Waking a dead thread here because I'm consistently seeing a strange issue balancing the pH of my sparge water, and this issue seems to belong here.
Background: I use the Brunwater spreadsheet to great effect balancing my mash - whether it's a lager or a porter - really great. I brew on a 3-vessel HERMS system and always start with 12 gallons of sparge water in the HLT regardless of how much I intend to use (most often with a 10g batch I use most of it). I use the Hanna pHep meter with a good/new probe.
I always add the prescribed amount of salts and acid to the sparge and let it mix/recirculate for at least 10 minutes during the temperature ramp to mash-out 170F. What I've noticed is that if I add, say, 1.3cc, and then extract, cool and measure a sample pH at something like 6.2, I want to add a little additional lactic to bring the down to 5.6-5.8. If I then add 0.2cc, wait 5-10mins, extract, cool and measure a new sample, it will have dropped dramatically to something like 4.7 all of a sudden.
Can anyone explain this weird phenomenon? Is the changing temperature of the sparge water affecting the pH (keeping in mind I cool all samples to room temp before using my pH meter)?