Selenium Toner Impact On Negatives

[Jorge Gasteazoro]

Paul, I agree with Ken, there is big flaw in Wilhelm tests. Toning has two distinct mechanisms. In one you "resurface" the silver with other chemicals, this is the case of selenium and suilfide toners. They deposit a layer that binds with the silver to create a surface "coat." This "coat" under normal circumstances has a treshold level of light that it can absorb (specially UV light) once you overcome that treshold things deteriorate very rapidly because of the formation of free radicals that "eats away" the selenium/sulfide layer as well as the silver. When you bombard a print with very high levels of light you are in fact overcomeing this treshold that might happen otherwise.

The second mechanism is silver replacement. Metals like Platinum, Palladium, Gold have the ability to replace the silver in the print. Being that they are noble metals and have a high stability the energy required to oxidize them as well as their resistance to free radicals is very high. Even so, if you bombard them with high intensity lights you might still overcome this treshold when the chances of this ocurring normally are not likely. Once you overcome this treshold and specially start the formation of free radicals, things go to pot.

Now lets move on to ink jet posters. Organic materials are very suceptible to free radicals. This is the reason why we use SPF blockers and why you guys are in search of a coatings for your prints. In a sterile environment such as a lab, there are few free radical generating agents. So now we have a two fold problem. One, are you overcoming the treshold level that carbon pigments can support? and two is the absence of free radical generating agents important? In a house hold there are many products capable of generating free radicals by the action of UV light. Bleach, Ammonia, cloroflurocarbons, etc, etc. Apparently ink jet pigments are somewhat stable to the action of UV radiation alone (although much lower than metals), it takes some time to degrade, but is it the same case when a free radical generating agent is present? I suspect this is not the case, and the reason why Wilhelm's tests have been wrong many times. As long as Wilhelm keeps reporting results without taking into account probable chemical interactions in the enviroment, I have a hard time accepting his results as valid.

[paulr]

"I'm having a hard time following this statement. Even if the sulfer can displace 100% of the selenium, that does not mean that selenium offers NO protection under normal conditions."

What I assume people are looking for is a significant degree of protection against oxidation and sulfide staining. What's significant is going to be subjective, so I'm using "noticeable" as a standard. Does a selenium toned print stain less? Does it stain more slowly? Not in any way I can notice. It does stain a different color. Maybe you'll like the color more

I don't remember what Wilhelm's specific findings were. But they were disappointing.

Incidentally, the idea that selenium will protect a silver print is based on a simple assumption: that the silver-selenium compound (whatever it is ... silver selenide??) will be more stable than metalic silver. I haven't seen any demonstrations of this ... just assumptions based on common sense. People assume that since silver isn't completely stable, a compound of silver and something else will be more stable. But it isn't always true. Stability is relative. Pure silver is more stable than some silver compounds, less stable than others, and in some cases, it will likely depend on the specific oxidizing agent.

As far as the legal stuff, what is their specific claim? I think it's odd to trust a statement just because it's from Kodak. I find manufacturers have been a less than trustworthy source of all kinds of information in the past.

[Oren Grad]

Per Ctein's tests, we know that selenium does have a clear and dramatic protective effect on RC prints (as does Agfa Sistan). How long the effect lasts is an open question. Also, it's not clear whether his results generalize to FB; it's conceivable that selenium disproportionately inhibits the specific light-driven reactions that are a characteristic failure mode of the PE-coated papers.

[Aaron van de Sande]

Incidentally, the idea that selenium will protect a silver print is based on a simple assumption: that the silver-selenium compound (whatever it is ... silver selenide??) will be more stable than metalic silver. I haven't seen any demonstrations of this ... just assumptions based on common sense. People assume that since silver isn't completely stable, a compound of silver and something else will be more stable. But it isn't always true. Stability is relative. Pure silver is more stable than some silver compounds, less stable than others, and in some cases, it will likely depend on the specific oxidizing agent.

The heat of reaction will give you a pretty good idea of how stable it is. I am sure that silver selenide is at a lower state than elemental silver. The sulfide is at an even lower state. If you look at the periodic table you will see that oxygen, sulfur, and selenium are all in the same column, so they have similar valience electrons (and form similar compounds)

The oxide is at the lowest state but it doesn't have properties that are good for a negative or print.

[Aaron van de Sande]

Actually I cannot think of any reason why the oxide would be any less desirable in a print or negative. Silver oxide is black. Perhaps we can tone with just hydrogen peroxide?

[Kirk Gittings]

"one more thing ... I urge caution if you plan to experiment with anything stronger than 1:8. I have had negs wrecked by selenium solutions that were too strong. as always, YMMV ..."

I haven't found this to be true. Selenium toning on negatives only goes to completion-about a one zone increase in highlight desity. After much testing, I have been using straight toner for twenty years now. It simply does it faster with absolutely no discernable difference to a slow dilluted tone.

[kthompson]

i don't why I bothered to link to those sites above, but here's another one:

http://www.iaq.dk/papers/iada1999.htm

[Jorge Gasteazoro]

i don't why I bothered to link to those sites above, but here's another one:

I think they are useful, if anything so that people understand that light fastness tests that exclude atmospheric poullutants are misleading. The last 3 links from your previous posts seem to be opinions, albeit by someone who seems knowledgeable in the subject. But the first one and the link you just posted are very good articles IMO. Thanks for "bothering"... :-)

[paulr]

Here are some excerpts from a study by the Image Permanence Institute at RIT.

