 5G cornys. Not particularly low gravity either, starting gravity usually in the 1.054-8 range, sometimes even .060.

I usually heat sparge water to around 185F, then turn off before sparge, by the time sparge is done grain temp seldom above 165F, no tannin worries but decent sugar extraction.

Nice, that sounds great


As mentioned above, having more sparge water than mash, is completely normal, and especially so in lower ABV beers. I've actually brewed loads of American Lite Lagers, and I always sparge them like crazy to hit my numbers.

While I don't deny that oversparging, and having a slightly higher pH can cause some astringency issues; what worries me is your stating the beer was undrinkable. I'm worried there may be something else in your process causing this off flavor. Mash pH is more forgiving than you might think, and sparging a few quarts below 1.010 isn't the best technique to produce good beer, but I can't imagine that would render a beer undrinkable.

Pick yourself up some lactic acid, and a pack of calcium carbonate. These 2 things will take you basically everywhere you wanna go in mash pH. After a while you'll be able to guess based on your grain bill, what you need to add ahead of time.

It's like a punch to the tongue with astringency, I agree it seems crazy. I do have some lactic acid and calcium cabonate, just a bit uneasy to jump into it more since my first batch using salts and lactic acid had that issue as well. Bad excuse though.
 
Are you acidifying your sparge water? Do you know the alkalinity of your water? As the wort gets less concentrated during a sparge, it loses much of it buffering (ability to maintain it's pH) capacity. Too, much alkalinity in the sparge water can raise the pH of the dilute mash to a level that will extract tannins, which cause astringency. A way to guarantee that you will not raise the pH too high during sparging is to treat your sparge water with enough acid (lactic, phosphoric, hydrochloric, sulfuric, with the first two being prefered) to bring the pH down to about 5.6, or so.

Brew on :mug:
I don't acidify my sparge water. I use RO water, so 7 ph. When I was using brewsmith to acidify the sparge water, I thought I remember it seeming like a lot of lactic acid, which of course, concerned me about off flavors...

Here's the basics on mash water to sparge water volumes for maximizing efficiency. The desired ratios are different depending on whether you are fly sparging or batch sparging. As said early on above, ignore the water volume ratios that the recipe specifies.

When Fly Sparging: Use only as much mash water as you need to get the thickest mash you are comfortable with (able to easily stir at dough in, or recirculate, if your system requires it.) Use the balance of the water needed to reach your target pre-boil volume for fly sparging.

When Batch Sparging: Adjust the strike vs. sparge volumes such that each run-off will be approximately equal volume. For single batch sparge the strike and sparge volumes are:
Strike Volume = Expected Grain Absorption + (Target Pre-Boil Volume / 2)​
Sparge Volume = Target Pre-Boil Volume / 2​
For a double batch sparge the volumes become:
Strike Volume = Expected Grain Absorption + (Target Pre-Boil Volume / 3)​
Sparge Volume = Target Pre-Boil Volume / 3​
It turns out that there is an insignificant difference in efficiency over the range of initial:sparge run-off volume ratio between 60:40 and 40:60, so you don't have to worry about being precise. A simple rule of thumb, that will almost always keep you in the good ratio range, is to use 60% of your total required water for mashing, and 40% for sparging, when doing a single batch sparge. For a double batch sparge use a ratio of 50% : 25% : 25%. For large beers you may need to shift more water to strike in order to maintain a manageable mash thickness.

Brew on :mug:
Great explanation. I feel very comfortable with the 60/40 rule of thumb moving forward.

@doug293cz Beat me to the acidify your sparge water ( and also remove any chlorine with a Sod met dose).
Brewersfriend water calculator has an option for setting the pH of your sparge water for your brew.
It's never very much because a few hydrogen ions go a long way in just water.

I'll check out brewersfriend, but also, what is an acceptable amount, 1ml per gallon?
 
I don't acidify my sparge water. I use RO water, so 7 ph. When I was using brewsmith to acidify the sparge water, I thought I remember it seeming like a lot of lactic acid, which of course, concerned me about off flavors...


Great explanation. I feel very comfortable with the 60/40 rule of thumb moving forward.



