These are some pH measurements I took while brewing a Munich Dunkel last night, in case anyone finds them interesting. The grain bill was 10.5 lbs. Munich (Best Malz) and 6 oz. of Dehusked Carafa II (added during the sparge).
Mash (3.4 gallons of distilled with mineral additions) - 5.37 (Bru’n Water predicted 5.4)
Infusion (2 gallons of distilled) - 5.48
Batch Sparge (3.1 gallons of distilled) - 5.55
Pre-boil - 5.49
Post-boil - 5.44
I was surprised by the rise in pH during the sparge since I added the Carafa at that time.
The pH did not change the last time I took pre and post boil measurements, so that was also something I did not expect.
I’m using an MW101, but there is definitely some variability in my accuracy. Samples were at 72 degrees F.
Everything looks pretty good. I guess a little lower pre and post boil ph wouldn’t hurt but seems to be in range. I also do not see a drop in boil ph at times, it seems to be random. but I have noticed that as well…or sometimes its only a very small drop.
It makes sense that the infusion of distilled diluted the acidity of the mash and it raised the pH a bit. Distilled is technically neutral, but your water:grist ratio changed… so the thinner mash buffered the available acidity. Assuming you didn’t add any additional acid in the process.
I’ve been experimenting with using 10% phosphoric acid to lower the pre-boil pH, trying to get a feel for how much it takes to hit a given target. I need to do some more research on what exactly that target should be.
I was expecting the rise from the first infusion (which I could easily control with a little acid), but I was surprised by the rise during the sparge because I thought the addition of the carafa would counteract it (though it’s not why I added it then).
Even powdered, it takes time for those malts to completely hydrate and the acid distribute through the mash completely. If I recall, the acidity from a small dose of black malt isn’t all that significant, unless you are really dropping pounds of it.