Is selenium toner concentrate always good? I have the same kodak glass bottle since the years 1980, I think!!!
I use selenium a low dilution for print permanence, not really to tone. Any difference between differents brands now on the market. Are they the same formulary and produce the same print color (at low dilution)?
All the research shows that selenium toner has no practical effect on print permanence, unless the print is toned all the way (to the point where it won't take on any more selenium). Which isn't what very many people do. I can share the info if anyone is still unfamiliar with it. At any rate, there's no reason to use the stuff except for esthetic reasons. The concentrate lasts a long time. No idea if it lasts 30 years though ...
Thanks Paul, I will appreciated if you recommand me some readings about.
If I find a good link I'll post it. Meanwhile, here's some correspondence from a researcher at the Image Permanence Lab at RIT. His research was about microfilm, but he mentions that his finders were the same as other groups studying gelatin silver paper:
I suspect that in part, your question is in
regard to work that we did here at the Image Permanence Institute back in
the late 1980's and early 1990's. We were working on a project funded by
the National Endowment for the Humanities to look at the use of selenium
toner to improve the stability of silver-gelatin microfilm.
Historically, there were a number of classic papers written on the topic
starting in the the early 1960s with regard to gold toning (there is a
connect that we'll get to later.)
1965. Henn, R. W.; Wiest, D. G.; Mack, B. D. "Microscopic Spots in
Processed Microfilm: the Effect of Iodide." Photographic Science and
Engineering. 9(3):167-173.
While iodide is not toning, it is an important article with regard to
the science of toning and permanence.
1965. Henn, R. W.; Mack, B. C. "A Gold Protective Treatment for
Microfilm." Photographic Science and Engineering. 9(6): 378-384.
1966. Henn, R. W.; Wiest, D. G. "Properties of Gold-Treated Microfilm
Images." Photographic Science and Engineering. 10(1): 15-22.
1984. Lee, W. E.; Wood, B.; Drago, F. J. "Toner treatments for
photographic Images to Enghance Image Stability." Journal of Imaging
Technology, 10(3): 119-126.
1984. Brandt, E. S. "Mechanistic studies of Silver Image Stability. 1:
Redox Chemistry of Oxygen and Hydrogen Peroxide at Clean and at
Adsorbate-Covered Silver Electrodes." Photographic Science and
Engineering, 28(1): 1-12.
1984. Brandt, E. S. "Mechanistic Studies of Silver Image Stability. 2:
Iodide Adsorption on Silver in the Presence of Thiosulfate and the
Influence of Adsorbed Iodide on the Catalytic Properties of Silver
Toward Hydrogen Peroxide." Photographic Science and Engineering,
28(1):13-19.
1987. Brandt, E. S. "Mechanistic Studies of Image Stability. 3.
"Oxidation of Silver from the Vantage Point of Corrosion Theory."
Journal of Imaging Science 31(5): 199-207.
The first problem is the question of what the primary cause of
instability in silver. Because many photographers were intentionally not
washing well or were messing with the fixing bath when processing
albumen prints, everyone hears that bad processing is the root of all
deterioration. For the albumen people, they initially got a very neutral
looking photograph because the sulfur ions adsorbed to the colloidal
silver image particles drove the absorption peak for the colloidal
silver from the violet region down to the green part of the spectrum.
The effect is pleasant for a short time and if you only have albumen (or
other POP process from which to make prints) and you really want a
neutral black and white image (such as we got with the modern
silver-gelatin DOP) then adding sulfur to the colloidal silver image did
the trick. However, the large excess of sulfur present had consequences
and as the colloidal silver turned into colloidal silver sulfide, the
absorption peak dropped in to the UV region (causing the image to turn
to a pale yellow). The drop in optical density combined with the eye's
general lack of sensitivity to yellow caused albumen prints to all but
disappear completely. The interesting thing is the fading committee
report included problems such as air pollutants, bad adhesives, and high
humidity (all of which result in the oxidation of silver rather than
sulfiding.) All of this issues were ignored and people only focussed on
the poor processing. Hence, every photographer hears that bad processing
is problem. You will find that finding examples of poor processing are
not so easy to find. In fact, the major cause of deterioration is
oxidation. As Fuji described it in 1982, the deterioration process is
rather cyclic. The image silver particle is exposed to oxidant which
causes silver ions to break away from the image particle. These silver
ions are mobile and migrate through the emulsion with spherical symmetry
(no preferred direction of movement.) The ions may run into something
like a sulfur source or halide source and precipitate in the emulsion as
an insoluble, immobile particle of a silver compound (a dead end event
removing that silver ion from the rest of the system.) The silver ion
may find an electron source and reduce back into a particle of colloidal
silver. The colloidal silver may appear as silver mirroring (if it
happens to reduce back to metallic silver at the surface of the
emulsion), as orange, red, or yellow colloidal silver (most obvious in
the midtones and highlights), or coallesce as a redox blemish (also
known as measles, red spots, or microspots.) When I worked for Klaus
Hendriks, we could see that no matter how cross-sections were cut in
deteriorated photographs, the result was always a circular halo of
colloidal silver particles around the former image particle, thus
demonstrating that silver migration has no preferred direction and is
spherically symmetrical. In relation to the Fuji work, is another
surprise for most people. Fuji found that a small amount of residual
fixer in their samples actually made them more resistant to oxidative
attack. They weren't the first people to discover this. George Eaton
told us that back in the 1960s, they found the same thing at Kodak, but
didn't know how to tell people to wash well, but not too well. As a
result, they only told people about washing well (since failure to do so
would directly result in damage to the photograph; whereas "over"
washing would only cause trouble if the silver was exposed to oxidants
(which really were everywhere anyway.) In hind-sight I agree with their
decision. We observed the same effect in 1987 as has Ilford and Agfa. So
the primary purpose of toning for permanence is to prevent oxidation.
