Subject: boiling brewing water, pH, and skunky beer
Date: 1989-05-16 02:16:00 GMT
RE: Increases in pH after boiling.
Carbonic acid is a weak, unstable dibasic acid which is formed in
solution by water and dissolved carbon dioxide. One effect of
boiling is to drive the carbon dioxide (as well as all gases)
from the solution. Once the solution cools, shouldn't the pH be
higher according to the following formula?
2H+ + CO3-- ------->H2CO3 -----------> H2O + CO2
The length of the arrows signify the tendency of the reactions to
proceed. I am a little surprised by the final pH that Peter
Soper reported for his water (>pH 9.0). Peter, does your water
contain alot of dissolved carbonates? You might consider having
it tested. I believe that one remedy is to lime (CaO) well water
to soften it and control pH problems.
When you boil your wort, do you add gypsum? To acidify the wort,
the brewer can add gypsum and/or citric acid (should be the free
acid NOT sodium citrate). I usually treat my brewing water with
both, since I can not reach my brewing pH solely with gypsum. If
I add too much gypsum I get water which is too hard. Citric acid
does not appreciably detract from the flavor of the beer, and can
rapidly change the pH of the water.
Erik A. Henchal
Oh, one last note. Mr Tehennepe described the production of what I interpreted
to be "skunky" beer. This is of course the classical description of "light-
struck" beer. Was your fermenting beer exposed to excessive amounts of light?
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