Strikewater volume?

[Closet Fermenter]

I have been wondering about strikewater volume. I have brewed off/on for 30+ years, but more seriously and regularly in the past half dozen when I switched to all-grain. I have followed a guide I found somewhere that suggests using 1.5 quarts water/ lb grain for mashing. Typically, I need a greater amount of sparge water than strikewater if I follow this guide.
My question is this; would it not induce a higher sugar extraction with a greater volume of strikewater? It’s been decades since I took any chemistry/physics, but I recall something about movement from higher concentrations to lower and the greater the flow with increased gradient between the two. My thoughts are with a larger volume of strikewater, a steeper gradient is maintained longer that would promote higher sugar extraction.
Also, I am thinking that a sparge isn’t going to get you anything that wasn’t already extracted in the mash.
I confess that I have been going a little higher on the strikewater, and less on the sparge and have been getting higher than expected OG.

Is there something I am missing or neglecting that that would cause you to recommend that I reconsider my thoughts here?

Thanks!

 

[lumpher]

I usually use more mash water than sparge water, but I don't do calculations. Bring on the mathematicians to prove us wrong...

 

[doug293cz]

I have been wondering about strikewater volume. I have brewed off/on for 30+ years, but more seriously and regularly in the past half dozen when I switched to all-grain. I have followed a guide I found somewhere that suggests using 1.5 quarts water/ lb grain for mashing. Typically, I need a greater amount of sparge water than strikewater if I follow this guide.
My question is this; would it not induce a higher sugar extraction with a greater volume of strikewater? It’s been decades since I took any chemistry/physics, but I recall something about movement from higher concentrations to lower and the greater the flow with increased gradient between the two. My thoughts are with a larger volume of strikewater, a steeper gradient is maintained longer that would promote higher sugar extraction.
Also, I am thinking that a sparge isn’t going to get you anything that wasn’t already extracted in the mash.
I confess that I have been going a little higher on the strikewater, and less on the sparge and have been getting higher than expected OG.

Is there something I am missing or neglecting that that would cause you to reconsider my thoughts here?

Thanks!

There are two efficiencies you need to consider here: conversion efficiency which measures how much of the potential extract (sugar, etc.) you actually create in the mash, and lauter efficiency which measures how much of the extract actually created in the mash makes it into your boil kettle. Mash efficiency equals conversion efficiency times lauter efficiency, and conversion efficiency and lauter efficiency are pretty much independent of each other (affected by different factors.)

Strike water to grain ratio does not directly affect conversion efficiency, although it can affect the rate of conversion, with thinner mashes converting faster than thicker mashes (all else being equal.) So, it might take a bit more mash time to get the same conversion efficiency with a thick mash vs. a thin mash. But, you can measure the progress of conversion by monitoring the SG of the wort in the mash, and not stopping the mash until the SG becomes stable with time (not increasing anymore.)

Lauter efficiency on the other hand is hugely affected by strike water to sparge water volume ratio, and the details of how it is affected depend on whether you are batch sparging or fly sparging. For batch sparging, the maximum lauter efficiency is obtained when the initial mash run-off, and all sparge run-offs have equal volume. The change of efficiency with volume ratio is however pretty insensitive to the precise ratio if you are in the 60:40 to 40:60 range.

For fly sparging on the other hand, lauter efficiency is maximized when you use the minimum amount of strike water that will work with your system, and then sparging with the balance of the brewing water.

For either sparge process, you want to insure that the wort in the mash is well homogenized prior to the start of each run-off. If you don't do this, then the initial run-off wort will be lower SG than the wort retained in the grain prior to sparging, and lauter efficiency will suffer because of that.

Brew on

 

[doug293cz]

I usually use more mash water than sparge water, but I don't do calculations. Bring on the mathematicians to prove us wrong...

A detailed, science and math based reply takes longer to type.

To get equal run-off volumes with single batch sparging, strike water volume needs to be higher than sparge water volume because of grain absorption. For fly sparging, you want to use more sparge water than strike water, if that works in your system.

