Very interesting that you believe the effect of calcium on lowering the pH of the mash to be a lot less than previously thought by Kolbach. There are a good number of calculators out there that still use his magic 3.5 divisor.I've mentioned this multiple times already of late, but if our interpretation of Kolbach as to the influence of calcium and magnesium has been grossly incorrect and overstated then our interpretation of RA (Residual Alkalinity) is also grossly incorrect. And if (as per Barth and Zaman) calcium's impact upon downward pH shift within the mash is vastly different for each malt within a grist, then RA becomes essentially a contrived figment of our imagination.
Kolbach stated this:
mEq/L RA = mEq/L Alkalinity - [(mEq/L Ca)/3.5 + (mEq/L Mg)/7]
Barth and Zaman only looked at calcium, but they looked at its impact during the mash as opposed to knockout, and whereas for the case of knockout Kolbach established '3.5' as the divisor for calcium (meaning that for every 3.5 mEq's of calcium 1 mEq of Alkalinity is consumed) Barth and Zaman found that for their specific lots of the three malts they tested the divisor was as follows within the mash:
Pilsner malt divisor = 14.8 (vs. 3.5)
Pale Ale malt divisor = 7.2 (vs. 3.5)
Munich malt divisor = 12.2 (vs. 3.5)
Where I find potential flaw in Barth and Zaman is that they measured only 5 minutes into the mash whereby to establish these divisors. I think they should have tested at 30, 45, and 60 minutes into the mash. And I suspect the divisors would have diminished measurably thereby, albeit not all the way to 3.5. I suspect that they did not allow for sufficient time for the added calcium ions within the mash water to permeate into the confines of the crushed malts whereby to release H+ ions.
Could you say what you think is the best way to deal with pH control in the mash? Do you have a preferred way of dealing with alkalinity? How about pre-boiling the water to remove carbonates or adding acids like AMS or lactic...or maybe just adjusting the grain bill? Or maybe using distilled water and adding the minerals that are needed, if any?