Interesting! So per this, I should do as much mash water as possible, but then do 3 full batch sparges?

Sorry to be slow on the response to this question.

It comes down to how much water you want to have to boil off. Figuring out how much water to use works backwards from your target volume to the fermenter.

- Target Post-Boil Volume = Target Fermenter Volume + BK Trub and Plumbing Losses
- Target Pre-Boil Volume = Target Post-Boil Volume + Boil-Off Volume
- Total Brewing Water Volume = Target Pre-Boil Volume + Grain Absorption + MLT Undrainable Volume

You can increase efficiency by increasing your total brewing water, but that forces you to boil off more volume to reach your target post-boil volume.

So, once you know what total brewing water volume you need (can tolerate), you have to decide how many sparge steps you are willing to do, and divide up your total brewing water between strike and sparge(s). You maximize efficiency by having all run-off volumes (initial mash and all sparges) be equal. Being exactly equal is not necessary, as you get an insignificant loss in efficiency as long as the volumes aren't wildly different.

As long as the mash doesn't get too thick to be processed, the math for calculating volumes looks like this:

Strike Volume = Grain Absorption + MLT Undrainable Volume + Pre-Boil Volume / (N + 1)

Sparge Volume = Pre-Boil Volume / (N + 1)

Where "N" is the number of sparge steps you intend to do (if N = 0, then you don't bother with the second formula above.)

If the above formulas result in a mash that is too thick for your system, then you need to modify the calculations too keep your mash thin enough. This is more likely to happen with large grain bills (high OG beers.) First you determine the minimum mash thickness you want (in qt/lb) and then:

Minimum Strike Volume [gal] = (Grain Bill Wt * qt/lb) / 4

Actual Strike Volume = max( Minimum Strike Volume, Grain Absorption + MLT Undrainable Volume + Pre-Boil Volume / (N + 1))

Sparge Volume [each step] = (Total Brewing Water Volume - Strike Volume) / N

So for maximum efficiency, you would do an infinite number of small sparges, and then the three formulas above become two:

Strike Volume = (Grain Bill Wt * qt/lb) / 4

Total Sparge Volume = Total Brewing Water Volume - Strike Volume

Sparging is done by adding a tiny amount of sparge water, then draining off an equally tiny amount of wort, repeating until you have used all of your sparge water, and finally draining any remaining wort. This is a fly sparge or continuous sparge.

Brewers go to batch sparging because it is less work and faster then fly sparging, and they accept that they will have slightly less than maximum efficiency. You have to decide what the proper trade-off is for time/effort vs. marginal increases in efficiency.

The chart doesn't tell you how you should sparge, it tells you what the effect of different choices are. You still have to make the choice in the paragraph above.

Brew on