There is nothing magic about microfilm silver (except that it tends to
be very fine grained), but the chemistry that governs what happens to
microfilm silver, also applies to paper (and we'll get into that later.)
Microfilm was the first photographic material considered to have enough
value that its deterioration warranted reseach funding and interest. One
thing that was observed with microfilm was that older fixer (so called,
"seasoned" fixer) resulted in more stable film than film processed in
new fresh fixer. It was determined the iodide in the fixer (that was
coming out of the fixed film) was producing the higher stability so
microfilm fixers were sold with potassium iodide added. Why the iodide
was helping the stability of the film was not answered until Steve
Brandt's papers in the 1980s. He pointed out that hydrogen peroxide (a
very common atmospheric oxidant found in storage and display
environments) was catalytically decomposed on the surface of silver.
During the process, the peroxide acts as both an oxidizing agent and
reducing agent causing the silver to oxidize and later reduce back to
metallic silver. (Migrating in between.) Brandt found that adsorbed
iodide ions on the silver surface poisoned the surface as a catalyst and
prevented the decomposition of the peroxide. Thermodynamically, iodide
and silver have a stronger drive towards forming silver iodide than pure
silver does to forming silver ion. (The Gibbs free energy change for the
have cell reactions are -14.69 kJ per K per mole and +77.16 kJ per K per
mole. Thermodynamics says that the Gibbs free energy must decrease for
spontaneous reactions (the change must be negative.) However, although
the oxidation of silver and iodide to silver iodide is thermodynamically
preferred, it is kinetically very very slow-- slow enough that chemists
call the system stable. Thermodynamics tells us which direction
reactions go (and why we can readily change high octane gasoline and
oxygen quite readily into carbon dioxide and water, but can't convert
carbon dioxide and water into high octane gasoline and oxygen very
easily.) Given enough time, silver with adsorbed iodide ions will change
into silver iodide, but kinetics tells us that it will be a very long
and slow process. In theory, sulfide ions should do the same thing, but
Brandt had a feeling that sulfide ions were less stable as ions than
iodide ions were so he recommended iodide over sulfide. Selenium and
sulfur are both in the same family and should have similar chemistries,
although selenium is one period lower on the table and it has d-orbitals
that allow it a wider range of possible oxidation states.)
[continued ...]
....
Lee, Wood, and Drago published the first paper dealing with the
stability properties of a variety of toned images (including selenium.)
They found that selenium acted very well as a protective treatment and
in theory we would've (and did) guess that that would be the case. If
sulfur works, so should selenium. When we studied selenium toning for
the preservation of microfilm, we found that selenium worked pretty well
for high density areas (shadows), but failed in the highlights and
mid-tones (where we tend to see colloidal silver formation.) It
apparently just doesn't convert the mid-tones and highlights all that
well. When we brought this to Kodak, they tried to dig back in their
records for formulations and chemical sources. They had run into
something similar with regard to stabilization processed photographs.
Prints produced by users in the field had unusually stable prints (quite
resistant to oxidants), but when they tested the processors in the lab,
they didn't find any high level of resistance to oxidants. It drove them
crazy for some time before they realized that they weren't using the
same chemicals in each test. If they used the chemicals that consumers
were using, then they found the high level of stability. The difference
was that consumers were using processing chemicals made from what a
chemist would call practical grade chemicals (Kodak referred to "tank
car quality" while experiments in the lab were being done using
analytical reagent grade chemicals (very high purity.) It turned out
that the sodium thiocyanate made from practical grade chemicals was
contaminated with a number of active sulfur compounds while the high
purity analytical grade chemicals weren't. Photographic chemists
distinguish sulfur compounds that contain sulfur with different
oxidation numbers. "Active" sulfur compounds contain sulfur atoms with
an oxidation number of -2. All other sulfur compounds are inactive. For
us, the two main rules are that oxygen always has an oxidation number of
-2 and one must maintain the charge on the entire radical species. So
sulfite ion has a total charge of -2. It has 1 sulfur and 3 oxygens.
