Originally Posted by brian steinberger
Originally Posted by gamincurieux
Let me clarify. First, Brian's method: While not completely bad practice, there is still quite a bit of selenium left in a toning solution even after the times become uncomfortably long. Determining when selenium toner is "exhausted" is not all that easy. Even harder is knowing how to "dump it properly." As I mentioned, selenium, which is a toxic heavy metal, is not removed by municipal water treatment plants. I'm not sure what the hazmat people do with it either. The time or two I took used toner to the hazmat facility near me, the people there were flummoxed and just marked it "photographic waste," the same thing they marked the fixer (which should have gone to silver recovery, but likely did not...).
If you wish to discard selenium toner, try to use it till the times become uncomfortably long, then toss a few scrap prints into the tray and let them sit overnight. This will scavenge even more of the selenium from the solution, leaving very little to discard. Then discard into the municipal sewer system if your city/community allows it. If not, then bottle it up and take it to the hazmat facility.
Or, you can save yourself the trouble and inject even less of the selenium into to environment by replenishing.
Yes, used toner develops "silver flakes" (I think they are really a silver selenite compound). These, however, are easily filtered out.
And, someone here once maintained that selenium toner was exhausted when the ammonia smell was gone. This is absolutely not the case. My replenished toner solutions never smell of ammonia and they tone just fine and rapidly.
As for how much toner concentrate to add when replenishing... well, this is a bit trickier. I judge the amount of toning I like visually, i.e., when the right amount of color change has taken place. When it starts getting too long to reach the desired color change (I think 8 minutes is too long for me, but sometimes 6 minutes is too long too...), I add a bit of the concentrate. I rarely measure, just pour a bit from the bottle, but if I had to estimate, it would be 50 ml per liter as a starting point. Add this; if times are too slow, do it again. If times speed up uncomfortably, dilute with some water to slow things down.
I realize this sounds imprecise, but it really isn't. Toning "1+19 for five minutes to enhance D-max" is a myth. The first print you put through a weak solution of toner uses up a bit of the selenium. After a few prints, it is no longer "1+19" and, to be consistent, the time should be adjusted to compensate. But, how much? Who knows. Many don't bother and end up running prints through too weak toner for too little time and getting no benefit (or result) whatsoever.
If you can't see a change, either in D-max or in image tone or both, you aren't getting any toning. Tone to a point you can see, pull the print when the desired change is reached and adjust the dilution of the toner to keep the time of doing this in a comfortable range. That is much more accurate.
Hope this helps,