Batch sparging variations and efficiency

[Lost]

So I've always done fly sparging but with 10 gal batches it just takes so long that I'm considering moving to batch sparging. That said, I have some questions regarding technique and efficiency. Yes, I read the sticky


I'm planning on a split sparge (drain, 1st sparge, 2nd sparge) but I'm wondering why the runnings must be equal. Why not add more on the first batch and less on the second? Intuitively I feel like that would result in better extraction..

There's some fancy forumula's at http://braukaiser.com/wiki/index.php?title=Batch_Sparging_Analysis that shows that for a single batch sparge the volume of the sparge should match the volume of the initial run-off/drain. So if you drain the kettle and get 7 gallons out then the batch sparge should be 7 gal also (for max efficiency) and the preboil volume would then be set at 14 gal. What this means, really, is that if max efficiency is the goal, pre-boil volume is a consequence of mash thickness because mash thickness (and grain absorbtion) determine the volume of the initial runnings and the sparge should match the volume of the initial runnings.

Importantly, the author of the above article then goes on to "assume" that equal run-off volumes result in max efficiency where *multiple* (e.g. 2 or 3) batch sparges are done. There's no justification or discussion of this and this assumption is then carried through the rest of the calculations on the page.

If the assumption is true, and I'm dubious, then the correct calculation would seem to be to work backward from preboil volume to determine the correct mash thickness. If you know your target preboil volume you divide that by 3, that number is the volume of each of the two batch sparges and, after adjusting upward for loss due to grain absorption it is also the strike water volume. From there the mash thickness ratio is simply the lbs divided by the strike volume.

I've got an excel spreadsheet where all this is calculated out. It's got 2 calculations - the first you enter the desired mash thickness ratio and it gives you preboil volume and sparge volumes as a result. The second calc you enter target preboil volume and it spits out your mash ratio and sparge volumes.

I'd post the spreadsheet but I don't know how. Perhaps one of you would be so kind.

Returning to the question, though, am I calculating sparge volumes correctly for a split sparge process? Can someone help me understand why the sparges and the initial run off volumes should be equal?

 

[Malticulous]

Equal runoffs are best. It dosen't have to be exact. You simply will get the most extract in to the water that way.

I just strike with half the boil volume plus the absorption and dead space (.5 qt/lb for my setup-simple enough to do in my head even after a few.) The single sparge is just half the boil volume. You would just use thirds of the boil volume for a double sparge. The second spage is only worth about 3%. I get ~85% BHE with the single sparge method.

 

[Lost]

I get that equal sized sparges that, apparently, also match the volume of the 1st runnings are supposed to maximize the sugar extract. I just don't see why that is.

It seems to me that the volume in the mash (and thus the 1st runnings) is irrelevant except that it would affect the amount of water that can be used for sparging. Thus, less strike water would be better up to the point that so little water is used that full conversion is not possible.

In the end, it's not a big deal, just more of a curiosity. I've got my mash volume calculations down and we'll see how it works on my next batch. If anyone wants to post the spreadsheet the offer still stands. It calculates mash volume, strike water temp, infusion volume (if you want to do an infusion), and mashout. The mashout calculator is for using a portion of the wort, boiling it, and adding it back in to mashout. In this way I should be able to keep more water for the batch sparge which should, hopefully, get me slightly higher efficiency.