Maths of Double vs. Single Batch Sparge Efficiency

I have an odd urge to contribute to everyone's theoretical understanding of brewing. We can all improve our methods by living by the motto "There are no black-boxes," meaning we shouldn't just go through the motions without understanding what we're doing or why. That leads to silly superstitions and flat-out incorrect methodology at times.

I've noticed that a good number of you have experimentally observed the efficiency difference between single and double sparge methods when brewing. Generally, you will find that double sparging leads to greater efficiency. As a chemist with a strong analytical background I often take the mathematics of this phenomenon for granted. Some of you may be interested in seeing why exactly a greater number of small-volume batches result in greater extraction.

Before linking to the math, this is the basic situation. Regardless of whether you are rinsing out a glass or sparging grain, two small rinses of say 5 mL (arbitrary volume) will always extract more than a single rinse of 10 mL even though you used the same total volume or rinse water. If you need proof, check out this relatively well written chemistry lab I found online:

http://www.ic.sunysb.edu/Class/che133/techniques/rinsing/rinsing.html

If someone needs simplification or wants to see this math applied to brewing directly, let me know. If I don't check back, I know there's someone else lurking here that could step up!

Happy brewing, friends.

Yes but, haha there are always exceptions and clarifications. A single batch sparge is really two rinses of the grain, and a double batch sparge is three rinses, so in theory, what is the gain doing a double vs single batch sparge for an average batch? I have heard 2 maybe 3 points?

I have also heard wort quality can diminish with subsequent sparges? Rumor or myth idk?

Some think that time is expensive and grain is cheap. Therefore the double sparge is not worth it?

Others chase efficiency?

Personal preference I guess... Cheers!

It's been hashed out so many times. It's probably best not to use this thread as another reason to debate chasing efficient vs. not. The way I read it was, we all know that increasing the discrete sparges does boost efficiency in most cases and the logic/math agrees with it. Most people don't see enough benefit to bother. Many people intentionally keep efficiency relatively low on purpose.

It's probably best not to use this thread as another reason to debate chasing efficient vs. not.

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Agreed. I'm not advocating for greater numbers of sparge steps. As a matter of fact I typically single sparge. Understanding the math can only help us, though, and I couldn't find any quantitative posts on this topic.

I have also heard wort quality can diminish with subsequent sparges?

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Absolutely true. Tannin extraction increases. As with nearly all aspects of brewing, it's a give and take situation. You can avoid this by keeping your sparge water temperature on the lower end of the usual range. A reasonable solution may be to initially mash out with high temp in the "zeroith" sparge prior to taking the first runnings, and then follow up with another sparge or two of lower temperature water.

With all this said I'll still likely single sparge (K.I.S.S.), but this thread was a gedankenexperimente. Keeps us sharp.

rdshup01 said:

With all this said I'll still likely single sparge (K.I.S.S.), but this thread was a gedankenexperimente.

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Gesundheit.

Oops, just realized I probably should have placed this under brew science. As you can see from my low post count, I'm relatively uninitiated. Sorry, guys.