Brew on

 

[uweschmitt]

You can also find discussions about mash thickness in this thread.

I mash and boil on my kitchen stove and limited space and pot sizes influence the amount of water I'm using for mashing and sparging. Lighter beers with less malt allow me to vary water amounts but I did not really note any differences in the final beer. For small batches of l table beers you might want to try no-sparging, which is less work and apperently has some benefits, e.g. reduced extraction of tannins, see also this discussion.

 

[SFC Rudy]

I use John Palmers math in an excel spreadsheet and my sweet spot is using 40% of my boil volume as batch sparge water. If my boil volume is 6 gallons I use 2.4 gallons of sparge water. For strike water take your grain bill and multiply it by your grain absorption, 1/2 qt/lb (.125 gallon) then add 3.6, that is how much strike water you need.

Example: You want a boil volume of 6 gallons. You have 10 lbs of grain. 10*.125=1.25 gallons of water that will be absorbed by the grain. Add 3.6 and you get 4.85 gallons of strike water. Then you sparge with 2.4 gallons and end up with 6 gallons of wort. The 40%, or 2.4 gallons is my number, you can change it to fit your system.

 

[day_trippr]

Answer 1: the minimum dead space under an FB that allows full drain port exposure is optimal. Increasing that volume is suboptimal.

Answer 2: "Yes". Your strike volume should be pounds of grain times your preferred water to grain ratio plus the dead space volume...

Cheers!

 

[doug293cz]

I've upgraded my old coolbox/copper tube manifold mash tun to a thermo-pot with a false bottom and had a couple of questions. The drain is in the base of the thermopot, not the sidewall. The false bottom is a circle of stainless steel mesh, with some bolts that create little legs to elevate it off the bottom. This creates around 1" or 3cm of void beneath it, above the base of the pot and drain. Question 1: Is there an ideal depth to that void? The overall diameter of thermopot must be around 45cm so the grain bed is spread to a thinner depth over a wider area than in my old small rectangular coolbox so not sure how this will change the mash efficiency... time will tell. Question 2: As it stands, that void creates quite a bit of dead space beneath the mesh, and therefore beneath the grain bed. With my coolbox mashtun, when calculating my volume of strike water I had no dead space (aside from the negligible volume taken up by the copper tube manifold). I would just calculate my mash volumes on the general ratio of 1.5lts per kilo of grain (give or take). With this false-bottom tun, I havent measured that dead space beneath the bottom, but it must a good few litres of water beneath it, meaning when I come to mash in, that liquid isn't "available" and I guess would lead to a very stiff mash above the false bottom. Therefore - do I just work out that volume and increase my mash liquid volume accordingly?

Short answer: yes, you need to add the volume under the false bottom to your minimum acceptable strike volume for mash thickness to get your useful strike volume.

Based on your dimensions, I get your "dead" volume under the FB as ~4.8 L.

1.5 L/kg (0.644 qt/lb) is an extremely thick (and stiff) mash to begin with. Most brewers use at least 2.6 L/kg (1.25 qt/lb) as their maximum acceptable mash thickness (minimum strike water to grain ratio.)

The most efficient strike water volume depends on whether you are doing batch or fly sparging. If you are batch sparging, you want your strike water to be equal to your expected grain absorption plus 1/2 of your target pre-boil volume, and your sparge volume to be 1/2 your target pre-boil volume (for single sparge step.) If fly sparging, you want to use the minimum strike volume that gives you a workable mash thickness (and all grain covered by water during the mash) for best efficiency. Which type of sparging are you doing?

Brew on

 

[kurds_2408]

Short answer: yes, you need to add the volume under the false bottom to your minimum acceptable strike volume for mash thickness to get your useful strike volume.

Based on your dimensions, I get your "dead" volume under the FB as ~4.8 L.

1.5 L/kg (0.644 qt/lb) is an extremely thick (and stiff) mash to begin with. Most brewers use at least 2.6 L/kg (1.25 qt/lb) as their maximum acceptable mash thickness (minimum strike water to grain ratio.)

