What exactly is the requirements of a Kallitype developer?

I've been trying to find info about the chemistry that makes Kallitype work, and I think I understand it to an extent, but I do not understand how the developer ties into it. There's a few often used developing agents include:

* acetate
* citrate
* oxalate (references to it, but very little documentation)
* tartrate (rochelle salts)

And all of these salts used in extremely high volume amounts, nearly at the saturation point typically, and often kept at least mildly acidic.

I'm trying to understand why these salts are used and why not acidified distilled water (similar to cyanotypes)? I've personally tried potassium oxalate, sodium citrate, and (just recently) triethanolamine acetate (acetic acid + triethanolamine). All seem to work similarly but with distinct tone differences. Citrate is typically very warm and orange. Oxalate can be extremely cold toned, even blue on some papers but can be orange on some papers too, and triethanolamine acetate I haven't tested enough, but it seems to be a warm deep brown with cold highlights in initial tests. All developers kept acidic using the acid version of the salt (ie, citric acid, oxalic acid, acetic acid respectively). I know distilled water or diluted developers (even when acidic) also typically lead to staining in highlights.

I don't understand how each different developer produces different tonalities, or what actually makes this work in this case. I understand chelating and clearing is important, but that's the clearing bath and not the developer. My understanding is actually more that a chelating agent would prevent development, but obviously that isn't the case. Does anyone have anything to read on this subject? I see a ton of "how to kallitype" but very little "how kallitypes work" type information. There's one previous thread here thats old but also didn't go into what makes a developer work for the process, just suggesting potential developers

Let me preface my response by stating that I am a biochemist by training and thus have some knowledge of inorganic chemistry, but I am certainly not an expert in this area.

As for the pH, one would want to keep the pH low to prevent the formation of iron hydroxide and iron oxide which are not very soluble in water and would thus make it difficult to clear the iron from the paper. This leads to the yellow/orange stains that form over time if the paper contains residual iron.

As for why use a chealator, I think the answer is efficiency. Complexing the iron with a chealator increases its solubility in water and therefore makes it easier to clear.

I have no clue as to the chemical reactions involved in the development of kallitypes, but I can speculate that the differences in tonality are due do to differences in how well the various compounds bind to iron.

These compounds, while similar at one level, all have very different structures and as we chemists are wont to say "structure equals function". Acetate is a monodentate ligand... it has one site (carboxylic acid group) for binding iron. Citrate is tridendate and oxalate and tartrate are both bidentate. Triethanol amine is a tridentate ligand, but the binding sites are alcohol groups not acid groups.

The binding of iron by these compounds is a very complex subject and I won't attempt to describe it here. Suffice to say that the different ligands will bind the two forms of iron (ferrous and ferric) differently and those differences will be different for each of the ligands.

These differences in binding will be reflected in differences in the rate of what ever reactions occur during development as well as the nature of the products made by those reactions and thus the tone of the colored products that comprise the image.

Hopefully, this response is useful to you. My argument is a bit of the hand waving type, but it us the best I can do!

earlz said:

I've been trying to find info about the chemistry that makes Kallitype work, and I think I understand it to an extent, but I do not understand how the developer ties into it. There's a few often used developing agents include:

* acetate
* citrate
* oxalate (references to it, but very little documentation)
* tartrate (rochelle salts)

And all of these salts used in extremely high volume amounts, nearly at the saturation point typically, and often kept at least mildly acidic.

I'm trying to understand why these salts are used and why not acidified distilled water (similar to cyanotypes)? I've personally tried potassium oxalate, sodium citrate, and (just recently) triethanolamine acetate (acetic acid + triethanolamine). All seem to work similarly but with distinct tone differences. Citrate is typically very warm and orange. Oxalate can be extremely cold toned, even blue on some papers but can be orange on some papers too, and triethanolamine acetate I haven't tested enough, but it seems to be a warm deep brown with cold highlights in initial tests. All developers kept acidic using the acid version of the salt (ie, citric acid, oxalic acid, acetic acid respectively). I know distilled water or diluted developers (even when acidic) also typically lead to staining in highlights.

I don't understand how each different developer produces different tonalities, or what actually makes this work in this case. I understand chelating and clearing is important, but that's the clearing bath and not the developer. My understanding is actually more that a chelating agent would prevent development, but obviously that isn't the case. Does anyone have anything to read on this subject? I see a ton of "how to kallitype" but very little "how kallitypes work" type information. There's one previous thread here thats old but also didn't go into what makes a developer work for the process, just suggesting potential developers

Click to expand...

I find this early 20th century book very useful in learning the chemistry behind photographic processes and it's free to download - check out the chapter on Iron-based Processes:

https://www.google.com/books/editio...4lALAQAAIAAJ?hl=en&gbpv=1&printsec=frontcover

Somethings might be outdated, but generally it is still relevant.

Then there is Mike Ware's Platinomicon where many of the concepts behind platinotype are applicable to kallitype as well - the difference being the metal salt that is reduced.

