Quote Originally Posted by gainer View Post
TEA is hygroscopic. The weight gain at equilibrium is 20% at 50% humidity, 25% at 60% humidity . Perhaps that is another way a lotion pump can help. It would minimize contact with air while decanting from storage. If the TEA solution is heated to 250F not long before storage, it ought not have much water in it initially.

50% humidity is not uncommon in these parts.
50% humidity is actually fairly low. I know that APUG members live in all sorts of climatic extremes, but in a temperate climate the outside humidity is often 60% to 90%. When you have the heating on the relative humidity inside becomes less, even though the absolute humidity is unchanged. I wonder if it's the relative humidity or the absolut humidity that is relevant in the case of TEA based developer absorbing water from the air, a little bit every tme the bottle is opened.

For this reason and because of possible oxidation I generally don't use the last bit of developer in the bottle, if it's a highly concentrated type which takes many openings of the bottle to use up.