A proposal whereby to test the validity of RA (Residual Alkalinity)

[Silver_Is_Money]

Residual Alkalinity (when a positive value) represents "only that fraction of a mash waters Total Alkalinity which raises mash pH". And when RA is negative it has the opposite effect upon mash pH, causing it to fall.

Mash water which has Alkalinity, Calcium, and Magnesium, is comprised of one component which raises mash pH (that being Alkalinity), and two components which work to lower mash pH (those being Calcium and Magnesium).

If there is sufficient of either or both Calcium and Magnesium present within ones mash water whereby to have these ions downward impact upon mash pH exactly balanced by the waters Alkalinity induced upward shift in mash pH, then mash pH is completely unaffected by such water, and this water is considered thereby to have Zero Residual Alkalinity.

With the above in mind, here is the proposal:

1) Purchase some distilled or deionized water. RO will likely not be good enough here, unless its TDS is below ~4 ppm.
2) Carefully make up a rather high mineral content water containing Ca, Mg, and Alkalinity, from the distilled/deionized such that its calculated RA is Zero.
3) Test mash a carefully weight measured quantity of base malt in a fixed volume of distilled/deionized water and measure its Wort pH at room temperature.
4) Test mash the same malt and malt quantity in the same volume of made up high mineral content, but zero RA water, and mash at the identical temperature, and for the identical time as for the mash carried out in distilled/deionized water.
5) Record the room temperature Wort pH for this mash at the exact same temperature as for the distilled water mash.
6) Compare the two mash pH results. If they are identical, then RA as we currently perceive it is factually sound. If the two pH's differ, then the concept of RA as it is currently understood is invalid.

*Pull pH samples at no earlier than 30 minutes into the mash. Whatever sample time you settle on, use it for all samples.

Now repeat the all of the above, but this time mash with 9L-10L Munich malt instead of a base malt.

The results of a multitude of tests as described above will either validate or invalidate the concept of Residual Alkalinity.

 

[Silver_Is_Money]

PS, I've TDS tested some terrible DI and distilled waters over the years, so I would advise testing these waters as well to satisfy that they are at or below 4 ppm TDS.

The best RO water I ever TDS tested read 2 ppm. Better than most distilled. Deionized water should test at zero.

 

[Donoroto]

Seems sound, but please clarify for me:

Help me remember the chemical makeup of alkalinity.

Why repeat with Munich malt?

Thanks!

 

[Silver_Is_Money]

Mainly (for fresh water at normal pH's) Alkalinity is comprised of the bicarbonate ion, and the two correspond on an EQ Wt basis whereby:

Alkalinity ppm (as CaCO3) = 50/61 x Bicarbonate (HCO3-) ppm

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In 2015 chemists Roger Barth and Rameez Zaman peer review published:
'Influence of Strike Water Alkalinity and Hardness on Mash pH'

In it they found that the 6 decades running accepted Kolbach denominator of 3.5 for Ca++ mEq's is bogus, and what they found is that:

The actual Ca++ denominator value for 'their' tested lot of Pilsner malt = 14.8 (vs Kolbach's 3.5)
The actual Ca++ denominator value for 'their' tested lot of Pale Ale malt = 7.2 (vs Kolbach's 3.5)
The actual Ca++ denominator value for 'their' tested lot of Munich malt = 12.2 (vs Kolbach's 3.5)

They did not test Mg++ to see if it was similarly nowhere near Kolbach's 1951 findings. But their findings for Ca++ pretty much destroy RA computation based upon Kolbach. And instead indicate that the concept of RA is wildly variable.

The oddity in the Barth and Zaman findings (which in my opinion taints it and puts it into question as to its overall validity) is that they tested at only 5 minutes into each mash. But to their credit they did multiple repeated re-tests. Therefore to avoid this oddity I suggest testing wort at no earlier than the 30 minute mark in the mash.

 

[Donoroto]

Perfect! Thanks.

This might inspire me to obtain a way to accurately measure pH.

 

[Silver_Is_Money]

As to RA (Residual Alkalinity), what Kolbach discovered and documented for "knockout" (as in post boil and cooling, and not for the mash) was:

mEq's_RA = mEq's_Total_Alkalinity - [(mEq's_Ca++/3.5) + (mEq's_Mg++/7)]

What Barth and Zaman determined is that the above is meaningless when applied to the mash, as has been done by nigh on everyone for decades now as a means whereby to predict the downward shift in mash pH caused by the presence (or addition) of calcium and/or magnesium ions, in conjunction with the presence of Alkalinity.