He did correctly point out a flaw in the rule of thumb that I proposed between RA and SRM. He pointed out that if you design a really dark beer, the required RA goes through the roof.
The other obvious flaws being that your calculation cannot conceive of a negative RA value and that the calculation needlessly oversimplifies a complicated concept when many people have dedicated countless hours to developing applications to model non-ideal solutions.
Unfortunately, thcipriani goes on to say that the correlation between RA and SRM is tenuous at best. Unfortunately he is quite wrong with that statement. He did provide a couple of references from AJ and Kai that actually do provide a correlation between roasted malt acidity and their color.
I agree roasted malt is acidic; however, SRM is not indicative of the amount of roasted malt used in a mash - that's what I found in Kai's research; however, I guess you always find that for which you are searching. You have not offered any proof that there is any sort of strong correlation between SRM and and pH. Can you point to any studies thats conclusion is that mash pH can be predicted solely on SRM? It's like predicting the weather - I'm not arguing there is science to support that SRM has some correlation to mash pH. I'm arguing that if I test my mash pH I'm always right about my mash pH. If I use one of the available spreadsheets on the internet (especially if I'm starting with a profile that can't exist) I'm not going to be right 100% of the time. If I go outside and it's raining it doesn't matter what the weatherman says.
thcipriani goes on to say that the vast majority of water needs no adjustment. That statement is quite incorrect. The historical beer styles that grew out of the world's brewing centers are cases in point. There is no way that a brewer in Dublin could EVER hope to brew a good pale beer with their water and conversely, there is no way that a brewer in Burton could ever brew a good dark beer with their water WITHOUT ADJUSTING THEIR RESPECTIVE WATERS.
I never claimed that Dublin water needed no adjustment to brew a pale beer. I said that the majority of water needs no adjustment - extremes are exceptions. I don't think anyone would disagree with the statement that Dublin and Burton-on-Trent are very extreme waters. If there's a brewer out there with that kind of water then, yeah, they'll need adjustment - the 800ppm SO4 as the ion would be a good tip that your water is atypical.
Its also humorous that thcipriani goes on to state that if brewers are worried about their mash pH they should get a pH meter and then adjust their mineral or acid content. He is espousing exactly the same thing that I'm stating with chemistry adjustment excepting that he is expecting a brewer to figure out what to do while potentially destroying a few mashes in the process.
I'm glad I can humor you. I don't espouse anything with that statement other than a pH meter can give a brewer that's worried about their pH piece of mind. I think that once a brewer has a pH meter they'll be able to make informed decisions about which ions to add to their water to give them an appropriate mash pH and not blindly add salts and acids that needlessly destroy their mash by taking it out of the correct pH range. You seem to think that by measuring mash pH and adding CaCO3 or Lactic acid that it somehow ruins a mash when, in fact, adding a huge amount of CaCO3 without measuring your mash pH would do the same thing.
I really feel we're circling the same point - water's complicated and brewers need to be conscious of their pH. The difference here is that you espouse that a spreadsheet is highly accurate while I believe that a properly calibrated pH meter is the best tool.
Non-ideal solutions (like water) are complicated systems to model. If a brewer makes additions based on readings they get from a calibrated pH meter they're going to be right 100% if the time. If they use a spreadsheet, or worse yet, an oversimplified formula they could be wrong. I'm just asking brewers to look outside before they decide they don't need an umbrella.