Selenium Toner question

[dave4242]

Hi all, how long does a batch last? is it like fixer that gets exhausted?
thanks!

[Bruce Barlow]

A long time, but as you go on, it does get exhausted and your toning times get longer.

If I use a 20:1 dilution, from time I'll add an ounce of toner. Close enough.

[John Layton]

I really don't get Kodak's "shelf life/capacity" guidelines for KRST. I've had the same gallon of 1:19 for over a year...have never added any concentrate to this - and still get a nice (slight, just as I like it) tonal shift, in about seven minutes, on Ilford Classic - having done quite a few 30x40's, 20x30's, and 16x20's over this time period.

But come to think of it, my time for this amount of shift started out at about three minutes...and now its closer to ten minutes. Hmmm...probably should just go ahead and throw an ounce or two of concentrate into the mix!

[esearing]

My stock KRST gallon bottle is 20+ years oldBut I have no idea when it was opened. Diluted 1:6 My current batch has lasted for two years with no change for me, but I am not very prolific in volume. Stored in glass bottle.

Tips - Whatever dilution you use, when fresh, measure the time until color shift occurs in a black region on a test print, write it on tape on the bottle with the date. Then you can test before use on important prints.
Time to color shift of max black will vary by paper and developer and washing method. I let all prints dry before rewetting and toning but you can go straight from wash to toner.
I made an 8x10 fully exposed sheet of paper (black) and cut it up for test strips. I also have several sheets with a range of tones light to dark stripes to test with other toners.
Label them on back with pencil if using different papers and developers.

[PRJ]

Back in the day peeps used to mix Selenium toner with Hypo Clear because Answell did it. I always thought that was kind of dumb because the Hypo Clear didn't last as long as the toner. Maybe that is why you are confused about the life of it.

Like others, I just keep using it and replenish it. If you get any black specks or sludge in it, just filter it.

[koraks]

Unlike others, I have my doubts about the longevity, but I generally use selenium for quite heavy toner. For consistent, repeatable results I prefer to use a smaller volume for a single session or even a single print. About 20ml tones a 5x7"; the dilution can be chosen for the preferred extent of toning.
I do save the toner instead of discarding it, but I find it throws down a brown or black sludge within a day. It seems that at least part of the selenium drops out of solution. Perhaps this is due to incomplete washing, as I can imagine that remnants of acidic fixer and whatever additives it has (stuff like boric acid) may interfere with the toner. I'm not sure as I haven't investigated it deeply.
The saved toner does remain effective, although it's effectiveness tapers off significantly in my experience.
BTW, I use Adox selenium toner, but I doubt that it's fundamentally different from KRST.

[dave4242]

Thanks everyone, really appreciate the insight

[Doremus Scudder]

I've written about this a lot here and over on Photrio, but the information doesn't seem to be propagating very well...

Selenium toner working solution can be easily replenished and reused indefinitely as long as you filter it before use (coffee filters work fine for me).

When toning times get too long, simply add a bit of stock to the working solution. Very little is needed; if you add too much, you can always dilute the solution to get your toning times back to the preferred length. Impurities will precipitate out and get caught in the filter, keeping the solution fresh. Plus, after a while, the annoying ammonia odor disappears (yes, the toner will work just fine without the ammonia smell).

I have a couple of gallons of KRST working solution (a weak and a strong batch) that have been going for 10 years or more. They still do the job just fine.

Myth busting: Simply toning at a giving dilution for a given time will not give consistent results. First, the toner weakens slightly with each print run through it, and toning times to achieve the same effect gradually increase. Second, the impression of tonal shift on the print itself is influenced by a number of factors; the paper, the distribution of tones in the print, the developer used, etc. Toning by inspection is the more reliable way to get the desired amount of toning. That means having a good light source and an untoned print handy when toning so the amount of tonal shift can be more accurately assessed.

More myth busting: Toning in selenium does not give the print any real protection or "archival" qualities unless the toning is done to completion or almost to completion. Most of us tone just slightly, and the amount of protection offered with that amount of toning is negligible. Those who tone "for five minutes in KRST 1:19" as a matter of course just because it's "archival" aren't helping the longevity of their prints much. No tone change = zero protection. Better to process with fresh chemistry and wash well.

Also, I find it both irresponsible and uneconomical to dump selenium into the waste-water systems if it's not necessary. The proper way to discard spent selenium toner (if you must discard it) is to first use it till the toning times become really uncomfortably long, then toss a few scrap prints into the toner and let them sit overnight to scavenge as much of the remaining selenium from the solution as possible.

