Fox Talbot and salt fixing ?

[Gerald C Koch]

I really don't understand why this is important to some people. Salt is not a practical fixing agent. Talbot's early salt prints faded quite rapidly. A few survived and are in a British museum where hey can be viewed only for a brief period under very dim light. They are not fixed in any sense of the word. Fortunately Talbot switched to hypo.

 

[removed account4]

hi gerald

i can see what you mean but i can also see why someone may want to use salt
its the original / authentic way of doing salt prints.. it is finicky and some/most of the time
doesnt' work well .. and it sounds like fun !

 

[pdeeh]

I really don't understand why this is important to some people. Salt is not a practical fixing agent. Talbot's early salt prints faded quite rapidly. A few survived and are in a British museum where hey can be viewed only for a brief period under very dim light. They are not fixed in any sense of the word. Fortunately Talbot switched to hypo.

Gerald, as a chemist, do you not have any curiosity as to the history of your profession?

Is it not interesting to you understand what the processes were that were occurring when the alchemists of the 14th century were experimenting with their peculiar mixtures, and yet achieving something similar to what happens in today's laboratories?

You are after all, someone who frequently admonishes others to do their research before asking a question, and here we are undertaking collaborative research into the history of a photographic chemical process, and yet you admonish us for doing so!

Sometimes, it seems hard to "win" ... or, to put it another way, damned if you do, damned if you don't

 

[Rudeofus]

However, this is very interesting (well, I mean of course, it is interesting to me), because it seems to indicate that while many authors (and "authorities", viz Dr.Mike Ware) refer to Talbot "stabilising" his early prints in salt solutions, that he was actually fixing them, but fixing them incompletely. A photochemist would not call what has been done "stabilising" except perhaps as a loose or conversational term.

There are two conceivable ways to distinguish between fixing and stabilizing:

1. One could call it fixing if silver salts are removed whereas stabilizing would denote conversion into stable silver salts.
2. One could call fixing any process which produces a really permanent image, whereas stabilization would denote any process which would keep the image intact for a few weeks.

Both distinctions have been used ("Using PMT as stabilizer" vs. "how can I stabilize my pic until fresh fixer arrives?"), and it usually becomes clear from context which one is used. Treatment of Silver Chloride in Sodium Chloride would definitely fit into the "fixation" category in the first distinction, and loosely fit into the "stabilization" category in the second distinction.

 

[Alan Johnson]

In my test I found that fixing for extended times in near-saturated salt solution causes the photogenic drawing to go pale yellow.
When redeveloped in Rodinal, after about 1hr fixing the print is still blackened but after 24hrs in near saturated salt solution there is little darkening , indicating the print is almost completely fixed.
However, IMO the pale yellow prints are of no use for display.Technically, the yellow color is probably produced in the same way as thiosulfate fixing as discussed by Dr Mike Ware:
https://books.google.co.uk/books?id=yA2N8Zl7JL4C&pg=PA78&lpg=PA78&dq=photolytic+silver&source=bl&ots=9HPDaehwET&sig=e_lrnsqPNT83GHU7M5zcm1qV4F8&hl=en&sa=X&ved=0ahUKEwiIy8jX65_UAhUFBMAKHbslAaQ4ChDoAQg6MAc#v=onepage&q=photolytic silver&f=false
I gave up on extended salt fixing and made a print by the traditional Fox Talbot stabilization method described in the link( pic), it is rust color rather than lavender.
https://jkschreiber.files.wordpress.com/2016/02/theartofphotogenicdrawing.pdf

 

[Alan Johnson]

http://resources.conservation-us.org/pmgtopics/1993-volume-five/05_10_Reinhold.pdf
Here is a description of Fox Talbot's early process (though any negative could be contact printed on such paper).
Since the stabilized print is darkened by light I tried to fix one instead, by immersion in near saturated salt solution at room temperature for 24 hrs.
The brown-purple pic is of the paper after exposure to sunlight for 3 min and washing ; the yellow pic shows the same after fixing in salt solution for 24 hrs.
A sample of the yellow print was placed in Rodinal !:50 for 20 min with some agitation, it did not darken, confirming that the yellow print was fixed.

So fixing of prints in salt solution is possible but who would want a yellow print.