There was also a thread here that might be of use:

https://www.photrio.com/forum/threads/the-chemistry-of-kallitypes.144668/#post-1897600

Basically, a critical difference between processes like cyanotypes, VDB, POP Pt/Pd, etc. that use ammonium based sensitizer (FAC or FAO) and classical Pt/Pd, kallitype etc that use ferric oxalate is that in the former the product of photo-reduced sensitizer is soluble in water while in the latter group it is not. Once the ferric has been converted to ferrous, it then being a strong reducing agent reacts with the metal salt to precipitate the metal. Reaction obviously requires a liquid medium where mass transfer of various components can occur easily.

For cyanotypes and others in the first group, some of that already starts occurring while being exposed since there is moisture around in the paper - so one gets a POP print. Rest can be achieved by simply dunking in plain water or acidified water - the latter primarily to counter hydrolysis of iron salts so as not to precipitate insoluble iron hydoxide that would be difficult to remove. Same goes for FAO based Pt/Pd.

For FO based system the product is ferrous oxalate that is only sparingly soluble in water. So water won't work as it did before. In order to facilitate the reaction between ferrous oxalate and metal salt then, an additional "solvent" molecule is required which will complex with ferrous oxalate and carry it up to the next available metal salt and do its thing. Hence the need for citrates, acetates, oxalates etc. I guess the color difference in various developers are related to kinetics of various steps (tied to the structural differences as alluded by Frank) involved that results in variation in the size of the particles of precipitated silver - smaller they are warmer they get. It is probably complicated further by the paper as well as temperature of the developer.

:Niranjan.

Hmm quite informative. So basically the key factor in determining "will this be a kallitype developer" is if adding it to water (or using an entirely different solvent) will cause ferrous oxalate to become more soluble, while also of course not causing hydrolysis. I don't have any dry FO to test this out on, but I assume one could test for this by simply adding a few crystals of ferrous oxalate (made by leaving some ferric oxalate out in sunlight), and drop it into the mixed chemical. If it quickly dissolves, its a developer, if not then it is not.

In this case, my own triethanolamine acetate experience should be very suitable, as both acetate and triethanolamine will complex with ferric and ferrous compounds. It'd be interesting if I could find an acid that is NOT a developer and see the action of TEA on its own. Unsure if sulfuric acid/sulfate would be a developer in this case, I'd think so (ferrous sulfate exists afterall). I guess this dives even deeper into the chemistry, but I know ferrous sulfate can be used as a developer for traditional silver halide materials (very slow, and very prone to hydrolisis). I wonder why ferric oxalate is required for the process, and why ferric sulfate couldn't be used. Both are sensitive to UV, giving the reduced iron form. I suppose I could try it out by some synthesis since I have peroxide (or permanganate) and ferrous sulfate laying around. In that case, since ferrous sulfate is much more soluble, in theory it wouldn't need a "developer" and rather plain water would work

earlz said:

I guess this dives even deeper into the chemistry, but I know ferrous sulfate can be used as a developer for traditional silver halide materials (very slow, and very prone to hydrolisis).

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These are two different concepts of developing. In the traditional DOP silver gelatin films and paper, the developer chemically amplifies the kernel of silver that is created with exposure by reducing the silver halide around it by use of a suitable reducing agent. Ferrous sulfate is one such reducing agent, hence it can be used a developer there. In the alternative process universe, the word "developer" is unfortunately a misnomer or it connotes a different meaning, hence the quotation marks. It does not add to or multiply the photo-chemistry that happened in exposure. You can't make a kallitype all dark if developed long enough, like you can do in silver gelatin. You do get the latent image on exposure that seems to come to life when the developer is poured over, which is a hallmark of the traditional developed-out silver gelatin.

earlz said:

I wonder why ferric oxalate is required for the process, and why ferric sulfate couldn't be used. Both are sensitive to UV, giving the reduced iron form. I suppose I could try it out by some synthesis since I have peroxide (or permanganate) and ferrous sulfate laying around. In that case, since ferrous sulfate is much more soluble, in theory it wouldn't need a "developer" and rather plain water would work

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You can already do water-developed kallitype - but then it becomes VDB... The latter uses FAC that requires only water to develop like cyanotypes. End product in both cases is same - image formed by silver metal.

:Niranjan.

nmp said:

These are two different concepts of developing. In the traditional DOP silver gelatin films and paper, the developer chemically amplifies the kernel of silver that is created with exposure by reducing the silver halide around it by use of a suitable reducing agent. Ferrous sulfate is one such reducing agent, hence it can be used a developer there. In the alternative process universe, the word "developer" is unfortunately a misnomer or it connotes a different meaning, hence the quotation marks. It does not add to or multiple the photo-chemistry that happened in exposure. You can't make a kallitype all dark if developed long enough, like you can do in silver gelatin. You do get the latent image on exposure that seems to come to life when the developer is poured over, which is a hallmark of the traditional developed-out silver gelatin.



You can already do water-developed kallitype - but then it becomes VDB... The latter uses FAC that requires only water to develop like cyanotypes. End product in both cases is same - image formed by silver metal.

:Niranjan.

Click to expand...

