[Silver_Is_Money]

Presuming that Bru'n Water did predict a mash pH of 4.55, we can derive that ~23.4 grams of baking soda are required to move a 9.35 Kg grist from 4.55 pH to 5.4 pH as follows:

(5.4-4.55) = (11.9 x grams_Baking_Soda)/(35 x 9.35)
0.85 = (11.9 x grams_Baking_Soda)/327.25
11.9 x grams_Baking Soda = 278.2
grams_Baking_Soda = ~23.4

If Bru'n Water is saying that 14 grams of baking soda will provide sufficient mEq's of alkalinity to move a 9.35 Kg. grist from 4.55 pH to 5.4 pH, then I'm at a loss as to how to explain the means by which it is deriving an answer of 14 grams instead of 23.4 grams.

[goose]

I wanted to add to Brewbama's assessment on pH change during the mash.  I made my Irish Red yesterday and took two room temperature pH measurements during the mash, one at 15 minutes in and one at 30 minutes in.  I would have continued with additional measurements for the remainder of the mash but I had to adjust the pH up a bit after he second measurement as it was a bit low (5.15) when I doughed in.  I brought it up to 5.4 with pickling lime.  Normally I hit what Bru'n Water predicts for this recipe so the lower pH in this batch was an anomaly.
I noticed that the mash pH only went down about 1% (0.05 pH units) from the 15 minute measurement and the 30 minute measurement before I had to adjust.  I normally would not wait that long to do so but I wanted to to get some empirical data, although this was a small data sample of measurements, on the change in pH between the first and second measurement  This observation is telling me that if you are in the desired range, the change over the entire mash (I only mash for an hour) is not going to make that much of a difference.

[BrewBama]

I went back and looked at my notes from that series.  Though a cpl brewdays were +/- . 01 pH over the series, my worst case was .03 (below).  ....which could be due to operator error or some other variable.

The samples were taken from the recirculating return stream, cooled, and measured. For some reason I can’t find temp data but they were cooled to ‘room temp’ — whatever that is. I am definitely not running lab conditions and there can absolutely be chinks in this data:

20 min 1.045, 5.47 pH, 65% of OG
40 min 1.056, 5.47 pH, + 11 points, 81% of OG (+16%)
60 min 1.060, 5.50 pH, + 4 points, 86% of OG (+5%)
80 min 1.065, 5.44 pH, + 5 points, 94% of OG (+8%)
90 min 1.069, 5.46 pH, + 4 points, (+6%)

At 100 and 120 minutes I was getting very little SG increase and pretty much the same pH in the early brewdays, so I cut it back to 90 min in the later brewdays. Each brewday follow a very similar SG pattern. ...nearly identical.

Given another system, volumes, additions, settings, processes, etc., and a more controlled environment, differences could and probably would result.


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