The most efficient strike water volume depends on whether you are doing batch or fly sparging. If you are batch sparging, you want your strike water to be equal to your expected grain absorption plus 1/2 of your target pre-boil volume, and your sparge volume to be 1/2 your target pre-boil volume (for single sparge step.) If fly sparging, you want to use the minimum strike volume that gives you a workable mash thickness (and all grain covered by water during the mash) for best efficiency. Which type of sparging are you doing?

Brew on

I know this was for someone else but wanted your knowledge for my setup And ratio I should use. I do a hybrid BIAB in a cooler method. For a sparge I just lift the bag with a hoist and poor 170F over it with a pitcher. Fly sparge adjacent I guess. I’ve played with it some but haven’t settled how much water is best yet. Usually do more mash water than sparge water but sounds like thats wrong from this thread? Any help is appreciated.

 

[doug293cz]

I know this was for someone else but wanted your knowledge for my setup And ratio I should use. I do a hybrid BIAB in a cooler method. For a sparge I just lift the bag with a hoist and poor 170F over it with a pitcher. Fly sparge adjacent I guess. I’ve played with it some but haven’t settled how much water is best yet. Usually do more mash water than sparge water but sounds like thats wrong from this thread? Any help is appreciated.

A pour over sparge, while similar to a fly sparge, is much more variable and difficult to get consistent results with. You would probably be better off switching to a dunk batch sparge, as it will be much more consistent and predictable.

To do the dunk sparge use the following steps:

1. At the end of the mash, stir the mash well to make sure the wort is well homogenized.
2. Lift and drain the bag completely.
3. (Optional) Squeeze the bag. It's more effective to squeeze the bag here vs. after the sparge.
4. Move the wort from your cooler to your boil kettle.
5. Add your sparge water to the cooler.
6. Lower the bag into the sparge water.
7. Open the bag and stir aggressively to homogenize the sparge water with the residual wort.
8. Lift and drain the bag completely.
9. (Optional) Squeeze the bag.
10. Move the sparged wort from your cooler to your BK.
11. Proceed to boil.

It doesn't really matter if your sparge water is hot or cold, although using hot water will reduce your time to achieve boil temp.

A simple rule of thumb, that will get you close enough to equal run-off volumes such that you won't be able to measure any reduction in lauter efficiency, is to use 60% of your total brewing water for strike, and the remaining 40% to sparge.

Brew on

 

[kurds_2408]

A pour over sparge, while similar to a fly sparge, is much more variable and difficult to get consistent results with. You would probably be better off switching to a dunk batch sparge, as it will be much more consistent and predictable.

To do the dunk sparge use the following steps:

1. At the end of the mash, stir the mash well to make sure the wort is well homogenized.
2. Lift and drain the bag completely.
3. (Optional) Squeeze the bag. It's more effective to squeeze the bag here vs. after the sparge.
4. Move the wort from your cooler to your boil kettle.
5. Add your sparge water to the cooler.
6. Lower the bag into the sparge water.
7. Open the bag and stir aggressively to homogenize the sparge water with the residual wort.
8. Lift and drain the bag completely.
9. (Optional) Squeeze the bag.
10. Move the sparged wort from your cooler to your BK.
11. Proceed to boil.

It doesn't really matter if your sparge water is hot or cold, although using hot water will reduce your time to achieve boil temp.

A simple rule of thumb, that will get you close enough to equal run-off volumes such that you won't be able to measure any reduction in lauter efficiency, is to use 60% of your total brewing water for strike, and the remaining 40% to sparge.

Brew on

Ok thank you. I’ll give that a try on my next brew. Been hitting my numbers but would like to bump up the efficiency some.