Yes, but in using ferric sulfate, the idea would be that no complexing agent is needed and the result would be a mostly DOP process where water is the developer, basically the nearby ferrous sulfate just needs to reduce the silver nitrate. VDB I think works a bit differently in that it is much closer to a printing out process (the aim is a lot more density during exposure rather than "a whisper"). I'm unsure of the chemistry here, but I imagine the mechanics of VDB is more that the ferrous citrate salt readily with the silver nitrate while "dry but nearby", while for kallitypes it does not react like this and must have something to solubilize the ferrous salt first. Is this difference only dependent on water solubility? (ie, would VDB actually not work at bone dry humidity?) If so then ferric sulfate would work, but make something similar to a VDB. I've seen one reference use iron-only printing by using ferric sulfate and oxalic acid, which was "very fast" (cyanotype exposure being typically 10m, this was 45s) and produced a deep brown image, and oddly was "developed" by a ferricyanide bath. I can only assume this somehow made a complex of ferric sulfate and oxalic acid, which reduced to ferrous during exposure, and then the ferricyanide was reduced to ferrocyanide and ferric... something? was left behind. Either way I have a dirty batch of ferric sulfate (fun fact ferrous sulfate + peroxide produces a lot of heat) now that I'll make a test print from just to see if there is actual potential of a kallitype-like process from this.

Another interesting thing I don't see talked about much in kallitypes is the ratio of FO to silver. I accidentally used 20% silver instead of the typical 10% and the results were extremely warm tone, like salt prints. Then I went the opposite way accidentally and had more FO than silver and the results were a lot colder in tone, but also much easier to solarize. (required very precise exposure to get deep cold blacks without solarizing them into a warm brown)

I don't know how effective a photo-sensitizer ferric sulfate is by itself. If it was good, we would have been using it - I suspect. It has been used in conjunction with oxalic acid, but then it is just formation of ferric oxalate in-situ. Then the same issue of having to use the so-called developers to make the image applies.

VDB bone dry if you can prepare such a coating will work, only the latent image or the POP image will presumably be fainter. Moisture in the paper in a sense makes the paper with an embedded developer - again we are using the word developer loosely. But then when water hits the print, the silver nitrate reduction reaction can occur and the image would form in proportion to the ferrous ions produced during exposure. Now if the photo-efficiency is lower without moisture (that I am not aware of one way or other,) that would be a different matter.

Be careful of that ferrous sulfate - hydrogen peroxide combination !

:Niranjan.

Abney wrote a paper on the actinic sensitivity of various iron salts.... my memory is that ferric chloride + oxalic acid was the most sensitive, followed by ferric oxalate, and then ammonium or potassium ferric oxalate, then AF tartrate followed by AF citrate. You could probably find the paper with some google-fu. I don't remember ferric sulfate being mentioned, but it's been quite a while since I read it.

nmp said:

I find this early 20th century book very useful in learning the chemistry behind photographic processes and it's free to download - check out the chapter on Iron-based Processes:

https://www.google.com/books/editio...4lALAQAAIAAJ?hl=en&gbpv=1&printsec=frontcover

Somethings might be outdated, but generally it is still relevant.

Then there is Mike Ware's Platinomicon where many of the concepts behind platinotype are applicable to kallitype as well - the difference being the metal salt that is reduced.

There was also a thread here that might be of use:

https://www.photrio.com/forum/threads/the-chemistry-of-kallitypes.144668/#post-1897600

Basically, a critical difference between processes like cyanotypes, VDB, POP Pt/Pd, etc. that use ammonium based sensitizer (FAC or FAO) and classical Pt/Pd, kallitype etc that use ferric oxalate is that in the former the product of photo-reduced sensitizer is soluble in water while in the latter group it is not. Once the ferric has been converted to ferrous, it then being a strong reducing agent reacts with the metal salt to precipitate the metal. Reaction obviously requires a liquid medium where mass transfer of various components can occur easily.

For cyanotypes and others in the first group, some of that already starts occurring while being exposed since there is moisture around in the paper - so one gets a POP print. Rest can be achieved by simply dunking in plain water or acidified water - the latter primarily to counter hydrolysis of iron salts so as not to precipitate insoluble iron hydoxide that would be difficult to remove. Same goes for FAO based Pt/Pd.

For FO based system the product is ferrous oxalate that is only sparingly soluble in water. So water won't work as it did before. In order to facilitate the reaction between ferrous oxalate and metal salt then, an additional "solvent" molecule is required which will complex with ferrous oxalate and carry it up to the next available metal salt and do its thing. Hence the need for citrates, acetates, oxalates etc. I guess the color difference in various developers are related to kinetics of various steps (tied to the structural differences as alluded by Frank) involved that results in variation in the size of the particles of precipitated silver - smaller they are warmer they get. It is probably complicated further by the paper as well as temperature of the developer.

:Niranjan.

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Niranjan,

Thanks for the references, Despite begin a chemist, my knowledge of the chemistry underlying most photographic processes is limited. I am, at this point in my life, more interested in the art than I am in the science I guess.

NedL said:

Abney wrote a paper on the actinic sensitivity of various iron salts.... my memory is that ferric chloride + oxalic acid was the most sensitive, followed by ferric oxalate, and then ammonium or potassium ferric oxalate, then AF tartrate followed by AF citrate. You could probably find the paper with some google-fu. I don't remember ferric sulfate being mentioned, but it's been quite a while since I read it.

