[Alt-photo] Sodium Thiocyanate For Fixing Out Lumens

Marek Matusz marekmatusz at hotmail.com
Thu Aug 17 18:02:32 UTC 2017


I would be very interested in the two articles on the chemistry of fixing. Could somebody share a copy?
Marek

Sent from my iPhone

> On Aug 15, 2017, at 12:51 PM, Ryuji Suzuki via Alt-photo-process-list <alt-photo-process-list at lists.altphotolist.org> wrote:
> 
> You might want to get a copy of this paper if you like to see what's known in situations that are somewhat close to what you are doing. Without chemical development process you don't have filaments but you can probably learn from what happens to the smallest grain, thinnest filament condition among what he studied. Abstract is from uncorrected OCR, sorry about some errors.
> 
> The Stability of Silver Filaments
> T. H. JAMES, Research Laboratories, Eastman Kodak Company, Roch:ester, N. Y. 14650
> 
> PHOTOGRAPHIC SCIENCE AND ENGINEERING Volume 9, Number 2, March-April 1965
> 
> The effeds on the strudure of the developed silver of storage at high' humidity and of treatment with various salt solutions were studied on several bromide emulsions. An over-all increase iii transmission density, with some decrease in refledion density, occurred with fine-grain emulsions within a few hours upon storage at approximately 100% relative humidity at 21°C. Similar changes occurred more rapidly at higher temperatures. 'The changes were more pronounced with unfixed, fully developed film than with fixed film, and the changes in density wete accom- panied by a thickening and breaking up of the filamentary strudure and an increase in crystal- lite size. Similar changes in filament strudure, and a decrease in refledion density, occurred for all chloride, chlorobromide, arid bromide emulsions tested, but IiHle or no change in trans- mission density was observed when the original silver halide grain size exceeded about 0.4 ",. Iodide, whether derived from the processing solutions or from the development or fixation of the silver halide grains, retarded the changes. A rapid conversion of filaments into nonfilamentary, rounded particles occurred in the chloride, chlorobr9mide, and bromide emulsions when the unflxed, developed film was immersed in a 1%or stronger.solution of a thiocyanate or chloride. The degradation of the fllaments was retarded by iodide and thiosulfate, by the presence of strong reducing agents, or by stringent exclusion of oxygen, but it did occur readily under the
> laHer condition when silver ions were added to the solution. The degradation of the fllaments appeared to be a recrystallization phenomenon, and a mechanism based on local cell action was suggested.
> 
> 
> Regarding the fixing mechanism of sodium v ammonium thiosulfate, and thiocyanate, see
> 
> The chemistry of fixing I. Silver complexation by thiosulfate anion
> M.R.V. Sahyun, Imaging Research Laboratory, 3M Company, St. Paul, Minnesota 55101
> PHOTOGRAPHIC SCIENCE AND ENGINEERING· Volume 17. Number 2. March/April 1973 Reprint Number 7326
> 
> The chemistry of fixing II. Silver complexation by thiocyanate anion
> M.R.V. Sahyun, Imaging Research Laboratory, 3M Company, St. Paul, Minnesota 55101
> PHOTOGRAPHIC SCIENCE AND ENGINEERING. Volume 17. Number 2. March/April 1973 Reprint Number 7327
> 
> Chapter 5 of James's 1977 book is also an excellent reference. (The chapter written by R. W. Henn)
> 
> Finally, be careful about thiocyanate as a fixing agent. As James's paper shows, it can change the morphology of the silver image, and you want to control the residue very carefully. Also, strong thiocyanate solution damages gelatin and weakens the mechanical properties and perhaps long term durability. I think it is probably wise to formulate a fixing solution that is primarily based on thiosulfate but uses a pre-bath or an additive to alter the image tone as desired. The topic of image tone was a very common one for the radiographic film emulsions and their developer formulation. Very numerous patents issued, with very many compounds named (but in reality, I bet only a few used in practice).
> 
> Ryuji Suzuki
> "Don't play what's there, play what's not there" (Miles Davis)
> 
>> On 14 Aug 2017, at 14:00, Andy Duncan via Alt-photo-process-list wrote:
>> 
>> Hi all,
>> 
>> I’m experimenting with different ways of fixing lumen prints, and read
>> somewhere (I think in a thread on apug.org) that sodium thiocyanate can be
>> used to fix out prints. I've used Ilford Rapid Fix in the past, but my main
>> fixer in recent years has been TF-4 from Photo Formulary, which is what I
>> use for my film. The color shifts from both were pretty similar, both being
>> ammonium thiosulfate. I began using the sodium thiocyanate recently, and
>> after my last batch of prints, I noticed that after processing, some of the
>> prints continued to darken. I processed in a 5% dilution for 1-2 minutes (I
>> don't get real scientifically accurate with my times when processing
>> lumens...maybe that's part of my problem); the source I first read that
>> mentioned using sodium thiocyanate gave a 10% dilution. So my question is
>> this: is sodium thiocyanate as permanent of a fixer as the other fixing
>> agents in TF-4 and Ilford Rapid Fix?
>> 
>> I was also wondering if any of the chemists out there could explain in
>> layman's terms the difference between sodium thiocyanate and ammonium
>> thiosulfate? What is the effect each has on image permanence and
>> stabilization?
>> 
>> I suppose I should add that I'm not afraid of the color shifts that occur
>> after fixing a lumen print, nor are they unwanted. On the contrary, I tend
>> to welcome them. I just want the lumen to be as permanent as I can make it.
>> I'm starting to prefer the shifts that occur with the sodium thiocyanate
>> over those that occur with TF-4, so I'd like to make sure they'll be as
>> stable when processed in TF-4. I have prints that are 10+ years old that
>> have had no further shift in color/intensity/brightness after being hung on
>> my walls. These recent ones shifted only hours after being taken off my
>> drying racks.
>> 
>> Thanks in advance!
>> Andy
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