I can't seem to find the answer to this although I feel like it must have been asked. I'm using the bru'n water spreadsheet and trying to wrap my mind around the chemistry involved. It is suggesting a bit of sparge water acidification (to the tune of .47 tsp/gallon) given my water chemistry as reported on the city water quality website (http://www.austintexas.gov/sites/default/files/files/Water/WaterQualityReports2012/wqs_2q2012.pdf). This is fine and dandy, but I am also a bit low on calcium, so playing with the Water Adjustment page it looks like I can do 1.0 g/gallon gypsum to compensate (which additionally helps push my predicted mash pH into a good place).
The spreadsheet seems to imply that I should treat my mash AND sparge water with gypsum, but wouldn't this mess with the alkalinity of the sparge water? The Sparge Acidification page doesn't seem to consider my altered water chemistry, only the water chemistry I input on the first page. So my question: should I hold back the gypsum addition from the sparge water and just add it to the kettle? Does it matter?. I'm already adjusting the sparge water using phosphoric acid, so it seems like adding gypsum as well (without knowing its effect on the pH is a bad idea).
In summary, my plan is to:
Use phosphoric acid in the sparge water to hit the right pH
Use gypsum in the mash to adjust mash pH and add calcium to the water
The spreadsheet seems to imply that I should treat my mash AND sparge water with gypsum, but wouldn't this mess with the alkalinity of the sparge water? The Sparge Acidification page doesn't seem to consider my altered water chemistry, only the water chemistry I input on the first page. So my question: should I hold back the gypsum addition from the sparge water and just add it to the kettle? Does it matter?. I'm already adjusting the sparge water using phosphoric acid, so it seems like adding gypsum as well (without knowing its effect on the pH is a bad idea).
In summary, my plan is to:
Use phosphoric acid in the sparge water to hit the right pH
Use gypsum in the mash to adjust mash pH and add calcium to the water