Polysulfide toners
Frank Earl
several things:
1) Is there a cheap source of solid sulfurated potash? Perhaps fertilizer
grade?
2) The "new" Viradon formula from Agfa indicates that they use 10% Na
sulfide to stop toning during wash. I realize that polysulfide toners tone
faster as they dilute. Does anyone know experientially if this works?
3) Do the microfilm archivists still say that the only way to achieve image
stability is through use of a polysulfide toner such as Kodak Brown toner or
the IPI SilverLock Toner?
4) If 3 is true is there any additive to the polysulfide toners that will
provide different coloration?
5) There are websites, primarily relating to microfilm that indicate the
only reason Kodak-type selenium toner and Kodak-type gold toner provided
image stability was because of some sulfur in the toner. When that was
removed through manufacturing improvements the image stability was no longer
guaranteed. This research is about 10 years old. Is this still the case?
I am able to test out #2 above myself but image stability is rather
difficult to test out at home in your spare time.
Thanks for any information or opinions.
Richard Knoppow
I'll try to answer as much of this as I can.
1, I don't know of a cheap source of liver of sulfur. The qulity of
the product is important to the quality of the toner.
2, Viradon and Kodak Polytoner are combination toners consisting of
polysulfide and selenium. The "stop bath" works for both and for other
polysulfide toners like T-8 and Brown Toner.
Since polysulfide toners have the curious property of toning faster
as they becme diluted or exhausted its important to wash out the toner
as quickly as possible at the beginning of the wash. It not washed out
it can leave a peach colored stain in the highlights which is
permanent.
The reason for the increased toning effect is probably due to the
rank of the sulfur anions in the molecule. The rank tends to increase
with concentration. For this reason also the method of preparing a
polysulfide toner is important as I will discuss below.
The paper you are refering to is one published by Reilly, Nishimura,
et.al. of the Image Permanence Institute (IPI) and appearing in the
Abbey Newsletter (1). This paper refers to research done about ten
years ago for the National Endowment for the Humanities. The complete
report is available from the IPI (2). The NIH discovered microfilm
which had been processed and treated in the manner prescribed was
showing sighs of image degradation, particularly redox spots, this
despite toning in Kodak Rapid Selenium Toner.
The original research on toner treatment was reported in a paper
from Kodak Research Laboratories (3) by Lee, Wood, and Drago. These
researchers investigated the effects of toning in Kodak Rapid Selenium
Toner, Kodak PolyToner, an iron - ferricyanide toner, and a copper -
ferricyanide toner. The results showed that treatment with KRST
diluted to 1:20 provided substantially complete image protection with
little change in image structure or color. PolyToner also provided
protection but with greater change to the crystaline structure of the
image. Both ferricyanide toners resulted in images less stable than
untreated silver.
The Abbey Newsletter summary of the NIH research reports that IPI
discovered that the KRST used to tone the microfilm at NIH was not
acting effectively on low density areas of the image allowing
oxidation of the image. Redox spots are very small areas where the
silver has been oxidized to silver oxide and has migrated to be
reduced again to metallic silver by other polutants. The action is due
mainly to atmospheric polutants, particularly peroxides.
No one know for certain why the KRST stopped working. It is
speculated that there was some impurity in one of the components of
the toner which provided the protection, probably through some amount
of sulfiding. However, Kodak claimed that no change had been made in
the formula of the toner. The most likely cause was a change in
suppliers of some component or a change in the method of manufacture
of that component.
In any case, diluted KRST is not able to provide complete protection
to microfilm and may have similar difficulties with other very fine
grain emulsions such as that on printing paper. However, printing
paper per se was not investigated.
The same IPI research found that at least part of the protecton
provided by Koak GP-2 Gold Protective Solution was due to incidental
sulfiding. The Abbey Newsletter report is misleading in saying that
the solution provided as much protection without the gold chloried as
with it. The sulfiding is not even and the Gold does play a part in
providing image protection. This toner works _providing toning is
carried out far enough_. This last statement is very important since
it also applies to KRST.
IPI's research on this issue was to find a toner which would provide
complete protection to microfilm but cause too much change to image
structure, color, or density. The answer was a modified polysulfide
toner called by IPI Silverlock. This toner is similar to Kodak Brown
Toner but is made with Borax rather than sodium carbonate.
Since the ability of the toner to tone all densities evenly depends
on its molecular complexity the stock solution needs to mixed at a
considerable concentration. While the formula for Silverlock is simple
the method of compounding must be followed carefully. The use of Borax
has several advantages, not least of which is low odor.
Keep in mind that Silverlock was designed for the protection of
microfilm and may not be satisfactory as a paper toner.
Kodak Brown Toner, diluted 1:25 provides substantial protection but
will cause some change to image color.
KRST will provide complete protection if toning is carried out long
enough. Dr. Douglas Nishimura of IPI recommends using it diluted no
more than 1:9 and for at least three minutes at that dilution (4)
The older Kodak Gold formula GP-1 is similar in that it will provide
image protection provided toning is carried out to where a substantial
proportion of the silver is converted.
