Doing a Hefeweizen this weekend and I plan to mash-in at 111 F for a ferulic acid rest for 10 minutes, then pull a decoction.
My question is this: When doing any "acid rest", the mash will become slightly more acidic, yes? But how much more? Will it keep going, or is there some sort of buffer effect that dictates after it drops a certain amount, it can drop no further?
Bru'n Water calculations show that at mash-in, my pH should be around 5.5, and I'd like it to be around 5.2 during conversion. When I do my rest at 111 F, will I see enough of a drop before pulling my decoction, or should it take longer? Should I just add a few ml of 10% phosphoric instead of waiting around for the pH to drop on its own?