I'm trying to get a handle on water adjustments and pH control when using RO water as a starting point. The RO water I used gave TDS = 1 with my meter, so it seems quite good. A recent batch of American Pale Ale mash had 12.6 lbs. grain and 16.1 qts water, for a ratio of 1.28 gts/lb. I adjusted the RO water with some gypsum, calcium chloride, and epsom salt to give a composition close to that of the "amber balanced" profile in Bru'n Water. However, I did not add any alkalinity (with bicarbonate or pickling lime). Based on what I've read in the Primer and my own (limited) all grain experience thus far, it seems that in most cases it is necessary to add acid to the mash to reach the desired pH. Given that, why would I want to add any alkalinity to the RO water?
Anyway, my initial mash pH reading after 10 minutes was 5.82. So I added 0.85 ml lactic acid, expecting the pH to drop by about 0.1 unit, based on prior experience. Surprisingly, the pH dropped to 4.82. So I then added 0.5 gram pickling lime, which brought the pH back up to 5.80. A 0.4 ml lactic addition brought it back down to 5.59.
With these wild pH gyrations, it seems like the mash is behaving as if it has very little buffer capacity. This leaves me wondering whether it is desirable to add alkalinity to the RO water to give a more controllable pH adjustment, even though the inital pH will be too high. The adjusted water I used had only 13 ppm alkalinity and -31 RA. There is no indication in the primer about the need for buffering the water or adding alkalinity when making adjustments -- my understanding is that the grain itself has phosphates or other salts which provide buffering. But why did my mash show such wide pH swings? This all leaves me a little confused about the best way to adjust RO water to get the mash pH close to the desired range.
Anyway, my initial mash pH reading after 10 minutes was 5.82. So I added 0.85 ml lactic acid, expecting the pH to drop by about 0.1 unit, based on prior experience. Surprisingly, the pH dropped to 4.82. So I then added 0.5 gram pickling lime, which brought the pH back up to 5.80. A 0.4 ml lactic addition brought it back down to 5.59.
With these wild pH gyrations, it seems like the mash is behaving as if it has very little buffer capacity. This leaves me wondering whether it is desirable to add alkalinity to the RO water to give a more controllable pH adjustment, even though the inital pH will be too high. The adjusted water I used had only 13 ppm alkalinity and -31 RA. There is no indication in the primer about the need for buffering the water or adding alkalinity when making adjustments -- my understanding is that the grain itself has phosphates or other salts which provide buffering. But why did my mash show such wide pH swings? This all leaves me a little confused about the best way to adjust RO water to get the mash pH close to the desired range.