The ratio for microfilm is 65% convertion of silver for IPI
Silverlock and probably thats a good precentage for other toners.
The amount of toning of Selenium, Sulfide, or Gold can be determined
by bleaching the image in a bichromate bleach to remove the silver,
clearing the stain and measuring the density of the remaining image
with a densitometer with appropriate color filtering. There should be
a substantial toner image in all densities of the image.
Film or paper to be toned in Polysulfide toner should be treated in
an alkaline bath or in Kodak Hypo Clearing Agent and well washed
before toning since any acid carried over from the fixing bath will
tend to decompose the toner. Washing shoud be rapid, as pointed out
above because decomposition fo the toner in the wash as it becomes
diluted will result in increased toning and staining. The Agfa
recommendation of using a 10% sulfide bath before washing will help
alleviate this.
Toning to completion in any sulfide, selenium, or gold toner will
provide a very high level of image protection, however, with
consequent change in structure, color, or density of the image.
1, "Stability of Black-and -White Photographic Images, with Special
Reference to Microfilm" James M. Reilly, et.al. _Abbey Newsletter_
Vol. 12, No. 5, July 1988
Available from the Conservation On Line site at:
http://palimpsest.stanford.edu An author search for Reilly or
Nishimura will find it.
2, _Final Report to the Office of Preservation National Endowment for
the Humanities_ Grant # PS-20152-87, "Sulfiding for Protection for
Silver Images", March 28, 1991, James M. Reilly, Kaspars M. Cupriks,
Available from the Image Permanence Institute, Rochester Instute of
Technology.
3, "Toner Treatments for Photographic Images to Enhance Image
Stability" W.E.Lee, Beverly Wood, and F.J.Drago (Of Kodak Research
Laboratories) _Journal of Imaging Technology_ Volume 10, Number 3,
June 1984
4, Personal communication from Dr. Nishimura.
Also, some months ago Dr. Nishimura very kindly posted a great deal
of material to this news group. It should be recoverable from Google
by searching for the author, Douglas Nishimura.
Dr. Nishimura has also contributed a number of articles and letters
which are archived on the Conservation On Line Site and can be found
with an author search.
I hope this is helpful. I have on the back burner an article
summarizing all I have found out about processing for permanence but
must pass the material before Doug before posting it. Its an area of
great confusion. Part of the trouble is determining how much of what
applies to microfilm also applies to more general purpose photographic
material.
Also be aware that a small residue of thiosulfate in the emulsion
acts as a stabilizer to excessive washing ironically results in less
rather than more permanent images, according to Lee, Wood, and Drago,
even when the images are toned.
---
Richard Knoppow
Los Angeles, Ca.
dick...@ix.netcom.com
Francis A. Miniter
archives. Please do move the article from the back burner a bit forward!
Francis A. Miniter
Thomas Wollstein
> 2) The "new" Viradon formula from Agfa indicates that they use 10% Na
> sulfide to stop toning during wash. I realize that polysulfide toners tone
> faster as they dilute. Does anyone know experientially if this works?
The stop bath for Viradon is sulfite, not sulfide!
As far as I know, Viradon is a combined selenium and polysulfide toner.
Regards,
Thomas Wollstein
wjjk
Na-sulfite solution, the color turns green. My guess is that Viradon contains
dichromate as a bleach (has a very clear orange color). Sulfite reacts with
dichromate to form chromiun(III) ions which are green and have no bleaching
power.
Walter
Bill Troop
> I hope this is helpful. I have on the back burner an article
> summarizing all I have found out about processing for permanence but
> must pass the material before Doug before posting it. Its an area of
> great confusion. Part of the trouble is determining how much of what
> applies to microfilm also applies to more general purpose photographic
> material.
Richard, thanks for a great summary of present knowledge on this difficult issue;
I eagerly await your finished article. Here's my request. I see two problems
here: (a) the microfilm research is already a little old and (b) we have no idea
to what extent we can extrapolate microfilm results to prints. That being the
case, I would ask if you could publish a precise, step-by-step methodology for
testing films and prints? Even if it is impractical for anyone to do the work
right now, having the methodology published would be an enormous step forward.
> Also be aware that a small residue of thiosulfate in the emulsion
> acts as a stabilizer
That 1984 bombshell seems still to be unexplored. Can anyone now suggest how to
quantify the ideal amount of residue? Who knows? Now that Bill Gates has
developed an interest in photographic preservation, and has hired Henry Wilhelm,
maybe we'll see some new research?
Mark Rabiner
><Snip> the ideal amount of residue? Who knows? Now that Bill Gates has
> developed an interest in photographic preservation, and has hired Henry Wilhelm,
> maybe we'll see some new research?
HypoClear for Windows?
Archival Office?
Mark Rabiner
Portland, Oregon
USA