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Ned,

I am not familiar with the paper you mention, but here is another article regarding the photo-sensitivity of various iron carboxylate complexes: https://www.sciencedirect.com/science/article/abs/pii/002016939404077X

As I understand it purely inorganic iron salts are fairly insensitive to light. Adding a carboxylic acid such as oxalate vastly increases the speed of the photochemical reaction. As mentioned in the abstract to the article I cite above, the light-induced reduction in iron carboxylate complexes is accompanied by the decarboxylation (lose of CO2) from the acid.

In my own (limited) experience investigating the (as yet incomplete) ferric gum process I certainly saw that ferric chloride was photosensitive by that adding citrate (if my memory serves) vastly increased the speed of the process. I would image the same holds true for the sulfate.

I haven't been able to find a paper by Abney, but I did come across an article from 1874 titled "Note on Salts of Iron Sensitive to the Action of Light" by William H Watson (pdf version on my web server).

I tested my home made ferric oxalate and it does work, but like a much more mild version of oxalate. I believe ferric sulfate is not soluble enough in water to get a good concentration for coating (ferrous sulfate is easily soluble while ferric is only sparingly). It would be interesting to consider a coating of ferrous sulfate, then go over it with a coating of peroxide, and then finally over it once more with silver nitrate... but multiple coatings like that tend to only add problems for minimal benefit. Regardless, the experiment was informative but ultimately a wash. I found that the best reaction I got was when the solution was rather chunky. I stirred the solution around (a lot of ferric sulfate at the bottom that didn't dissolve), and then used a syringe to pick up both crystals and solution and put 15 drops of it, and 8 drops of silver nitrate 20%. The result was a considerably more sensitive emulsion which was easily fogged by standard room lights, but also was easily coated unevenly due to the crystals left in the solution. The result using my TEA-acetate "developer" was perfect clearing, and a deep brown density (with grey highlights), but the coating problems resulted in brush lines on the print that were darker than the rest, and overall dmax does not compare well to proper kallitypes. Overall contrast was much lower, and it seemed to want to be more of a van dyke style process that prints out more than oxalate, but not as much as proper van dyke. Also fun fact if attempting it at home like me. Citric acid will make the ferric sulfate much more soluble for easier clean up, and a bit of hydrochloride (muriatic) acid is absolutely incredible for cleaning up any remaining red stains on glass ware, just be careful because it's a pretty crazy acid for being able to buy it at your local hardware store.

A fun experiment to do, but ultimately not useful for what I want to accomplish, back to regular ol' ferric oxalate. I think I'm now starting to understand why oxalate developers require a "developer" though. Really the developer is more of a solubility agent. Without it, the silver nitrate would wash away faster than the ferric oxalate could interact with it. I don't understand why citric acid or other acids aren't used instead of their salts though, and what effect does pH have on the "developer"? In theory I'd guess too low of a pH will restrain the short lived "development" (since ferrous salts are less reductive at low pH), but it's still pretty difficult to make sense of. I also know many of these acids will complex with silver nitrate as well at least for acetic acid, citric acid, and oxalic acid. Unsure about rochelle salts/borax. TEA also can form a complex with iron and silver compounds (iron more easily than silver), but there's been basically no one crazy like me to try to use it for kallitypes so I'm still in uncharted territory there.

Before I say ferric sulfate is a total wash, I accidentally created a direct positive iron image from a test strip I had left over. Developer contained TEA, hydroxide (pH ~12) and ascorbic acid. Attached image shows the result after bleaching (with ferricyanide) and fixing the top portion of the print. The remaining image is poor (high dmin, poor dmax), but appears to be a pure iron based image. I tried replicating the result without silver, but instead only got a mild grey dmin and no apparent light sensitivity (no image). This could be because I was impatient about waiting for the ferrous sulfate to finish reacting, or the silver actually serves a key purpose. I have no idea how this could really happen though upon analysis. In theory it should be possible to lay down an iron based negative image by adding a strong reducer like ascorbic acid to the developer, but I'm completely unsure why unexposed ferric sulfate would reduce to metallic iron first, creating a positive image.

Also FYI, TEA is also confirmed to be a reasonable traditional kallitype developer AND clearing agent. Even at highly alkali pH, TEA will complex with any ferric and ferrous hydroxide produced, leaving perfect clear whites after development, and then following with a regular tap water rinse. Using a citric acid stop bath afterwards would actually be a bad idea in this case because the Fe-TEA complex breaks at low pH. The image produced is fairly warm tone. Not as warm as citrate, but much warmer than the TEA-Acetate I was using. My coating was kind of bad on the test print I used, but it seems to produce a deep warm brown, and grey-orange highlights

earlz said:

I tested my home made ferric oxalate and it does work, but like a much more mild version of oxalate.

