Nacco stop bath

[pschauss]

I recently bought some Nacco stop bath from a local shop. Not only is does it have less of an odor than the Kodak stuff, but when used with Ilford rapid fix in my slot processor I seem to get less of an odor from the fixer. The label says that it contains "hydroxyethanoic".

The only negative thing I have observed is that you need to use more of it and you have to replace it more often.

Has anyone else used this stuff?

 

[Donald Qualls]

Regular acetic acid is also called "ethanoic acid" -- if the Nacco fixer is "hydroxyethanoic acid" it would likely be (assuming I'm remembering my chemistry correctly) the mono-acid of ethanediol, which I would expect to smell somewhat "sweeter" than ordinary acetic acid.

You're probably not really getting less fixer odor, but since the fixer and stop bath are normally both mostly characterized by the odor of acetic acid, you're getting less total odor. The question is, does this "hydroxyethanoic acid" stop development as well as acetic or citric acid at appropriate strength? That depends on the pH of the bath, which I don't know offhand. Lower capacity, however, is a bad thing, though not terrible as long as there's an indicator in the Nacco chemical.

Many folks use water (completely odorless) as a stop bath for negatives, but for prints it has to be changed very frequently due to carry over.