The good news: selenium toning can improve resistance to oxidation if 100% of the silver is converted to silver selenide. In other words, extreme toning, which you might be able to achieve if you're trying to intensify your negs (although the only negative developing disasters that I've personally had come from trying to do this ... be careful). They also conclude that sulfide toners, particularly those using polysulfides, provide the best protection. The tests were focussed on archiving microfilm.

Interestingly, Aaron, the paper addresses your peroxide question. Apparently peroxide has been traditionally used to test image permanence because of its ability to stain. These researches used various forms of peroxide to conduct all their trials.

"The results of the IPI research led to four main conclusions:

Excellent protection against peroxide attack can be gained by treating microfilm with solutions which lead to the partial sulfiding of the silver image. The best compounds to use, as well as methods of application and possible ill effects on physical properties, etc., are unknown at this point, but there are several promising candidates (in particular, polysulfides), and the direction to be pursued is now clearly established.
Geld and selenium treatments provide protection against peroxide attack only in proportion to the degree to which the heavy metal is substituted for the original silver image. In the absence of sulfiding agents, even very high degrees of gold or selenium substitution do not provide complete protection. In actual practice, when used as recommended, the metal components of gold and selenium toners for microfilm do very little to protect against oxidation; their effectiveness is almost entirely due to the sulfiding action of other constituents of the toner formulas.
Washing of microfilm to extremely low levels of residual thiosulfate, which is regarded as good archival practice, in fact causes film to be substantially more susceptible to peroxide attack than if the washing were less effective. Some form of treatment to protect against oxidation is essential to achieve maximum longevity for microfilm produced with contemporary processing machinery.
As has been reported by others (19), residual thiosulfate can actually stabilize a silver image against oxidation, if present in the right concentration. However, it is impossible in practice to control the concentration by manipulating washing variables. To achieve a reliable degree of protection, film should be well washed, them treated in a controlled fashion with some form of stabilizing bath."

"The peroxide tests at IPI showed that Kodak Rapid Selenium Toner failed to provide protection against redox blemishes, when used as suggested. If highly concentrated solutions were used, the level of protection increased, but was not complete. Such concentrated solutions are impractical for reasons of cost, excessive contrast buildup, and excessive image color change, even if they did provide enough protection. This finding conflicted with numerous published results from Kodak (17,20,21); when we spoke with Kodak personnel, they confirmed that in their own recent peroxide testing with microfilm, the selenium toner was depositing selenium, but not preventing oxidant attack, which it had done in tests performed as recently as one year ago. They suspected that small changes in formulation made by the manufacturing area were responsible, but were not clear on exactly why.

It is our strong feeling that the changes in formulation that suddenly rendered dilute selenium toner ineffective relate to the sulfiding action of minor constituents. Although the formula for Kodak Rapid Selenium Toner is proprietary, it is known to contain both sodium sulfite and hypo (sodium thiosulfate), both of which may be contaminated with small amounts of highly active sulfiding agents. Apparently insignificant manufacturing changes may have caused this active agent to be no longer present; it would still form silver selenide and achieve a toning action (in the sense of color change), but would no longer protect against peroxide. In any case, the surprising ineffectiveness of Kodak Rapid Selenium Toner, together with many other signs of the potency of sulfiding agents, pointed the way to a much different analysis of image stability and how to achieve practical protection against red spots.

One of the strongest clues to the power of sulfiding agents to protect against peroxide came from experiments with gold tuners. Kodak has recommended a formula known as GP-2 since the 1960s for the treatment of microfilm to prevent red spot attack (7,14). Because of the high cost it has seldom been used in practice, but it was always regarded as absolute protection. One of the ingredients of GP-2 is thiourea, a known sulfiding agent. In experiments at IPI, this formula was indeed completely effective in preventing peroxide attack. However, experiments with the same formula without the gold were completely effective. In both the gold toner and the selenium toner, it seemed to be the sulfiding agents, not substitution with gold or conversion to silver selenide, that was providing the bulk of the protection against oxidants.

This was confirmed in another series of experiments where gold and selenium formulas which did not contain a sulfiding agent were used. They "toned," in the sense of depositing gold or converting the silver to silver selenide, but the protection against peroxide was only in proportion to the degree of substitution. Even virtually complete conversion of the silver image to gold did not stop peroxide attack; the small amount of remaining silver discolored in the peroxide test."

full text:
http://palimpsest.stanford.edu/byorg/abbey/an/an12/an12-5/an12-507.html

[paulr]

"I haven't found this to be true. Selenium toning on negatives only goes to completion-about a one zone increase in highlight desity. After much testing, I have been using straight toner for twenty years now. It simply does it faster with absolutely no discernable difference to a slow dilluted tone."

I'm glad to hear this works ... I have no idea why I had such problems with strong dilutions. Possibly I made some other mistake. At any rate, I didn't want to repeat the process to find out. And the problems never showed up at 1:8, so I kept doing that. I just want to encourage anyone experimenting with stronger concentrations to be careful.