 

[tracer bullet]

You can also use the boil kettle for sparging:

Add the # of sparge gallons into the boil kettle ahead of time (bonus if your kettle has markings and you trust them or make your own)
Sparge water can be heated easily this way as well, but doesn't have to be
After the typical mashing up to this point, lift the grains out of the cooler and squeeze the bag over the cooler
Move the bag of grains to the boil kettle (w/ the sparge water) and place them in it
Massage the bag a bit to mix the grains and sparge water, etc.
Lift the bag and squeeze it again, your boil kettle now has what you sparged
Move the contents of the cooler into the boil kettle as well

I have a rather tall false bottom and I think I get a little bit more out of the process this way.

If you run electric or all-in-one never mind either of these variations

 

[kurds_2408]

A pour over sparge, while similar to a fly sparge, is much more variable and difficult to get consistent results with. You would probably be better off switching to a dunk batch sparge, as it will be much more consistent and predictable.

To do the dunk sparge use the following steps:

1. At the end of the mash, stir the mash well to make sure the wort is well homogenized.
2. Lift and drain the bag completely.
3. (Optional) Squeeze the bag. It's more effective to squeeze the bag here vs. after the sparge.
4. Move the wort from your cooler to your boil kettle.
5. Add your sparge water to the cooler.
6. Lower the bag into the sparge water.
7. Open the bag and stir aggressively to homogenize the sparge water with the residual wort.
8. Lift and drain the bag completely.
9. (Optional) Squeeze the bag.
10. Move the sparged wort from your cooler to your BK.
11. Proceed to boil.

It doesn't really matter if your sparge water is hot or cold, although using hot water will reduce your time to achieve boil temp.

A simple rule of thumb, that will get you close enough to equal run-off volumes such that you won't be able to measure any reduction in lauter efficiency, is to use 60% of your total brewing water for strike, and the remaining 40% to sparge.

Brew on

I had another question for you. I am planning to do this method for my next brew. I’m trying to set up BrewFather to calculate my water volumes and temps. I plan to squeeze the bag after both mash and sparge. Should I do standard absorption rate for mash (.125gal/lb) and 0 absorption for sparge? I was doing “default” before with my poor over but don’t know what that default was.

 

[doug293cz]

I had another question for you. I am planning to do this method for my next brew. I’m trying to set up BrewFather to calculate my water volumes and temps. I plan to squeeze the bag after both mash and sparge. Should I do standard absorption rate for mash (.125gal/lb) and 0 absorption for sparge? I was doing “default” before with my poor over but don’t know what that default was.

An unsqueezed BIAB bag has an absorption rate of about 0.08 gal/lb to 0.10 gal/lb (if drained for 10+ minutes, longer generally equates to lower.) Normally, no additional water volume is lost during the sparge step, as the grain is already holding its adsorbed water capacity. This is true for both BIAB, and traditional MLTs. However, if you squeeze the bag on initial draining, but not after sparging, you will lose some of the sparge water volume. I believe most brewing software assumes no loss of sparge water volume to grain absorption.

Brew on

 

[tracer bullet]

0.08 gal/lb to 0.10 gal/lb

Not arguing these numbers but for another data point if I squeeze the bejeezers out of a bag I'm more like .12 gallons per pound, and if I'm a tiny bit lazy or making an Imperial (more grain, harder to squeeze) it's closer to .16 gallons per pound. These numbers work out about perfectly for me.

 

[doug293cz]

Not arguing these numbers but for another data point if I squeeze the bejeezers out of a bag I'm more like .12 gallons per pound, and if I'm a tiny bit lazy or making an Imperial (more grain, harder to squeeze) it's closer to .16 gallons per pound. These numbers work out about perfectly for me.

Not sure what you are doing, but I have never had grain absorption rates that high when doing BIAB (nor heard of anyone else that has.)

Brew on

 

[tracer bullet]

Yep, math error on my part! I do things in quarts, and screwed my math up in my head wondering if I got the same #'s.

On 2nd though, doing the match correctly this time, I'm 100% with you on .08 gallons per pound if I squeeze, 0.10 if it's a big bill that's hard to squeeze as well.

Never mind!

