Quote Originally Posted by Brontosaurus View Post
Interesting that you bring up old photographic processes with this. As I recall, one of the tricks to stabilizing a salt print was to dip it in something like a 2% to 4% sodium chloride solution before moving to the hypo. This was to lift off most of the unexposed silver chloride so that the hypo did not exhaust itself in having to serve the same function. From Wikipedia, I read that sea water ranges to approximately 3.5% saline, so such a solution would appear to have been approximating it. There I also read that sea water has a typical pH range of 7.5 to 8.4, so that would make it mildly alkaline, no?
OT but I believe you're thinking about a stop bath to neutralize the developer in film processes. Developer depletes the fixer. Most folks just use plain water but a little citric in the pre-fix wash IIRC will help.

In platinum print making, the developer is not exhausted and actually gives a warmer tone with continued use. I use potassium oxalate and the light sensitized ferric oxalate on the paper is converted leaving Pd/Pt metal, but the non-exposed ferric oxalate must be removed because it is still UV sensitive. Anything that chelates iron works, like citric acid or EDTA, but 1-2% hydrochloric works really well. It must be neutralized with a base solution wash.

Bottom line, many acids and chlorides remove iron or convert iron to compounds we don't like on our razors, like iron oxide (rust) and iron phosphate (from phosphoric acid as in cola) which is protective but black. Bluing on guns does the same protective function and some razor tangs were blued or blackened. I have modded Gold Dollar with a 'blackened' blade which is actually pretty neat.

Cheers, Steve