One more thing: Ansel Adams and others recommended mixing selenium toner with wash aid (Hypo Clearing Agent) to save a step. This is wasteful. Either you have to discard a still very active toning solution when the capacity of the wash aid has been reached, or you end up toning a lot of prints that don't get the advantage of a wash aid. I'm sure this made Kodak a bit more profit when the awareness about discarding heavy metals into the environment was not as keen as it is today, but it is no longer best practice. Better is to have a separate wash-aid step following toning.

Hope this helps,

Doremus

[Oren Grad]

Doremus -

One aspect of KRST that's not addressed by your observations: selenium isn't the only ingredient in KRST. What happens to the concentrations of ammonium thiosulfate and sodium sulfite when the working toner solution is stored for extended periods, reused and replenished in that way? (The fact that the ammonia smell goes away is presumably telling us something.) What are the implications of that for performance as a toner, and for the clear and wash cycle that's required afterward?

[Doremus Scudder]

Doremus -

One aspect of KRST that's not addressed by your observations: selenium isn't the only ingredient in KRST. What happens to the concentrations of ammonium thiosulfate and sodium sulfite when the working toner solution is stored for extended periods, reused and replenished in that way? (The fact that the ammonia smell goes away is presumably telling us something.) What are the implications of that for performance as a toner, and for the clear and wash cycle that's required afterward?

Owen,

I'm aware that the concentration of other components in the toning solution may change. However, I have observed no loss of toning activity in toning baths stored for long periods of time. I find the lack of ammonia odor an advantage. However the composition of the toning bath is changed by replenishing and long-term storage, it seems to have no effect on the ability of the toner to work..

I was at first worried that fixing by-products could accumulate in the toning bath, either rendering it unusable or contaminating prints. That seems not to be the case. I suspect that the precipitate that forms and is subsequently filtered off carries with it the contaminants. FWIW, I routinely test my prints for residual hypo and residual silver compounds (HT-2 and ST-1 tests respectively). I test the last print through a batch of fixer almost every run. My prints never have even the slightest stain, so they're passing the tests with flying colors. I've been toning this way for 15 or more years, testing as I go and have never had a problem.

I believe Bob Carnie and several others on this forum and Photrio have adopted a regime in which they use replenished selenium toner with success as well.

Hope that addresses your concerns.

Best,

Doremus

[Oren Grad]

FWIW, I routinely test my prints for residual hypo and residual silver compounds (HT-2 and ST-1 tests respectively). I test the last print through a batch of fixer almost every run. My prints never have even the slightest stain, so they're passing the tests with flying colors. I've been toning this way for 15 or more years, testing as I go and have never had a problem.

With rigorous testing like that you should be fine indeed. I don't think there is anything more you could reasonably do.

[Doremus Scudder]

Owen,

Testing isn't really that difficult. I have the solutions on-hand and just put a drop of each on the margin of last print of a run through the fixer, wait three minutes and check for stain. Then it's back in the wash for a few minutes to wash out the chemicals on the margin. EZPZ.

FWIW, you can use KRST 1+9 instead of the ST-1 (which doesn't keep quite as well). I test out of habit; I'm pretty confident that I'm using my fixer wisely (i.e., two-bath and not to capacity) and washing long enough.

Back to the toner: as long as whatever is in the toner that's not toning the print washes out, there should be no problems. Insoluble silver compounds in the toning bath would precipitate out if they were ever formed. If prints are well-fixed before hitting the toner, there shouldn't be any carry-over of unfixed or partially-fixed thiosulfates to the toning bath in the first place.

Best,

Doremus

[Joe O'Hara]

Thanks Doremus, it sounds like as usual you've thought this through very well.

When I finally decide to start over with a new batch of KRST, I dump it into the same bucket that I dump
my used fixer. That bucket has a couple of pieces of steel wool in it to (it is hoped) scavenge the silver from
the fixer before it gets into my septic system. I figure the selenium in the old toner will plate out on the silver
that has plated out on the iron, but I'm not a chemist. After a week or three down the pipe it goes.

Based on what I've read here, I'll just keep on filtering the KRST solution and replenishing it as needed. It does
seem to work fine once I've gotten all the crystals and sludgy bits out of it. At my rate of usage I'll never need
to buy another liter of concentrate again.

[esearing]

For archival protection I remember reading a scientific study/article that proper washing and mounting protected the image more than selenium alone. It suggested that "pollution" from the rear of the image and interaction with the paper was more damaging than the silver/emulsion surface.