The A(pH) + B(pH) + C + D(pH) = 0 model is going to give you the best pH predictions provided that you feed it good data which really goes without saying. Simplified models in which the pH is computed as the average pHdi, the weighted average pHdi (best when weighted by a1 and mass; not quite as good if weighted by malt mass only) corrected by acid/base estimates of other mash components divided by estimated buffering capacity of the mash will give reasonable answers but not ones as good as those from the full model (A(pH) + B(pH) + C + D(pH) = 0). The extent of the sacrificed accuracy depends on how many of the simplifications/approximations are put into place in order to get the linearized result. Thus someone who wants to put together a spread sheet or calculator has a choice as to where between solving A(pH) + B(pH) + C + D(pH) = 0 iteratively for pH and pH ≈ ∑mi*pHdi/∑mi - (B +C + D)/a*∑mi he wants to be e.g. pH ≈ ∑a1*mi*pHdi/∑AI*mi - (B +C + D)/∑Ai*mi will give a better answer than pH ≈ ∑mi*pHdi/∑mi - (B +C + D)/a*∑mi .
I have always found the Brewers Friend calculator to give answers closest to those obtained by solving A(pH) + B(pH) + C + D(pH) = 0. This is in part because it is clear that Kai understands the chemistry. According to his 2009 paper we had apparently discussed prediction mash pH prior to then and I vaguely remember such discussions in which I recall I was pretty negative suggesting that the only way to do the problem was to use malt titratable acidity and I didn't think it was going to be possible to account for lot-to-lot, season-to-season etc. variations. I still think that's a problem. I had, even before that time period done a handful of malt titrations but was unaware that malt doesn't hold still while you titrate it. It just boggles my mind to think that this was 20 years ago!
In any case Kai went ahead and did titrations on a pretty good sized ensemble measuring both pHDi and an average value for a which his calculator apparently uses to predict mash pH shift from specialty malts. It is, thus, not surprising that his results resemble mine closely especially since when I don't have values for a1, a2 and a3 I'll estimate a1 from his titration data.
Other spreadsheets seem to take a more empirical approach which, while I have no direct knowledge, seem to typically start with a mash pH for base malt based on type or color and then compute shifts relative to that based on alkalinity (or bicarbonate content) of the water, the colors of high kilned malts or similar considerations and the strengths of added acids or bases. I do seem to recall that Martin commented somewhere that BW was based on Kai's work but I don't have any more information than that.
Ken Schwartz (KennyEddy) I haven't heard a peep from in 20 years. He told me that I wasn't nearly as crabby in person as he thought I would be from my postings so keep that in mind when you read my stuff!
I have always found the Brewers Friend calculator to give answers closest to those obtained by solving A(pH) + B(pH) + C + D(pH) = 0. This is in part because it is clear that Kai understands the chemistry. According to his 2009 paper we had apparently discussed prediction mash pH prior to then and I vaguely remember such discussions in which I recall I was pretty negative suggesting that the only way to do the problem was to use malt titratable acidity and I didn't think it was going to be possible to account for lot-to-lot, season-to-season etc. variations. I still think that's a problem. I had, even before that time period done a handful of malt titrations but was unaware that malt doesn't hold still while you titrate it. It just boggles my mind to think that this was 20 years ago!
In any case Kai went ahead and did titrations on a pretty good sized ensemble measuring both pHDi and an average value for a which his calculator apparently uses to predict mash pH shift from specialty malts. It is, thus, not surprising that his results resemble mine closely especially since when I don't have values for a1, a2 and a3 I'll estimate a1 from his titration data.
Other spreadsheets seem to take a more empirical approach which, while I have no direct knowledge, seem to typically start with a mash pH for base malt based on type or color and then compute shifts relative to that based on alkalinity (or bicarbonate content) of the water, the colors of high kilned malts or similar considerations and the strengths of added acids or bases. I do seem to recall that Martin commented somewhere that BW was based on Kai's work but I don't have any more information than that.
Ken Schwartz (KennyEddy) I haven't heard a peep from in 20 years. He told me that I wasn't nearly as crabby in person as he thought I would be from my postings so keep that in mind when you read my stuff!