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-What do you mean by "home made ferric oxalate?" Did you use oxalic acid? Or just ferric sulfate?

earlz said:

A fun experiment to do, but ultimately not useful for what I want to accomplish, back to regular ol' ferric oxalate. I think I'm now starting to understand why oxalate developers require a "developer" though. Really the developer is more of a solubility agent. Without it, the silver nitrate would wash away faster than the ferric oxalate could interact with it. I don't understand why citric acid or other acids aren't used instead of their salts though, and what effect does pH have on the "developer"? In theory I'd guess too low of a pH will restrain the short lived "development" (since ferrous salts are less reductive at low pH), but it's still pretty difficult to make sense of. I also know many of these acids will complex with silver nitrate as well at least for acetic acid, citric acid, and oxalic acid. Unsure about rochelle salts/borax. TEA also can form a complex with iron and silver compounds (iron more easily than silver), but there's been basically no one crazy like me to try to use it for kallitypes so I'm still in uncharted territory there.

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Most of the acids you mention will make insoluble salts with silver, so they can't be used to clear unreacted silver - that's why you fix in the end with thiosulfate. They also won't make effective "solubility agents' as you describe (which is a good way to put it, by the way) for ferrous oxalate, so not good as developers. If they did, there would have been no need to use any of the exotic chemicals such as sodium citrate or potassium oxalate. But you can see for yourself by trying to develop a regular kallitype with citric acid or oxalic acid.

TEA, by the way, might have some health concerns - amines are not very friendly in general so do check out the MSDS on that one.

:Niranjan.

earlz said:

Before I say ferric sulfate is a total wash, I accidentally created a direct positive iron image from a test strip I had left over. Developer contained TEA, hydroxide (pH ~12) and ascorbic acid. Attached image shows the result after bleaching (with ferricyanide) and fixing the top portion of the print. The remaining image is poor (high dmin, poor dmax), but appears to be a pure iron based image. I tried replicating the result without silver, but instead only got a mild grey dmin and no apparent light sensitivity (no image). This could be because I was impatient about waiting for the ferrous sulfate to finish reacting, or the silver actually serves a key purpose. I have no idea how this could really happen though upon analysis. In theory it should be possible to lay down an iron based negative image by adding a strong reducer like ascorbic acid to the developer, but I'm completely unsure why unexposed ferric sulfate would reduce to metallic iron first, creating a positive image.

Also FYI, TEA is also confirmed to be a reasonable traditional kallitype developer AND clearing agent. Even at highly alkali pH, TEA will complex with any ferric and ferrous hydroxide produced, leaving perfect clear whites after development, and then following with a regular tap water rinse. Using a citric acid stop bath afterwards would actually be a bad idea in this case because the Fe-TEA complex breaks at low pH. The image produced is fairly warm tone. Not as warm as citrate, but much warmer than the TEA-Acetate I was using. My coating was kind of bad on the test print I used, but it seems to produce a deep warm brown, and grey-orange highlights

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I doubt you have a pure iron image - more likely a Fe(OH)3 image.

Try making a print with no ferric of any kind, just silver nitrate and you will see you an get a pretty good image (as long as you are using buffered paper.)

:Niranjan.

fgorga said:

Niranjan,

Thanks for the references, Despite begin a chemist, my knowledge of the chemistry underlying most photographic processes is limited. I am, at this point in my life, more interested in the art than I am in the science I guess.

Click to expand...

You are welcome. I am sure I got the link from someone else on the forum. It's a challenge to switch off the logical/scientific brain to focus on the art. But then people like us who are trained first in the sciences, part of the allure for alternative processes is the ability to tinker with their technical aspects. Have to focus on the end point though, which is to create art, but it very easy to get bogged down on the minutia of the details and miss the forest for the tree.

Looks like you decided to get in on the action too judging from the research you are sharing....

nmp said:

-What do you mean by "home made ferric oxalate?" Did you use oxalic acid? Or just ferric sulfate?



Most of the acids you mention will make insoluble salts with silver, so they can't be used to clear unreacted silver - that's why you fix in the end with thiosulfate. They also won't make effective "solubility agents' as you describe (which is a good way to put it, by the way) for ferrous oxalate, so not good as developers. If they did, there would have been no need to use any of the exotic chemicals such as sodium citrate or potassium oxalate. But you can see for yourself by trying to develop a regular kallitype with citric acid or oxalic acid.

TEA, by the way, might have some health concerns - amines are not very friendly in general so do check out the MSDS on that one.

:Niranjan.

Click to expand...

I meant ferric sulfate, though I also did a single test with plain (not home made) ferric oxalate, which produced no reaction without silver

Yes, I didn't intend for the TEA to be a fixer, but rather to eliminate the clearing bath step (typically citric acid or EDTA)... however, in theory it would actually require less fixing than other developers. TEA will not react with silver nitrate to form anything insoluble, so in theory IFF the only form of silver on the paper is silver nitrate and silver metal, then fixing would be "optional". However, I think it's impossible to prevent silver nitrate from reacting with stuff in the paper, so fixing is likely still needed for archival processing. I did notice that unlike a regular developer though, the tonality change in the fixer is extremely minimal if not non-existent, also indicating that the remaining silver nitrate stays behind in the development solution. It's conceivable I think to consider that this could be a "almost but not quite" archival monobath for kallitype, excluding the toning of course.

