Acid rest malfunction

[bytor2012]

Hello brew lords!
I was brewing a Pilsner the other day. My plan was to use a triple decoction mash. I doughed in at the acid rest temp and hit my target temp of 100 F. I let it rest for 30 minutes and I checked the ph. It was 5.7. I, then, attempted to lower it by adding 1 g of gypsum. I gave it 10 minutes and checked the ph again. It went up to 5.82. I scratched my head...this can’t be right. I proceeded to calibrate my ph meter (hi-98128) and checked again...same result. I added another gram of gypsum. Ph 5.85. WTF? I then added .5 g gypsum and .5 g calcium chloride. Ph 5.9. Next, I added 1 oz of crushed debittered Belgian black malt. No change. What the heck is happening here??? In theory all of those things should have lowered the ph. To me, it’s like having a pot of water on the stove, applying heat and watching the temperature go down instead of up! Can anyone shed some light on this scenario?

 

[bytor2012]

Let me clarify that the incremental increases may not be exact, but the point is that the ph was rising instead of falling.

 

[dmtaylor]

How old are your calibration solutions? Shelf life is only about 1 year.

 

[bytor2012]

I used the last of the bottles, but if I had to guess I’d say I had them over a year. That being said, I brewed the same beer the very next day with a single infusion mash. I added my salts as I usually do per John Palmer’s spreadsheet and my ph was 5.3.

 

[bytor2012]

Is there some correlation between adding salts before you add grains as opposed to after?

 

[dmtaylor]

Is there some correlation between adding salts before you add grains as opposed to after?

No it shouldn't matter.

 

[Vale71]

Gypsum dissolves more easily in cold water so at the temperature your mash was at it might have taken a bit longer. How old is your PH meter? PH probes don't last forever unfortunately and erratic behavior might be one of the early signs of a probe that is about to expire...

 

[bytor2012]

I just replaced the electrode last year.

 

[bracconiere]

to bad you didn't have some phosphoric acid to try....what efficiency did you end up with? i know when i have big changes to make stuff like epsom salts aren't enough to lower it, gotta whip out the acid...

 

[bytor2012]

Yeah...I just ordered lactic acid in case that happens again.