 

[nmp]

http://resources.conservation-us.org/pmgtopics/1993-volume-five/05_10_Reinhold.pdf
Here is a description of Fox Talbot's early process (though any negative could be contact printed on such paper).
Since the stabilized print is darkened by light I tried to fix one instead, by immersion in near saturated salt solution at room temperature for 24 hrs.
The brown-purple pic is of the paper after exposure to sunlight for 3 min and washing ; the yellow pic shows the same after fixing in salt solution for 24 hrs.
A sample of the yellow print was placed in Rodinal !:50 for 20 min with some agitation, it did not darken, confirming that the yellow print was fixed.

So fixing of prints in salt solution is possible but who would want a yellow print. View attachment 180823 View attachment 180824

Hi, Alan:

Thanks for sharing your results. These simple but well thought-out experiments go a long way in clarifying, at least to my mind, what is happening when using the salt as stabilizer/fixer. My sense is that the color change is related to physical removal of the silver chloride resulting in smaller effective grain size responsible for light scattering - yellow being shorter than the red wavelength. Therefore, it would seem that unfortunately one can not remove the chloride (complete fixing) without the color change.

A question: How would the color of the exact same print post-salt compare with one that is fixed with hypo?

Good work!

Great link as well, by the way. Interesting that the Getty people learned their lesson for displaying an original Talbot print out in the open.

:Niranjan.

 

[NedL]

My sense is that the color change is related to physical removal of the silver chloride resulting in smaller effective grain size responsible for light scattering - yellow being shorter than the red wavelength. Therefore, it would seem that unfortunately one can not remove the chloride (complete fixing) without the color change.

I don't pretend to completely understand this. You are suggesting that somehow the silver chloride contributes to a larger grain size, for example, some AgCl could be involved in "holding together" the larger grains. If that is true, and it fits everything I've seen, then it does mean that it is physically impossible to fix the print without changing the color.

And in some ways the situation is even worse than you have suggested ( from the standpoint of trying to preserve the color ): if it was just that simple, it might be possible to heavily overprint and then recover the original color in the fix. But that doesn't work, and a heavily overprinted salt print will still turn brown in salt water and in hypo. So even if we overprint to the point of bronzing, when the AgCl is removed it divides even the biggest grains into small ones, just more of them! i.e. the AgCL is throughout the grain structure. Making bigger grains during printing cannot help.

I don't know if this is all true, but it sure fits the facts of experience very well. Honestly it's a little disappointing... I was still holding out some hope that the original color might be preserved somehow. Clive's approach of photographing the original with color film might be the closest we can get to "preserving" the look, short of storing an unfixed and unstabilized print in a dark drawer.

 

[cliveh]

I can recall that when I was making lots of photogenic drawings, I had a large supply of AgNo3 (about £1 a gram at the time) and was therefore able to make many experiments. My note keeping was non-existent, so I am not able to quote concentrations. However, I did conduct a series of tests where I varied both the silver nitrate concentration and salt concentration for the original sensitisation. Still stabilising with a saturated salt solution, I once produced an image with little colour, but was light fast in direct sunlight for many hours, and noticed no fading as though fixed. My conclusion is that with a certain combination of AGNo3 coupled with a certain concentration of salt will yield a very stable image. But this is just conjecture on my part and don’t experiment with those chemicals much these days.

 

[nmp]

I don't pretend to completely understand this. You are suggesting that somehow the silver chloride contributes to a larger grain size, for example, some AgCl could be involved in "holding together" the larger grains. If that is true, and it fits everything I've seen, then it does mean that it is physically impossible to fix the print without changing the color.

And in some ways the situation is even worse than you have suggested ( from the standpoint of trying to preserve the color ): if it was just that simple, it might be possible to heavily overprint and then recover the original color in the fix. But that doesn't work, and a heavily overprinted salt print will still turn brown in salt water and in hypo. So even if we overprint to the point of bronzing, when the AgCl is removed it divides even the biggest grains into small ones, just more of them! i.e. the AgCL is throughout the grain structure. Making bigger grains during printing cannot help.

I don't know if this is all true, but it sure fits the facts of experience very well. Honestly it's a little disappointing... I was still holding out some hope that the original color might be preserved somehow. Clive's approach of photographing the original with color film might be the closest we can get to "preserving" the look, short of storing an unfixed and unstabilized print in a dark drawer.