TEA is not bad, but DEA and MEA are quite a bit more concerning (and much more smelly). I'm using 99% TEA with minimal impurity (other than some extra water). TEA is often used in soap making, shampoos, and ointments, though of course it is neutralized and not used as-is. DEA is also used, and DEA neutralized by coconut oil is a common foaming agent... though also listed as a possible carcinogen heh. Either way, wear gloves etc but this seems safer than oxalic acid salts honestly.

Regarding iron image, it is definitely possible I'm generating some ferric hydroxide, but I can confirm there are no ferrous salts left behind since they'd turn to prussian blue in ferricyanide. I'm unsure how to test for ferric hydroxide in a way that won't affect metallic iron though. I will run a test later to confirm if ferric hydroxide is solubilized by TEA as research seems to say though, in which case even if some were generated it wouldn't actually matter. Regardless, as long as either pure ferric hydroxide or pure metallic iron is being generated and the silver is bleached away, then it would be fairly "archival" (well, as archival as iron can be)

And yes, I've made salt prints and some test prints using just silver nitrate. The big difference between that and kallitypes is the sensitivity and speed. Salt prints take ~1 hour to expose in my setup and kallitypes take 5 minutes. Kallitypes also have more contrast due to the lack of compensated shadows (ie as density comes up in POP process, it slows down rate of exposure)

For your enjoyment, I tested a few Kallitype developers. All exposed very similarly (maybe a few seconds of difference), untoned, fixed in plain thiosulfate for 45s. I tested 3 developers:

* Potassium Citrate (and pinch of citric acid) developer, citric acid clearing bath
* TEA+Acetic acid at pH 6 (TEA acetate with a small surplus of acetic acid), citric acid clearing bath
* TEA alone, with very dilute TEA clearing bath (note: alkali process, ~pH 12 for developer, 9 for clearing bath)

The difference in results was actually pretty surprising to me. Given how the the "developer" is really a misnomer, it doesn't make much sense that they'd give such a big difference. I scanned each sheet altogether to ensure no scanning algorithm differences, and slightly edited to match the real appearance of the print (my scanner always makes things a bit blue). There is also some contrast curve differences, though the overall range between all of them is very close. On the TEA only developer, it had the deepest blacks and also the least appearance of solarization. On Citrate and TEA-Acetate you can see on the step wedge it gets dark, but then lightens up at deeper steps due to solarization. Another thing to note is that despite using the same clearing bath and procedure between citrate and TEA-acetate, the TEA-acetate one has a very yellow base. The citrate base is an extremely mild grey (looked somewhat blue when wet) while the TEA-only base looks the closest to white.

Note: on my step wedge, bottom row has a small piece of black tape to judge unexposed areas, and there is a circle notch in the 1 step to show maximum exposure. Paper was coated using 15 drops of ferric oxalate 20% and 7 drops of silver nitrate 20%. I found this ratio to be surprisingly critical to contrast, speed, and overall tonality. More silver is sometimes recommended than oxalate, but I found that this produces lower contrast, lower dmax, lower speed, and much warmer tones. The ratio I'm using is the one I like best that I've tried.

I think the biggest concern with using TEA is just that it is not perfectly reusable and not super cheap (though buying 1 gallon can be done for $20 or $30). It will become orange with use but with no precipitate, I believe due to silver nitrate and ferric hydroxide complexes made with the TEA, but it's fairly easy to overload the TEA. since ferric hydroxide-TEA complex has a fairly low solubility. Also this complex will break in acids or strong bases. So, you have to have enough TEA in solution to ensure it's pretty well saturated, but not so much that the pH would rise above 12.5 or so. I think 30% TEA is probably the right number to aim for. Also because the complex will break in acids, the clearing bath can not be an acid. I instead dropped a few ml of TEA into some distilled water and used that for clearing, with the purpose there really be to dilute that complex so that little if any will break when washing with tap water. I'm unsure a clearing bath is strictly necessary though. The next question is how does developer tonality affect actual toning in a truly archival process. I don't have any good toners other than gold and selenium (platinum is expensive!) but I doubt I'll do a similar step wedge comparison with those. I also have some rochelle salts and sodium acetate coming in this weekend that I might use to make a comparison between them. However, I think it's safe to say TEA is a good (if not the best due to dmax) developer and clearing agent for Kallitypes that is capable of producing archival results, of course with toning still being a likely requirement

Image of the step wedges: (photrio upload size limits are annoying) https://i.imgur.com/sZ6vcp8.jpg

Good work there.....thanks for sharing. TEA acetate one is intriguing - highlights are stained yellowish but the actual tone of the steps are quite neutral compared to the others.

How did you come about using TEA, by the way - I don't see it mentioned much in the references.

:Niranjan.

nmp said:

Good work there.....thanks for sharing. TEA acetate one is intriguing - highlights are stained yellowish but the actual tone of the steps are quite neutral compared to the others.

How did you come about using TEA, by the way - I don't see it mentioned much in the references.

:Niranjan.

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I have way too much TEA (3 gallons or so) and been looking to use it somewhere other than in my GVK1 developer formula. I know from a lot of other research that it's really good at complexing with iron, and with a bit more research figured it might be the solution to completely avoid the ferric hydroxide problem using it despite working at a highly alkaline pH.