 

[kurds_2408]

An unsqueezed BIAB bag has an absorption rate of about 0.08 gal/lb to 0.10 gal/lb (if drained for 10+ minutes, longer generally equates to lower.) Normally, no additional water volume is lost during the sparge step, as the grain is already holding its adsorbed water capacity. This is true for both BIAB, and traditional MLTs. However, if you squeeze the bag on initial draining, but not after sparging, you will lose some of the sparge water volume. I believe most brewing software assumes no loss of sparge water volume to grain absorption.

Brew on

Hey thanks so much man. You’ve been really helpful.

 

[Hoochin'Fool]

Yep, math error on my part! I do things in quarts, and screwed my math up in my head wondering if I got the same #'s.

On 2nd though, doing the match correctly this time, I'm 100% with you on .08 gallons per pound if I squeeze, 0.10 if it's a big bill that's hard to squeeze as well.

Never mind!

Am I the only one who's getting a lot lower grain absorption rate? My full-volume mash and then squeeze the hell out of the bag method seems to be a lot closer to 0.04 gal "lost" per lb of grain. Maybe even a little bit less, but my volume measurements aren't super precise. My pre-boil gravity is coming out spot on (now that I'm setting Brewers Friend brewhouse efficiency per Doug's "grain weight vs pre-boil volume" chart), but my volume is ending up higher than anticipated. Not saying it's a problem (hey, an extra hydrometer sample, and maybe an extra bottle or two), just wondering why the discrepancy in grain absorption is.

 

[tracer bullet]

Am I the only one who's getting a lot lower grain absorption rate? My full-volume mash and then squeeze the hell out of the bag method seems to be a lot closer to 0.04 gal "lost" per lb of grain. Maybe even a little bit less, but my volume measurements aren't super precise. My pre-boil gravity is coming out spot on (now that I'm setting Brewers Friend brewhouse efficiency per Doug's "grain weight vs pre-boil volume" chart), but my volume is ending up higher than anticipated. Not saying it's a problem (hey, an extra hydrometer sample, and maybe an extra bottle or two), just wondering why the discrepancy in grain absorption is.

I'm finding somethign similar as well, actually. I recently did a 2.5 gallon batch of beer with a little over 5 pounds of grain. I don't know I quite got to .04 but yeah it was a lot less than .08, I had about an extra 3/16 gallons beyond what I calculated.

Seems to really come down to how well / how hard you can squeeze which for me is directly proportional to the pounds of grain.

You aren't crazy. Well not about this anyhow haha.

 

[DBhomebrew]

I don't squeeze and get a remarkably consistent ~.0875

 

[doug293cz]

Am I the only one who's getting a lot lower grain absorption rate? My full-volume mash and then squeeze the hell out of the bag method seems to be a lot closer to 0.04 gal "lost" per lb of grain. Maybe even a little bit less, but my volume measurements aren't super precise. My pre-boil gravity is coming out spot on (now that I'm setting Brewers Friend brewhouse efficiency per Doug's "grain weight vs pre-boil volume" chart), but my volume is ending up higher than anticipated. Not saying it's a problem (hey, an extra hydrometer sample, and maybe an extra bottle or two), just wondering why the discrepancy in grain absorption is.

The grain absorption rate will be highly dependent on just how well you squeeze the wort out of the bag of grain. 0.04 is a believable value for a very aggressive and effective squeeze. The best thing you can do is make your volume measurements as accurate as possible, and keep track of your absorption rate. You want to get the rate as consistent as you can in order to have predictability of pre-boil volume. Once you know what your absorption rate is, put that into your brewing software, and that should help you hit your volume targets.

Brew on

 

[kurds_2408]

A pour over sparge, while similar to a fly sparge, is much more variable and difficult to get consistent results with. You would probably be better off switching to a dunk batch sparge, as it will be much more consistent and predictable.

To do the dunk sparge use the following steps:

1. At the end of the mash, stir the mash well to make sure the wort is well homogenized.
2. Lift and drain the bag completely.
3. (Optional) Squeeze the bag. It's more effective to squeeze the bag here vs. after the sparge.
4. Move the wort from your cooler to your boil kettle.
5. Add your sparge water to the cooler.
6. Lower the bag into the sparge water.
7. Open the bag and stir aggressively to homogenize the sparge water with the residual wort.
8. Lift and drain the bag completely.
9. (Optional) Squeeze the bag.
10. Move the sparged wort from your cooler to your BK.
11. Proceed to boil.

