trying to understand PH readings...help!

[symphony1975]

hello,

recently i posted a question about my actual PH readings being different than what EZ water calc predicted and I got some great informative replies. I firstly wanted to eliminate the possible error in doing PH readings of samples at different temps. So I have since done 2 more brews, ensuring my calibration solutions and mash samples all were conducted at the same temps (25 degrees)........and still i am out!!!! I was hoping for the differences between the predicted and actual readings to be the same so I could just simply compensate in future brews but alas, they are all over the shop!

ok so brew 1 was a golden ale:

View attachment golden.tiff

grain bill:
pilsner 2.62kgs
munich .87kgs
wheat .87kgs
caramunich I .27kgs

my actual readings were:

@15 min in mash 5.23
@35 min in mash 5.27

brew 2 was a black IPA:

View attachment BIPA.tiff

grain bill:
maris otter 5.35kgs
victory (looked up online an said to put as roasted) .34kgs
wheat .34kgs
chocolate .29kgs
crystal .29kgs
midnight wheat .18kgs

my actual readings were:

@15 min in mash 5.11
@35 min in mash 5.07

I tried to be tricky and aimed for the same estimated PH to see if the difference may have been the same with actual readings.

My procedure is to take a sample in a glass jar at 15 mins and then at 35 mins (after i stir the mash) (i use single temp infusion mash). then later I take the time to calibrate the meter and ensure sample temps are right. Does the PH continue to chage over time? if I leave a sample for 4 or 5 hours would it read differently? when should I take the sample? given that I always get 2 different readings from 15 min or 35 min in mash

otherwise can anyone shed any light on what I am missing?

thanks heaps....

 

[dent]

It seems to me that you're almost getting consistent results, just in proportional terms rather than absolute. Since your grain will not have precisely the same distilled water pH values as those in the sheet, your water will vary in ions week to week, and you're dealing with a pretty non linear model in the first place, all those "errors" can add up pretty easily to result in what you're seeing IMO.

Since it is not critical to get that 0.01 pH value accuracy anyhow, I would correct your expected pH values by the discrepancy you often experience (0.3ish), and by then hopefully you'll be able to get your pH readings where you want them to be with your equipment and ingredients.

 

[KaiTroester]

you can also try this calculator. It still predicts a bit higher than what you measured, but is closer.

dent made a good point about the dependency on the actual base malt DI water pH, which doesn't correlate all that well with the malt color. I loaded your two recipes:

http://www.brewersfriend.com/mash-chemistry-and-brewing-water-calculator/?id=6KDWG89
http://www.brewersfriend.com/mash-chemistry-and-brewing-water-calculator/?id=SRQYX9L

Kai

 

[ashley_leask]

How sure are you hat your water profile is accurate? Your pH readings are very low for such soft water, even w/ 15g of salt additions.