Ned:

That is my working theory at this point. I am sure it probably is simplistic and there are other interactions as well that affect which light wavelength gets out of the paper. Unfortunately there is no way of telling for sure unless one (not me) has access to a high powered electron microscope that would be required to test the theory.

As far as trying to manipulate the scattering particle size, I wonder if it might be more effective if you start with bigger AgCl particles in the first place - may be by eliminating gelatin to name one possible knob to turn. Or do an equivalent of emulsion "ripening" to grow the grains after sensitization. If you start in micron range before exposure, the resulting exposed print should be neutral. Then let the fixer "leach" it back to the particular sub-micron size that gives you that magic color. It sounds like a lot of work to figure out the exact conditions, though. Another route could be to do partial toning and additive toner like selenium or sulfide to build back the size to the desired color.

Happy experimenting!

:Niranjan.

 

[Gerald C Koch]

Gerald, as a chemist, do you not have any curiosity as to the history of your profession?

Is it not interesting to you understand what the processes were that were occurring when the alchemists of the 14th century were experimenting with their peculiar mixtures, and yet achieving something similar to what happens in today's laboratories?

You are after all, someone who frequently admonishes others to do their research before asking a question, and here we are undertaking collaborative research into the history of a photographic chemical process, and yet you admonish us for doing so!

Sometimes, it seems hard to "win" ... or, to put it another way, damned if you do, damned if you don't

One must distinguish between chemistry and alchemy.

Please it is simple to test for residual silver and find that soaking a film or print for any reasonable time in a salt solution does not remove enough silver from a the film or print to claim that it is fixed.

I know that some are always seeking a cheaper alternative but hypo is cheaper than film or paper.

 

[pdeeh]

One must distinguish between chemistry and alchemy.

Please it is simple to test for residual silver and find that soaking a film or print for any reasonable time in a salt solution does not remove enough silver from a the film or print to claim that it is fixed.

I know that some are always seeking a cheaper alternative but hypo is cheaper than film or paper.

You have spectacularly missed the point of my response.

Nothing in this thread is about trying to fix film and paper more cheaply than with hypo.

It is simply about trying to understand how talbot worked, and the chemistry thereof.

I would however really appreciate it if you were to contribute some commentary on the technical aspects of what is being discussed.

 

[Gerald C Koch]

Two comments. Fox-Talbot used a saturated salt solution. His early prints using this method quickly began to be fade. When John Herschel suggested using sodium thiosulfate Fox-Talbot started using it with far better results.

As to why a salt solution has any effect is based on the Common Ion Effect. The addition of extra chloride ions increases the solubility of silver chloride. However it increases the solubility but the majority remains insoluble. As for modern films which can contain silver iodide the CIE has no effect. We are forced to look at the Uncommon Ion Effect.

This topic often appears in posts where someone is looking for a cheap substitute for hype. Hence my comment.

My interest in discussing salt as a fixing agent is rapidly approaching zero.

 

[pdeeh]

OK Gerald I give up. I have the greatest respect for you and have learned much by reading your posts, but in this case you seem to be being deliberately obtuse. It really is rather disappointing.

 

[Gerald C Koch]

OK Gerald I give up. I have the greatest respect for you and have learned much by reading your posts, but in this case you seem to be being deliberately obtuse. It really is rather disappointing.

It is not my intent to be obtuse. Salt is not effective as a fixative for print salt prints. The CIE explains a decrease in the solubility of silver chloride. As far as silver iodide is concerned the Diverse Ion Effect commonly called the Uncommon Ion Effect comes into play. What more can I say?

(cut and paste error corrected)

 

[NedL]

I can recall that when I was making lots of photogenic drawings, I had a large supply of AgNo3 (about £1 a gram at the time) and was therefore able to make many experiments. My note keeping was non-existent, so I am not able to quote concentrations. However, I did conduct a series of tests where I varied both the silver nitrate concentration and salt concentration for the original sensitisation. Still stabilising with a saturated salt solution, I once produced an image with little colour, but was light fast in direct sunlight for many hours, and noticed no fading as though fixed. My conclusion is that with a certain combination of AGNo3 coupled with a certain concentration of salt will yield a very stable image. But this is just conjecture on my part and don’t experiment with those chemicals much these days.

