pH during the sparge batch vs fly/continuous

Perhaps I've simply missed it somewhere, but I've never read anything describing why a batch sparger's pH won't generally change much (Denny Conn has said that he's measured it..though he lives in oregon and may have low mineral water) when they sparge, and thus there's not nearly as much concern about tannins with batch sparging. Yet, there seems to be with fly sparging (I say there seems to be, since I've always batch sparged.). Does anyone know the reason for this? Is it simply the prolonged contact time that's involved in fly sparging that causes the pH to rise more? I know the mash acts as a pretty decent buffer, do buffers become less effective over time?

My guess would be on sugar concentration levels which seem to buffer the solution. When you batch sparge your gravities remain higher while fly sparging slowly rinses the sugar away and around 1.010 you start worrying about pH issues.

Bensiff said:

My guess would be on sugar concentration levels which seem to buffer the solution. When you batch sparge your gravities remain higher while fly sparging slowly rinses the sugar away and around 1.010 you start worrying about pH issues.

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Hmm, that would make sense. I'm curious if AJ or Martin have a scientific explanation as to how the sugars buffer the pH (or someone else...I don't really care who answers it)?

With a batch sparge, the dangers of oversparging and higher final mash runnings pH are quite a bit lower than with fly sparging. The larger volume of buffers (and sugars) remaining in the grist for the second batch sparge make it much less possible to create those oversparge and high mash pH conditions. But this is not to say that it can't be done. Batch spargers should still properly acidify their sparge water to ensure that the mash pH remains relatively low and the overall wort pH is not too high.

Is it fair to say that I don't need to acidify my sparge water if I am using deionized/RO water for the sparge? I do all of my mineral additions to the mash water, and never do anything to my deionized sparge water. I batch sparge.

You'll be fine

Yes, there is no need to acidify RO or distilled water for sparging use. Also, since RO and distilled water have very low alkalinity, it would only take teeny amounts of acid to reduce the water's pH to desirable sparging pH. In any case, the need for acidification is quite low.