Quote Originally Posted by Photo Engineer View Post

Maybe I should point out that you had reason for your answer. Both TEA and DEA react with air, but not oxygen (readily). It is the Carbon Dioxide that they react with, gradually forming the carbonate salt.

This will drag the pH more acidic.

That explains why a working solution of PC-TEA or the like, made with my hard well water and left standing in an open pitcher, will turn cloudy as would a developer like Dektol. I'm assuming that the TEA makes a carbonate out of CO2 from air which it hands over to the Mg and Ca in the well water making limestone as the cloudy stuff. OTH, even a glass of well water standing open should become cloudy. Anyway, it's very good drinking water from 110 feet down. If I ever get a water softener, I shall put a tap between the well and the softener for drink.