I'll check out brewersfriend, but also, what is an acceptable amount, 1ml per gallon?
For lactic acid that is
 
I don't acidify my sparge water. I use RO water, so 7 ph. When I was using brewsmith to acidify the sparge water, I thought I remember it seeming like a lot of lactic acid, which of course, concerned me about off flavors...
...
RO water doesn't have enough alkalinity to shift the pH during sparging, so no need to acidify RO sparge water. The concern is when sparging with water having significant alkalinity.

Brew on :mug:
 
Here's the basics on mash water to sparge water volumes for maximizing efficiency. The desired ratios are different depending on whether you are fly sparging or batch sparging. As said early on above, ignore the water volume ratios that the recipe specifies.

When Fly Sparging: Use only as much mash water as you need to get the thickest mash you are comfortable with (able to easily stir at dough in, or recirculate, if your system requires it.) Use the balance of the water needed to reach your target pre-boil volume for fly sparging.

Can you expand on this a bit?

I have been operating under the reasoning that a thicker mash results in more sparge water which results in the end runnings being lower gravity and potentially extracting unwanted compounds. Is that not the case?


So if I mash the same grain bill twice:

Mash 1 is 3 gallons mash water and 5 gallons sparge water

Mash 2 is 5 gallons mash water and 3 gallons sparge water

Mash 1 will have a lower gravity on the final runnings assuming all other parameters are the same, correct?
 
@RickyBeers
I don't use RO water but I'm adding less than a ml to 16 litres of water to get the pH to 6.

Looks like I should be aiming a lower pH than that from the above info.
I have improved my mash efficiency with a " wetter " mash, finer crush and less sparge, but originally the sparge water was pouring through far too quickly.

I found this chart helpful and the advice of @doug293cz on various threads.
Mash Sparge Liquor.JPG


I don't have the chart in old money I'm afraid.

Also if you want to lose yourself for several hours Braukaiser.com will fill your head up quite nicely.
 
Can you expand on this a bit?

I have been operating under the reasoning that a thicker mash results in more sparge water which results in the end runnings being lower gravity and potentially extracting unwanted compounds. Is that not the case?


So if I mash the same grain bill twice:

Mash 1 is 3 gallons mash water and 5 gallons sparge water

Mash 2 is 5 gallons mash water and 3 gallons sparge water

Mash 1 will have a lower gravity on the final runnings assuming all other parameters are the same, correct?
This is easy to test out using my mash and sparge simulator (that you can download from here.)

Let's use a session beer recipe as an example, as it will be worst case: 6 lb grain bill with a weighted average potential of 1.037 (dry basis), 100% conversion efficiency, 0.12 gal/lb grain absorption, and 0 gal undrainable MLT volume.
Code:
Mash   Sparge   Sparge   Thickness  Pre-Boil
 gal    gal       SG       qt/lb       SG

  2      6      1.0138      1.3      1.0273
  3      5      1.0113      2.0      1.0277
  4      4      1.0104      2.7      1.0278
 4.36   3.64    1.0103      2.9      1.0278  (Equal run-off case)
  5      3      1.0105      3.3      1.0278
  6      2      1.0117      4.0      1.0276
So your assumption that a higher sparge water to strike water ratio gives you lower sparge wort SG is false. The minimum sparge wort SG occurs for the case of equal volume initial and sparge run-offs.

We can also see that for low OG beers, it is possible to get into the sparge SG range that can be problematic. If we raise the grain bill to 8 lb, and keep the pre-boil volume the same, things get better:
Code:
Mash   Sparge   Sparge   Thickness  Pre-Boil
 gal    gal       SG       qt/lb       SG

 4.60   3.64    1.0158      2.3      1.0360  (Equal run-off case)

Brew on :mug:
 
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This is easy to test out using my mash and sparge simulator (that you can download from here.)

