Recovering silver from exhausted photo baths
Toronto. In the days of films and glass plates, the job of a developer solution was to convert the silver halides in the emulsion to metallic silver in proportion to the light intensity hitting the molecules. The process had to be slightly alkaline to work, hence an acid stop bath to ‘stop’ development. The fixer liquid then removed the remaining silver halides to render the emulsion insensitive to light. A final wash would get rid of any residue.
Some silver or silver halides likely contaminated the first two baths, but an exhausted third bath (fixer) was saturated with silver halides. When the cost of extracting silver from exhausted photo chemistry was less than the value of the recovered silver, people searched for exhausted liquids to buy and refine.
I remember a friend some 60 years ago telling me about how old fixer baths were laced with silver halides and could be sold for recovery of the silver – I never followed up on the idea. At the time, it was acknowledged that the photography industry was the major user of metallic silver by far.
In this day, we all are aware of “recycling” and “Blue Bins” – aggregated contents are separated (paper, plastic, aluminum, etc.) and sold to companies that extract and reuse the basic material.
This old ad from an 1891/2 issue of the “St. Louis and Canadian Photographer” magazine suggests one enterprising company who was on the search for old photo chemistry baths. Thanks to my good friend, George Dunbar, for sharing this quaint ad from over a century ago.
