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Discussion in 'B&W: Film, Paper, Chemistry' started by Snapper, Aug 31, 2004.
Can anyone tell me the shelf life of Viradon toner once mixed up?
I have used it for up to 4 weeks (storing in bottles between sessions).
The more used it gets, the fastest it is and the lightest brown it gives.
At least two years - will let you know when I have to mix new
I recently used some for only a few sheets and put it in a bottle. It was stored in darkness. When I came to use it maybe a month later, it had a scum which I think was probably elemental sulphur. The Viradon might have been contaminated with a very little sodium sulphite, since I put one print back in the toner after rinsing in it and deciding to give it a little more toning. Would that have caused the breakdown?
Could well be. Viradon is sodium polysulfide, which will react with sulfite to gice thiosulfate and sulfur. It will decompose all by itself as well to give sulfur, or with oxygen to give sulfite and sulfur - and thus thiosulfate and more sulfur, which reacts with oxygen to give sulfate and even more sulfur...
It basically reacts with anything, and gives sulfur as a result. But it lasts for a very long time if you can keep "anything" out of it.