The TEA-acetate stuff seems to resemble regular sodium acetate, but I didn't have any on hand so I made my own with some glacial acetic acid and TEA instead of sodium hydroxide. The solution might actually not be concentrated enough and this is what is causing the yellowing. I only have about 1L of acetic acid so didn't want to use it all up on this

Interesting work. Thanks for sharing.

A couple of chemical comments...

I would expect that the neutral triethanolamine, which exists at high pH, should complex iron much better than the positively charged triethanolammonium ion you make by adding acid to the TEA. If you are interested in the details of this chemistry, I can write out the equation... just let me know.

I would also be worried about the yellowing you observe in the last case. It is likely to get worse over time.

Amines, in general, will, even in pure form, go yellow or brown over time upon exposure to air. They oxidize to make a variety of products.

fgorga said:

Interesting work. Thanks for sharing.

A couple of chemical comments...

I would expect that the neutral triethanolamine, which exists at high pH, should complex iron much better than the positively charged triethanolammonium ion you make by adding acid to the TEA. If you are interested in the details of this chemistry, I can write out the equation... just let me know.

I would also be worried about the yellowing you observe in the last case. It is likely to get worse over time.

Amines, in general, will, even in pure form, go yellow or brown over time upon exposure to air. They oxidize to make a variety of products.

Click to expand...

I'd definitely be interested in the equations around it. I've been reading a few papers, one interesting one being "IRON-LIGAND ELECTROKINETICS TOWARDS AN ALL-IRON HYBRID REDOX FLOW BATTERY by KRISTA LEIGH HAWTHORNE" which discusses stability of iron hydroxide and TEA complexes. There was another paper I found somewhere about using TEA in a dying process as a moderating chemical to prevent ferric hydroxide staining. Plenty of things out there about TEA and iron, but not much in the realm of photography.

Yes, the yellowing I assume is due to ferric hydroxide. I'll try making a proper sodium acetate developer and see if it gives the same problem, but I expect my TEA-acetate solution just was not concentrated enough.

Yes, I know TEA and other amines can oxidize on exposure to air (though not particularly quickly) and will naturally turn yellow or darker colors. I haven't been able to find much at all about what these products would actually be. My understanding is it's not "junk" as in some polymerization type thing that is not reversible, but I can't find much other info

Also one interesting thing which happened upon standing overnight, my TEA-water developer initially was orange after development, but after sitting overnight is now a mild and transparent grey. I assume due to silver and iron in solution, with each one being reduced into metallic state. There was no precipitate at the bottom so it appears to be a colloid if thats the case.

earlz said:

Also one interesting thing which happened upon standing overnight, my TEA-water developer initially was orange after development, but after sitting overnight is now a mild and transparent grey. I assume due to silver and iron in solution, with each one being reduced into metallic state. There was no precipitate at the bottom so it appears to be a colloid if thats the case.

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So this TEA seems both a chelator and a strong reducing agent - it makes me wonder why does it not precipitate silver on contact with silver nitrate in the paper and cause fogging. Also could it also not at least reduce some of the unexposed ferric to ferrous, if not to metallic Fe, in the paper - giving rise to fogging as well. Or may be at room temperature, the reductive reactions are far slower than the "developer" function of coordination with the ferrous and take it up to silver nitrate to form the silver image.

Interesting stuff. I guess you will have to figure out the reuse/recycle/replenish protocol for TEA to be used as a viable and practical developer+clearing agent for kallitypes.

There are some mentions in the literature about making silver nano-particles with the use of TEA, by the way.

:Niranjan.

nmp said:

So this TEA seems both a chelator and a strong reducing agent - it makes me wonder why does it not precipitate silver on contact with silver nitrate in the paper and cause fogging. Also could it also not at least reduce some of the unexposed ferric to ferrous, if not to metallic Fe, in the paper - giving rise to fogging as well. Or may be at room temperature, the reductive reactions are far slower than the "developer" function of coordination with the ferrous and take it up to silver nitrate to form the silver image.

Interesting stuff. I guess you will have to figure out the reuse/recycle/replenish protocol for TEA to be used as a viable and practical developer+clearing agent for kallitypes.

There are some mentions in the literature about making silver nano-particles with the use of TEA, by the way.

:Niranjan.

Click to expand...

So I decided to actually test TEA+water with raw solutions and tiny coatings on paper. I don't understand the exact chemistry behind it, but here is what happens.

