Wow....I can only partially grasp all this on first read, but I look forward to getting into it more deeply. And Kai, I want to say thanks for all the absolutely great work you're doing!
Thanks. Now that I started going down that road I want to finish the work and feel I should also try to find practical advice and guidelines. And hopefully a model that also explains brewer’s experiences that have not be explained so far. W/o that it would have be waste of time.
Personally, I like playing around with grist and water compositions in a spread sheet that I’m working on which takes into account the malt characteristics that I measured. But I cannot expect that from other brewers. While a bit flawed Parmer’s approach to suggest RA targets based on beer SRM is a very practical one since most of us already calculate and target beer SRM through the use of brewing software/spreadsheets. I stopped calculating beer SRM a long time ago because I was never really interested in the actual value. If, based on previous batches, I compose the grist correctly the beer will have the desired color. Introducing a new metric like mash color, for example, to predict the needed RA would only make the process more complicated.
Only if this mash pH model can be integrated into popular software like Beersmith would I have a shot at reaching a wide audience with a more precise RA estimation. I doubt that there is actually a need for that level of precision. On the other hand, homebrewers like to tinker with things that commercial brewers don’t even worry about, so we will see.