Let's use a session beer recipe as an example, as it will be worst case: 6 lb grain bill with a weighted average potential of 1.037 (dry basis), 100% conversion efficiency, 0.12 gal/lb grain absorption, and 0 gal undrainable MLT volume.
Code:
Mash   Sparge   Sparge   Thickness  Pre-Boil
 gal    gal       SG       qt/lb       SG

  2      6      1.0138      1.3      1.0273
  3      5      1.0113      2.0      1.0277
  4      4      1.0104      2.7      1.0278
 4.36   3.64    1.0103      2.9      1.0278  (Equal run-off case)
  5      3      1.0105      3.3      1.0278
  6      2      1.0117      4.0      1.0276
So your assumption that a higher sparge water to strike water ratio gives you lower sparge wort SG is false. The minimum sparge wort SG occurs for the case of equal volume initial and sparge run-offs.

We can also see that for low OG beers, it is possible to get into the sparge SG range that can be problematic. If we raise the grain bill to 8 lb, and keep the pre-boil volume the same, things get better:
Code:
Mash   Sparge   Sparge   Thickness  Pre-Boil
 gal    gal       SG       qt/lb       SG

 4.60   3.64    1.0158      2.3      1.0360  (Equal run-off case)

Brew on :mug:

Thanks! Have you had a chance to verify your simulator? Knowing you, I'm sure you have but thought I should ask.

So I just need to be more diligent about acidifying my sparge water more and not worrying about the ratio too much other than as needed to control proteolysis and fermentability.
 
Thanks! Have you had a chance to verify your simulator? Knowing you, I'm sure you have but thought I should ask.

So I just need to be more diligent about acidifying my sparge water more and not worrying about the ratio too much other than as needed to control proteolysis and fermentability.
Comment on accuracy of my mash simulator

Brew on :mug:
 
@RickyBeers
I don't use RO water but I'm adding less than a ml to 16 litres of water to get the pH to 6.

I was realizing only tonight that a volume amount like this might be the case. And if one was to do a 3 gallon sized beer that used only a gallon of filtered tap water to sparge, the amount of 10% phosphoric acid needed is on the order of... a single drop?

I'm looking at Brewer's Friend and if I'm entering things right... I'm seeing close to 2ml there, for a gallon. I suppose it's highly dependent on your source water?

I'm not trying to say you're wrong - for the record! Just trying to learn and see if what I've been doing is wrong.
 
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I usually set mine to 2 qt/lb. You take a minor hit on efficiency but that should always be a lower priority than flavor/quality

What makes you think you'll get an efficiency hit if you mash thinner? The traditional German ratio is 2.0-3.0 qt/lbs.

Since moving to my AIO, I've been mashing thinner and getting excellent efficiency, three times over 80% with a .35 grain crush.
 
@RickyBeers
I don't use RO water but I'm adding less than a ml to 16 litres of water to get the pH to 6.

Looks like I should be aiming a lower pH than that from the above info.
I have improved my mash efficiency with a " wetter " mash, finer crush and less sparge, but originally the sparge water was pouring through far too quickly.

I found this chart helpful and the advice of @doug293cz on various threads.
View attachment 751073

I don't have the chart in old money I'm afraid.

Also if you want to lose yourself for several hours Braukaiser.com will fill your head up quite nicely.

I’m sure I should be able to understand this chart. But I don’t. Can you dumb this down for me?

And yes I will check out that website. Thank you
 
American Light Lager per the style is a fairly low ABV beer. The more sparge water than what you think normal seems to ensure you won't wind up with a high OG. More OG will mean higher ABV which might not be a light lager anymore.

Just a uneducated guess. But that's what I'm going with till someone comes up with something better.
Overall water volumes relation with grainbill is what is indicative of og, not mash volume by itself. If the recipe calls for less mash water than sparge, that typically means it’s a small grain bill and only need that much water for fill conversion and efficiency but you system has a certain preset amount of volume loss. So the sparge will have a larger volume to account for the losses
 
@TracerBullet
I've just checked on the brewers friend advanced water calculator for an american stout I made
21 litres mash and 14 litres sparge, 7.1 kg grain, my tap water pH 7.4 and to acidify sparge water ( no salts added ) to pH 6 required 0.44 ml Lactic acid.

Checking what it would be for a sparge water pH of 5.2 required 0.66ml. If phosphoric 10% used then it would need 6.5ml.