You wrote about this once before. I've seen mention that there are different "kinds" or "states" of silver chloride, and I think it might be more than just whether there is excess silver nitrate available or not, but more about the relative concentrations of Ag and Cl. The very earliest calotypes ( like Talbot made ) were a kind called "pre-silvered", where the paper was first coated with a very weak solution of AgNO3, and then soaked in weak KI and washed. In this state, the paper has the "primrose" color of silver iodide, but it is not light sensitive. In fact, it was common practice to "sun" the papers in this state, which was thought to make the calotype more ready to be sensitive when the stronger layer of silver iodide was made. The instructions sometimes mention "converting" the light-insensitive type of AgI to light sensitive AgI.

What I'm getting at is that I wonder if something similar can happen with AgCl? Maybe there is an equilibrium state that is fairly stable and not very sensitive to light?

 

[Gerald C Koch]

Well the museum in Great Britain would certainly be happy if this were so. FT's original prints still fade when exposed to light and they have found no solution to the problem..

 

[NedL]

FT also used saturated KBr to "stabilize" prints, and he continued to do so occasionally even after learning about hypo from Hershel. Many of those prints still exist today ( which shows that they are not undergoing rapid spontaneous deterioration ), but as Jerry noted, they are still stored in the dark and only viewed in dim light. So they are not "fixed" in the way we usually mean to be light-safe.

This conversation is also relevant to fixing salt prints the normal way. The method proposed by APUG member Herzeleid in (there was a url link here which no longer exists) uses a strong 20% solution of ammonium chloride as a step prior to fixation. AgCl is somewhat soluble in ammonium chloride, and the solubility increases in stronger solutions. The ammonium chloride also presumably helps to convert even the tiniest minute amount of residual AgNO3 to silver chloride, so that it can be dissolved by hypo.

I've been trying this method for the past week or so, and there is a shift in color in the ammonium chloride bath that is consistent with what Niranjan wrote above. The shift in color is much more noticeable than if you put the salt print into NaCl solution, so I think the idea that some of the AgCl is dissolving is reasonable. And that there is (lesser) shift in color in plain NaCl solution is explained by what Jerry wrote. All of this probably matters in normal hypo-fixed salt prints if you are trying to keep the highlights bright, eliminate chemical fogging, and have the print be light-safe at the end.

So even though fixing in salt is not very practical, this discussion around it is very illuminating. I know I still have a lot of questions about what actually is happening in the paper... are the Ag and Cl ionic? How much does humidity matter, and whether other ions present are hygroscopic or hygrophobic, etc. etc.

Well, anyway, I actually have a salt print exposing right this second, and I need to go out now and have a look at it. I will however, un-authentically, fix it in hypo

 

[nmp]

O'Reilly explains the issue of color change during fixing thusly....

COLOR CHANGES DURING FIXATION
During fixation the prints undergo a dramatic change in color, in which the original brilliant purple or brown color is transformed into a much yellower and duller brown hue, accompanied at the same time by a loss of density. The reasons for this color and density change--a characteristic phenomenon in all silver printing-out papers--have to do with the physical structure of the metallic silver which forms the image. In an exposed but unfixed print the silver image particles exist in a highly dispersed state, forming a kind of "solid solution" of metallic silver in silver chloride. The color and density of this system is determined by the size and amount of metallic particles as well as the combined refractive indices of silver chloride and whatever binder materials have been used on the paper.

Upon fixation the silver chloride is removed and the metallic silver particles undergo a "packing" process and accumulate into aggregates of particles. At the same time the refractive index of the system is lowered by the removal of the silver chloride. Together these physical and chemical changes cause a loss of particle covering power i.e., print density and shift the color of the print toward yellow. In fact, any physical change in the image layer causes a shift of print color. A good example of this is the reddening of prints that occurs when they are placed in the initial wash water; swelling of the image layer is the actual cause of the color shift. When prints dry they undergo another change, becoming more neutral in color and gaining slightly in density as the image layer contracts.

From:
http://albumen.conservation-us.org/library/monographs/reilly/chap9.html

 

[NedL]

Niranjan,

Somehow I think Reilly's description is oversimplified, or there are other important factors, even if it does describe the general situation. Your description fits certain facts better. I think the fixation step must also modify the silver particles which are left to be "packed" in some way analogous to what you wrote, and whether the change in particles themselves or change in their relative physical position is most important to the color change might depend on the details.