It doesn't really matter if your sparge water is hot or cold, although using hot water will reduce your time to achieve boil temp.

A simple rule of thumb, that will get you close enough to equal run-off volumes such that you won't be able to measure any reduction in lauter efficiency, is to use 60% of your total brewing water for strike, and the remaining 40% to sparge.

Brew on

Hey Doug I have another question for you after all this and some experiments. So in my equipment profile for this dunk spare should I just set and equation for the sparse water to always be 40% of my pre-boil volume? This obviously makes my sparge thicker with bigger beers and not as effective. Does it also change my mash thickness depending on grain weight? BrewFather also has an option to just set a grain/water ration and select batch sparge. I don't know what the math is for the batch sparge but it isn't exactly 60/40

 

[doug293cz]

Hey Doug I have another question for you after all this and some experiments. So in my equipment profile for this dunk spare should I just set and equation for the sparse water to always be 40% of my pre-boil volume? This obviously makes my sparge thicker with bigger beers and not as effective. Does it also change my mash thickness depending on grain weight? BrewFather also has an option to just set a grain/water ration and select batch sparge. I don't know what the math is for the batch sparge but it isn't exactly 60/40

Theoretically, you get the best lauter efficiency, when doing a single batch sparge, when the initial run-off volume and the sparge run-off volume are equal. But, the difference in lauter efficiency is less than 1% for ratios of 60:40 to 40:60. With the accuracy that is typical for homebrew measurements, efficiency calculations have an uncertainty of about +/- 4%, so you can't reliably detect a 1% difference. Here's a chart from Kai Troester (Braukaiser) that shows how lauter efficiency varies with run-off volume ratio:

As you can see, lauter efficiency decreases with increasing grain bill weight for a fixed batch size. This can be seen better if we normalize by dividing the grain bill weight by the pre-boil volume, which gives us a chart that is independent of batch size.

Because the grain absorption losses all show up in the initial run-off volume, you want to use more strike water than sparge water, for a batch sparge.

Here's a table made for 6.5 gal pre-boil volume and 0.08 gal/lb grain absorption rate, that shows the run-off volume ratios for various grain bill weights, using 60% of total water for strike, and 40% for sparge:

Grain Wt (lb)​	Initial Run-off Volume %​	Sparge Run-off Volume %​	Pre-Boil SG @ 100% Conv​	Mash Thickness (qt/lb)​
5.0​	57.5​	42.5​	1.0265​	3.31​
7.5​	56.3​	43.7​	1.0386​	2.27​
10.0​	55.1​	44.9​	1.0497​	1.75​
12.5​	53.8​	46.2​	1.06​	1.44​
15.0​	53.2​	46.8​	1.0699​	1.23​
17.5​	51.4​	48.6​	1.0779​	1.08​
20.0​	50.2​	49.8​	1.0858​	0.97​

You can see that with the 60:40 rule of thumb, the run-off volume ratios all stay within the 60:40 to 40:60 range. This table is for the relatively low grain absorption rate typical of BIAB. For a traditional MLT the absorption rate would be closer to 0.12 gal/lb and the table then looks like this:

Grain Wt (lb)​	Initial Run-off Volume %​	Sparge Run-off Volume %​	Pre-Boil SG @ 100% Conv​	Mash Thickness (qt/lb)​
5.0​	56.3​	43.7​	1.0261​	3.41​
7.5​	54.5​	45.5​	1.0375​	2.37​
10.0​	52.6​	47.4​	1.0478​	1.85​
12.5​	50.8​	49.2​	1.0569​	1.54​
15.0​	48.9​	51.1​	1.0651​	1.33​
17.5​	47.1​	52.9​	1.0725​	1.18​
20.0​	45.2​	54.8​	1.079​	1.07​

Again, the run-off volume ratios stay within the highest efficiency range. This shows the rule of thumb for 60% strike, 40% sparge works for a wide range of grain weights and grain absorption rates. Although if you typically get grain absorption rates of 0.08gal/lb, or less, you might want to change to 55% strike and 45% sparge to center things up in the "good" range a little bit better.