So for a 3 gallon batch with 1 gallon sparge that does seem the right ballpark

A few hydrogen ions do go a long way in plain water. Chuck in some grains and then there is buffering which complicates things.
 
@RickyBeers
L is Liquor ( water ) in kg
G is grist in kg
Its as a ratio L:G (Liquor (water) to Grist) and that figure reads across the x bottom axis.
Y axis is the maximum extraction for that ratio.
But you must take into account the loss of water into the grist as well as that affects volume.

So for the real world 15 litre water 5 kg grain gives L:G of 3
So would get 11 litre of wort run off calculated by 15 - ( 5x0.8) and that would be OG of 1.08

Has that helped or confused more?
 
@RickyBeers
L is Liquor ( water ) in kg
G is grist in kg
Its as a ratio L:G (Liquor (water) to Grist) and that figure reads across the x bottom axis.
Y axis is the maximum extraction for that ratio.
But you must take into account the loss of water into the grist as well as that affects volume.

So for the real world 15 litre water 5 kg grain gives L:G of 3
So would get 11 litre of wort run off calculated by 15 - ( 5x0.8) and that would be OG of 1.08

Has that helped or confused more?
Helped considerably, thank you for the explanation.
Looking forward to using these guidelines moving forward.
Also thank you doug
 
I'll just mention again there is no rule that you have to use all your recipe water for either mash or sparge. There is nothing wrong with adding some of the total water directly to the boil kettle if that is what it takes to avoid over sparging.

This is probably not an issue for a 4-5% ABV beer but I've used it before working on beers in the 3% range.
 
What makes you think you'll get an efficiency hit if you mash thinner? The traditional German ratio is 2.0-3.0 qt/lbs.

Since moving to my AIO, I've been mashing thinner and getting excellent efficiency, three times over 80% with a .35 grain crush.

Well I was thinking Because a thinner mash means less sparge water and therefore a shorter sparge and a less efficient lauter, but as Doug has shown that's not correct, so disregard
 

Doug I just had a thought...

your simulation is looking at batch sparges, so the results of your sparge gravity reflect the average gravity of the sparge runnings of a fly sparge (effectively).

but a fly sparging generates a vertical sugar gradient through the grain bed. So visualizing the curve of SG reaching the boil kettle if this were plotted: SG that reaches the boil kettle at the beginning of the sparge is much higher than the average value, and the SG near the end of a fly sparge must be far below the average value

If that's the case, then at least the upper portions of the grain bed would be subjected to a lower than desired SG

Following this out, as a thought experiment, consider a brewer conducting a 60 minute fly sparge with a high sparge water to mash water ratio:

The sparge water near end of the sparge starts at the top of the grain bed with a very low SG approaching 1.000.

Because the grains below have already been rinsed for 50 mins by a relatively high volume of water the gravity of this sparge water may not rise above 1.010 until it's passed through a significant portion of the grain bed and extracted polyphenols which it then carries through the remaining portion of the grain bed and into the boil kettle.

If the brewer reduces the total volume of sparge water but keeps the fly sparge time the same, then there would be more sugar remaining in the grain at the 50 minute mark, OR the "line" within the grain bed where the SG of the sparge rises above 1.010 sits higher up and thereby reduces the amount of grain that the low SG sparge water passes through
 
I usually mash in with 1.5 quarts per pound. Your recipe has 7.85 lbs of grain. So 1.5 x 7.85 = 11.77 quarts / 4 = 2.94 you could mash in with 3 gallons.

We lose some water to absorbtion, in my system it works out to about a pint per pound. Plus you have to account for any “dead space” in your mash tun, water that gets left behind. So 7.85 x 1.5 = 11.77 minus roughly 3.75 = In my system I would be left with just about 2 gallons after absorbtion and dead space losses.

Then you have to know your boil time and evaporation rate. In my system I lose about 1/2 gallon per hour to evaporation. So for 5.5 gallons you want to collect 6 gallons to boil down to a final 5.5 with a 60 min boil. If you’re starting with 2 gallons then you need to add 4 more. So it does look like slightly more sparge water than mash water but that will vary by your grain bill and batch size, its not a constant.
 
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