I must confess that I never have used glycerine as an additive to my
fermentation locks. I always ensure that the solution of Sodium/potassium
Metabisulphite occupies a good measure of the available "u bend". I always
cap my locks with a suitable cap which seems to prevent major evaporation
loss. Clearly there is virtually no activity in the wine except for
expansion and contraction of the bulk of the wine and I ensure that the
quantity of solution is such that there will be no "suck back" into my
wine -- just air in extreme circumstances -- but then the head space above
my wine is minimal..
I should be more worried about suck back of a glycerine solution than of SO2
solution

--
Trevor A Panther
In South Yorkshire, England
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