So I was goofing around today with acid malt calculations in my spreadsheet and was trying to reconcile Weyermann recommendations, Kai's numbers and the values given at a strength setting of 1 in BW (said to coincide roughly with Weyermann's 1%/-0.1 pH). Here is what I found:
After inputting my DI pH values for my Base blend and Vienna malt, and calculating acidity for the CaraHell, as well as subtracting the pH drop for Ca and the Antioxin SBT, I was at 5.75 for mash pH.
With the strength multiplier set to 1 (stock BW) and 5% acid malt, pH dropped to 5.42.
I wrote a quick equation for Kai's numbers:
((Acid Malt (g)/22.7 (g))/(Strike Volume (gal)/1 (gal)))*(-122 (HCO3 drop))
I could then compare Kai's numbers to the pH while manipulating the strength multiplier. While still at 5% acid malt, and a strength setting of 1.3, the pH drop predicted by my sheet matched Kai's numbers at 5.322.
I then manipulated the strength setting until I could see that 1% acid malt additions were providing a pH drop of 0.1. At 5% acid malt, with a strength setting of 1.5, my spreadsheet matched Weyermann's numbers and provided a prediction of 5.26.