For example, the red shift he mentions is much more apparent if the initial wash water has salt in it. You can even force a shift to red after a couple distilled water washes by placing the print in NaCl salted water. It seems there is more to it than physical swelling. And recently I've been using Herzeleid's strong ammonium chloride bath, and the shift to yellow-brown is nearly complete... after that, it hardly changes at all in the hypo. But silver chloride is only mildly soluble in ammonium chloride, and is completely soluble in hypo, so this "repacking" scenario can't explain everything: I think the silver particles themselves must be getting changed pretty dramatically, as well as being "repacked". If the "repacking" was the dominant effect, the stronger color shift should be in the hypo, and that's not what happens.

Also, what about highlights? If you print until there are only faint highlight details, the details can "bleach away" to paper white in the fixation step. This happens even after toning. In fact it was common practice in the early days to use extended hypo bath ( even to many hours ) to brighten up highlights. It seems to me the particles themselves must be getting reduced in size (to the point of becoming invisible!). If it was just a matter of packing, wouldn't the highlights remain, but just shift color?

Also, I have a bit of speculation. I think that toner can still act on aggregate silver particles held together by some AgCl ( using your analogy ), but not so much once the "aggregate" has been disrupted. I thought of this after reading your post. I made two prints in the past week, and the one that had shifted strongly to yellow-brown in ammonium chloride would not tone very well, while a second similar print was toned after a weak NaCl + NH4Cl bath and it toned very rapidly. This needs further testing because the 2nd print also had a little more exposure, but it fits some other facts about toning as well.

Your way of describing it fits these details better than Reilly's. Not that Reilly's "rearrangement" isn't happening, but it's not enough to explain what happens when you actually make a print and are trying to make a better one.

It's sort of amazing how complicated such a "simple" process is!

 

[Alan Johnson]

It's not known if the theory of particle size change applies to other fixers besides thiosufate and chloride.
For example, thiourea is reported to convert silver to the stable sulfide form and thiocyanate to work by converting oxidized silver to a stable insoluble salt.
http://unblinkingeye.com/Articles/Archival/archival.html
They are both to be found in PE's "Superfix" for films and do not appear to have been tried for the early papers discussed here.
https://www.photo.net/discuss/threads/super-fix.141359/

 

[NedL]

Thanks Alan I'll go read those later ( I have to sensitize a salt print right now ). But that's fascinating and it actually adds fuel to this line of reasoning.
Sodium thiocyanate definitely does shift the color of a salt print... I've tried it. But it also dissolves AgCl, so that color change fits Niranjan's narrative very well: it would still break up "aggregate clumps" of Ag held together by AgCl.

And you're absolutely right, it might not be very similar to the Ag particles that "grow" in a developed-out emulsion. Gotta' run to go have some fun!

 

[pdeeh]

During fixation the prints undergo a dramatic change in color, in which the original brilliant purple or brown color is transformed into a much yellower and duller brown hue, accompanied at the same time by a loss of density. The reasons for this color and density change--a characteristic phenomenon in all silver printing-out papers--have to do with the physical structure of the metallic silver which forms the image.

{my emphasis}

The discussion really has reached beyond the limits of my understanding of most of the chemistry involved, but I would like to make one observation on the matter of colour & density change: In Namias' Papier sepia process (an Iron-Silver process, with which Ned is familiar, and upon which I won't enlarge (as there is a running thread started by Ned on the subject)), an exposed print is first washed (significant increase in contrast and density) and then fixed in hypo. As soon as the print hits the hypo, contrast and density increase again.

Rodolfo Namias himself speculated "I am inclined to attribute this to a slight sulphurization, facilitated probably by by traces of iron present in the image."

So this would perhaps be an effect limited to Iron-Silver processes, rather than the Silver halide only processes.

As I say, just an observation to refine O'Reilly's statement "a characteristic phenomenon in all silver printing-out paper"

 

[cliveh]

{my emphasis}As soon as the print hits the hypo, contrast and density increase again.

Not in my experience.

 

[nmp]

It's sort of amazing how complicated such a "simple" process is!

A lot to digest this afternoon. But the above is probably the truest statement of all.