Note that for the larger grain bills, the mash thickness can get pretty stiff (less than 1.25 qt/lb), and in these cases, you might want to shift more of the total water to strike (so that you can stir the mash.)

Brew on

 

[kurds_2408]

Theoretically, you get the best lauter efficiency, when doing a single batch sparge, when the initial run-off volume and the sparge run-off volume are equal. But, the difference in lauter efficiency is less than 1% for ratios of 60:40 to 40:60. With the accuracy that is typical for homebrew measurements, efficiency calculations have an uncertainty of about +/- 4%, so you can't reliably detect a 1% difference. Here's a chart from Kai Troester (Braukaiser) that shows how lauter efficiency varies with run-off volume ratio:

View attachment 832483

As you can see, lauter efficiency decreases with increasing grain bill weight for a fixed batch size. This can be seen better if we normalize by dividing the grain bill weight by the pre-boil volume, which gives us a chart that is independent of batch size.

View attachment 832484

Because the grain absorption losses all show up in the initial run-off volume, you want to use more strike water than sparge water, for a batch sparge.

Here's a table made for 6.5 gal pre-boil volume and 0.08 gal/lb grain absorption rate, that shows the run-off volume ratios for various grain bill weights, using 60% of total water for strike, and 40% for sparge:

Grain Wt (lb)​	Initial Run-off Volume %​	Sparge Run-off Volume %​	Pre-Boil SG @ 100% Conv​	Mash Thickness (qt/lb)​
5.0​	57.5​	42.5​	1.0265​	3.31​
7.5​	56.3​	43.7​	1.0386​	2.27​
10.0​	55.1​	44.9​	1.0497​	1.75​
12.5​	53.8​	46.2​	1.06​	1.44​
15.0​	53.2​	46.8​	1.0699​	1.23​
17.5​	51.4​	48.6​	1.0779​	1.08​
20.0​	50.2​	49.8​	1.0858​	0.97​

You can see that with the 60:40 rule of thumb, the run-off volume ratios all stay within the 60:40 to 40:60 range. This table is for the relatively low grain absorption rate typical of BIAB. For a traditional MLT the absorption rate would be closer to 0.12 gal/lb and the table then looks like this:

Grain Wt (lb)​	Initial Run-off Volume %​	Sparge Run-off Volume %​	Pre-Boil SG @ 100% Conv​	Mash Thickness (qt/lb)​
5.0​	56.3​	43.7​	1.0261​	3.41​
7.5​	54.5​	45.5​	1.0375​	2.37​
10.0​	52.6​	47.4​	1.0478​	1.85​
12.5​	50.8​	49.2​	1.0569​	1.54​
15.0​	48.9​	51.1​	1.0651​	1.33​
17.5​	47.1​	52.9​	1.0725​	1.18​
20.0​	45.2​	54.8​	1.079​	1.07​

Again, the run-off volume ratios stay within the highest efficiency range. This shows the rule of thumb for 60% strike, 40% sparge works for a wide range of grain weights and grain absorption rates. Although if you typically get grain absorption rates of 0.08gal/lb, or less, you might want to change to 55% strike and 45% sparge to center things up in the "good" range a little bit better.

Note that for the larger grain bills, the mash thickness can get pretty stiff (less than 1.25 qt/lb), and in these cases, you might want to shift more of the total water to strike (so that you can stir the mash.)

Brew on

Oh wow. Thank you so much. Wasn't expecting that much info. Super helpful to see all that. I'm still dialing in this new setup. Trying to figure out my exact grain absorption and what my pre-boil needs to be to hit my batch size perfect but I'll be sure to stick in that range. Thanks.