I like the idea of being able to predict mash pH and necessary adjustments w/o having to do test mashes.
When I brew Im usually doing lots of other tasks and I really dont want to spend time adjusting mash pH. Ideally Id like to skip mash pH measurements completely and have done that on a number few beers. Especially when I have brewed them before and still have the same bag of base malt at hand. I rather predict the mash pH of my planned grist and water treatments and then test only once to check if the prediction was close enough.
A test mash allows you to account for variations of malt pH characteristics that are difficult to predict from just color. But even that can be accounted for by actually testing the malt in a single test mash (with distilled water) and using the result as an input to the mash pH predictor. That works well for brewers who buy their malt in bulk.
As an example. Last weekend I brewed a Maibock using Best Vienna and Weyermann Munich II. The Vienna has a DI water pH of 5.8 but based on its color it should be closer to 5.5. This stumped me when I used malt from this bag the first time (
http://braukaiser.com/blog/blog/2011/03/30/vienna-malt-mash-ph-surprise/). This is one of the reasons why I added DI water pH entry to the Brewers Friend mash chemistry calculator. Based on my knowledge of the out of line Vienna DI water pH I was able to predict that I needed about 2% acid malt in the grist as opposed to not needing any acid malt. The predicted mash pH was 5.55 and measured a mash pH of 5.51. This was a decocted beer and I was aiming for a higher mash pH.
I have seen other brewers test DI water mash pH for their grain and Im encouraged by that development since this allows us to get around the color based prediction that is not correlating all that well.
What Im also saying is that if you use a mash pH predictor to design your water and mash treatments you are basically basing your decisions on the many test mashes I have done to develop the model that predicts the mash pH. You should also understand that it is only a prediction. Over time youll be able to judge how well this prediction works for you and you either gain or lose confidence in it.
Kai