Each oxygen has an oxidation number of -2 (for a total of -6). Since the
entire sulfite radical (or ion) has a charge of -2, then the sulfur must
have an oxidation number of +4. Similarly, with sulfate ion, the sulfur
has an oxidation number of +6. So neither sulfite nor sulfate are active
species. Soaking film or prints in either sulfite or sulfate does not
impart any degree of stability, nor if left long enough, will the silver
image sulfide. If we follow the rules for oxidation number with
thiourea, we find that the lone sulfur in this compound has an oxidation
number of -2 so thiourea is active and we found that thiourea solutions
could sulfide silver and impart a certain degree of stability to silver
images. The sulfur in thiocyanate is not -2 so thiocyanate is not
active. Selenium toner can be made by combining selenium with sodium
sulfide to make sodium selenosulfide. The other way to do it is to
combine selenium with sodium sulfite to produce sodium slenosulfate.
Effectively sulfur combined with sodium sulfite makes sodium thiosulfate
which is why fixer is stabilized by additing sodium sulfite. The excess
sulfite tends to minimize the decomposition of thiosulfate to sulfite
and sulfur. It was possible that selenium toner tested by Bard et al was
an old bottle possibly contaminated with active sulfur compounds.
However, we obtained a bottle of selenium toner from the same
approximate time and tested it and got no better results.
Kodak tried similar tests out and also found that the selenium wasn't
working as well as it apparently did in the early 1980s and no one
understands why.
However, we did find it interesting that the long-known solution of gold
chloride and sodium thiocyanate (known as Kodak GP-1) worked pretty
well. It lays down a pretty even amount of gold all over and if you
remove all of the remaining silver, you're left with a very low density
image made of gold. Henn and Mack, in the 1960s worked on a better
formula that was to become known as GP-2. It consisted primarily of gold
chloride and thiourea with a few other salts added. This formula really
worked well on films and prints. Henn and Mack observed that as they
increased the gold content of the solution, they observed no increase in
the "protectiveness" of the solution, but as they increased the thiourea
content, the treated film stability went way up. They didn't pursue the
problem and simply decided to use five times as much thiourea as gold.
So here we have pretty strong evidence that the thiourea complexing
agent (that kept gold from falling out of solution) was contributing to
the stabilizing effect of the toner. Gold solutions not containing
active sulfur (such as GP-1) had no such effect if we varied the
concentration of the complexing agent. Interesting.
Combine this observation with the observation that a small amount of
residual thiosulfate (hypo) is good for the stability of silver
photographs and you're forced to draw some conclusions about sulfur.
Thiosulfate has two sulfur atoms, one with an oxidation number of +6 and
the other with an oxidation number of -2 so thiosulfate is an active
sulfur compound. Just a tiny amount of sulfur "dusted" on the surface of
silver image particles can make the silver fairly stable against
hydrogen peroxide oxidation, but for things like ozone and nitrogen
oxides, actual conversion to silver sulfide is required. Selenium will
work, but a heavier dose of toner is required in order to ensure that
the mid-tones and high-lights are adequately protected.
How about papers? Back in 1992 we had a Swiss Graduate student here
doing his MFA here. The title of his thesis was On Black-And-White Paper
Image-Stability Enhancement: Effectivenss of Toning Treatments on Silver
Gelatin Prints Determined by the Hydrogen Peroxide Fuming Test. This
411-page thesis reached the same conclusions that we had regarding
toners with film. If you search for the thesis through the library, the
author is Christopher Gmuender.
-Doug
Douglas W. Nishimura
Senior Research Scientist
Image Permanence Institute
Rochester Institute of Technology
I know that's a grunt to get through. I posted in its entirety so as not to inadvertently delete interesting bits.
The two most interesting upshots I see are that sulfides are much more effective than selenium or gold, and that incomplete fixer removal is actually beneficial (and that Kodak's known this a long time, but it's just too complicated to try to explain to consumers).
And it suggests that back in the 90s when I used reagent grade chemicals and washed prints for hours, I was being dumb, not fancy.
What Paul said. More information here:
http://www.largeformatphotography.in...erimental-data
http://www.largeformatphotography.in...and-Permanence
There's likely some worthwhile benefit from light toning of RC, because it at least partially squelches a failure mode that's distinctive to RC paper. But if you're printing on FB, it's probably not worth the substantial extra time, water and labor unless you want the visual effect for esthetic reasons.
Thanks to both. My intention is to restart darkroom printing and I will probably buy Ilford Warmtone so I will see what will be the tint with and without selenium.
I will test my old bottle before ordering new one. In one of the topics, they talk about an old bach of selenium from the 80s ....
ah ahOriginally Posted by paulr
maybe it is my batch!
Maybe I will stop using selenium and doing excessive washing.
Both the RC and FB versions of Ilford Warmtone are very sensitive to selenium, though in different ways. Depending on the concentration and temperature of the toner and the duration of toning, you can get quite a range of different color and density effects.
Happy printing!
I have an Ilford publication entitled "Ilford Multigrade Papers - A Manual for the Darkroom" that includes this statement:
"Optical Brighteners
The optical brighteners that give Multigrade papers their brilliant, sparkling whites stay exactly where they are needed - in the highlight areas of the print. All MULTIGRADE papers, except MULTIGRADE FB WARMTONE, have anchored optical brighteners which means they won't wash out and the paper stays white. With MULTIGRADE FB WARMTONE, the brighteners can be removed with extended washing for an even warmer base tint."
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