Adding silver nitrate to dilute solution of TEA+water: reveals pale brown precipitate which quickly goes into solution. Solution color: clear
Adding silver nitrate to alkalized (pH 14, sodium hydroxide addition) of TEA+water: reveals dark brown precipitate which goes into solution, but more slowly. Solution color: clear
Adding ferric sulfate (acid, undissolved powder in saturated solution) to dilute TEA+water: powder drops to bottom of solution. Enters solution very slowly. Adding very much will cause it to stop entering solution due to low solubility limit. Solution color: orange
Adding ferric sulfate to alkalized TEA+water: powder drops to bottom, quickly entering solution. Solution color: very pale green, with a lot of ferric sulfate addition, stays translucent without precipitate but turns darker blue-green
Adding a lot of ferric sulfate to non-alkalized TEA+water: solution remains orange and opaque with ferric sulfate powder settling to the bottom with standing.
Adding tiny amount of sodium chloride to alkalized TEA+water+silver nitrate+ferric sulfate: causes silver to immediately drop out of solution as a dark greenish grey powder. Does not reenter solution upon addition of thiosulfate nor additional TEA
Adding tiny amount of sodium chloride non-alkalized TEA+water+silver nitrate: Same result as alkalized with ferric sulfate
Silver nitrate paper added to sodium chloride + alkalized solution: orange silver on paper
Silver nitrate paper added to alkalized solution: paper remains perfectly white
Silver nitrate paper added to non-alkalized solution: paper remains perfectly white
Silver nitrate paper, made from non-ideal paper for kallitypes: paper turns orange (unsure what is actually in this paper). Solution is unaffected

It's really hard to make sense of what is really happening here, but TEA is definitely unique in its ability to precipitate some kind of silver compound from silver nitrate, only to then dissolve it again. I'd be super interested if anyone has an idea on the potential chemical equation happening here.

Regardless, this proves that TEA is a reasonable fog-free kallitype developer, but might benefit from an addition of alkali, going against pretty much everything taught about how kallitypes should be developed. Higher pH will result in more complexing ability with ferric compounds. I didn't test iron hydroxide because its such a mess to clean up, but I assume barely soluble ferric sulfate is a reasonable approximation. One risk of what could be happening here is reduction of ferric sulfate to ferrous sulfate, which is much more soluble, however at such a high pH that should also cause silver to fall out of solution so I think that even if this mechanism does happen, the silver compound generated is extremely resistant to reduction. Adding ascorbic acid+hydroxide in a less precise test caused silver and possibly iron to immediately fall out of solution as grey metal (creating a colloid, metal did not fall to bottom). Ferric oxalate (20% solution) seemed to do nothing when added to any of the solutions, solution remained clear with no precipitate. Also, the addition of sodium chloride causing a silver powder I believe is proof that this is not generating silver nanoparticles as may be indicated by some papers (I believe this requires a surplus of silver nitrate to do)

I made a few videos because I thought the reactions were pretty fun to observe

silver nitrate addition: Ferric sulfate addition: Sodium chloride addition:
Edit: also further evidence that the stuff to fall out of solution is mostly silver and not iron, it leaves a fine coating on glass ware after the sodium chloride addition. This could not be cleaned by hydrochloric acid which would have dissolved iron immediately. It did dissolve and was cleared however by addition of copper sulfate+sulfuric acid+sodium chloride bleach, and then for good measure rinsed and thiosulfate added. Afterwards beaker was spotless clean

This is a really great set of experiments - with a cinematic flair even!

I will raise some questions rather than making any definitive diagnosis, not being an inorganic chemist by any stretch of the imagination (Paging Dr. Ware!)

earlz said:

Adding silver nitrate to dilute solution of TEA+water: reveals pale brown precipitate which quickly goes into solution. Solution color: clear

Adding silver nitrate to alkalized (pH 14, sodium hydroxide addition) of TEA+water: reveals dark brown precipitate which goes into solution, but more slowly. Solution color: clear

Click to expand...

Perhaps AgOH (or subsequently Ag2O) formation followed by complexing with TEA?

earlz said:

Adding ferric sulfate (acid, undissolved powder in saturated solution) to dilute TEA+water: powder drops to bottom of solution. Enters solution very slowly. Adding very much will cause it to stop entering solution due to low solubility limit. Solution color: orange

Click to expand...

Hydrolysis to Fe(OH)3?

earlz said:

Adding ferric sulfate to alkalized TEA+water: powder drops to bottom, quickly entering solution. Solution color: very pale green, with a lot of ferric sulfate addition, stays translucent without precipitate but turns darker blue-green

Adding a lot of ferric sulfate to non-alkalized TEA+water: solution remains orange and opaque with ferric sulfate powder settling to the bottom with standing.

Click to expand...

Ferrous hydroxide is green - so may be ferric hydroxide reduction going on here with added alkali but not so with neat TEA?

earlz said:

Adding tiny amount of sodium chloride to alkalized TEA+water+silver nitrate+ferric sulfate: causes silver to immediately drop out of solution as a dark greenish grey powder. Does not reenter solution upon addition of thiosulfate nor additional TEA
Adding tiny amount of sodium chloride non-alkalized TEA+water+silver nitrate: Same result as alkalized with ferric sulfate

Click to expand...

Reduces silver chloride but not silver nitrate under these conditions? Could it make a good silver recovery process?

earlz said:

Silver nitrate paper added to sodium chloride + alkalized solution: orange silver on paper
Silver nitrate paper added to alkalized solution: paper remains perfectly white
Silver nitrate paper added to non-alkalized solution: paper remains perfectly white
Silver nitrate paper, made from non-ideal paper for kallitypes: paper turns orange (unsure what is actually in this paper). Solution is unaffected

Click to expand...

Seem fairly consistent with solution reactions. Non-ideal paper is buffered?


:Niranjan.