If you search the forum thoroughly enough you'll find numerous threads on this subject. I tend to go with the workflow posted by Doremus Scudder, who explains that toner in water will last indefinitely, but when diluted with HCA it's the HCA that becomes exhausted first. So you'd have to discard this solution when the HCA is exhausted, thereby wasting the selenium. When the toning time gets longer, he simply replenishes it with 30ml of fresh toner per liter of toner solution and repeats as needed to maintain a reasonable toning time. He filters the toner solution both before and after a session using coffee filters. This procedure is preceded by two-bath fixing in rapid fixer. The toned print then goes directly into Ilford Washaid or HCA (1+4), then a thorough washing. I think I've recalled all this accurately, but it's all in the archive if you take the time to find it.
I love being referenced! It appears I've become somewhat of an authority on this technique, so I'll chime in as well.
Silveror0 got my workflow exactly right. I'll just add a few things. First, I've been replenishing and reusing selenium toner for a couple of decades now. I have two gallon jugs, one strong, one weak, that have been going for well over 10 years. No problems whatsoever. And, just so you know, I routinely test the last print through the fixer/toner/wash for residual silver and hypo. Never a problem.
Kodak's recommendation for mixing selenium toner with HCA is old, and from an era when the awareness of discarding heavy metals into the environment/sewage system was not as keen as it is today. Plus, discarding a product before its useful lifespan is up, while uneconomical for the consumer, is "good business" for the manufacturer. (No, I'm not really that cynical, but things like this are common practice in marketing. I once read that one of the most brilliant strokes of marketing in the shampoo sector was simply to add the word "repeat" to the instructions... But I digress.)
Unfortunately, Ansel Adams recommended the practice of mixing toner with HCA in his books, so the practice became rather widespread among those who learned processing from them. Now, the consensus seems to be that it is wasteful and possibly environmentally irresponsible to discard large amounts of still-active selenium toner.
A couple of remarks about replenishing and reusing the toner: First, I always filter the toner into the toner tray using a coffee filter. This removes the black precipitate that occurs in used toner (I believe it is silver from the fixed-out halides reacting with the selenium to make selenium sulfate, but I'm not sure. Maybe Gerald or one of the chemists can confirm this?). Filtering also removes any slime or bacterial growth that may occur. I've had that happen a time or two over the last 20 years.
When toning times become longer than desired, I replenish at about the rate silveror0 mentions; 30ml/l, but this is just approximate. I'll often just add a splash from the bottle of concentrate. If the times are still too long, I'll add a bit more. I'm not concerned with the exact dilution, since I tone visually. For me, a comfortable toning time is most important. If the times are too short after replenishing, then I'll dilute a bit.
I transfer my prints directly into the toner from a "paper-strength" rapid fixing bath (Ilford Rapid Fix or Hypam at 1+9). At this dilution, the fixer is neutral enough not to cause staining. The 1+3 dilution many use is likely too acid for this practice, so a less-acid fix should be used before directly transferring the print to the toner, or a thorough wash step should be added between second fix and toner (which seems like a colossal waste of time to me...).
After toning, I filter the toner solution back into its storage bottle (a brown 1 gallon photo-grade plastic jug) and save it till the next session.
As silveror0 mentions, I also just transfer my prints directly from the toner into the wash-aid. This I make myself from sodium sulfite and metabisulfite and use one-shot. Transferring without an intermediate rinse reduces the capacity of the wash-aid somewhat, which I take into account. Again, it seems a colossal waste of time and space to have to rinse in between.
If you've already mixed your toner with HCA, don't discard it. You can simply replenish it and reuse it, making sure to follow your toning with a fresh wash-aid bath. Having a bit of oxidized sulfite in the toner won't hurt it a bit.
Hope this helps,
Doremus
