wetplate question for chemists

Discussion in 'Alternative Processes' started by smieglitz, Feb 5, 2006.

  1. smieglitz

    smieglitz Member

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    I took up wetplate collodion a few months ago and have recently run into some contrast problems with it. Part of these problems might be resolved by using potassium cyanide as the fixing agent but I am hesitant to use that chemical because of its toxicity and issues of storage. The historical alternative has been sodium thiosulphate in about a 20% solution.

    I'm wondering if ammonium thiosulphate might be substituted for the regular hypo without ill effect. This question has been posed on other (wetplate) forums and the response by practitioners is generally: "Why take a chance? Use the traditional method..." I'm wondering if the rapid fixing agent might produce a brighter, higher contrast image more like the effect of the KCN. I can of course test the chemical fixing potential by running a plate through it, but I'm wondering about issues of longevity, stability, etc.

    AFAIK, the wetplate emulsion is a combination of silver iodide and silver bromide salts formed by the reaction of a silver nitrate bath on cadmium, potassium, and ammonium iodides and bromides in the "iodized collodion." Anything here that might be problematic (w.r.t. color, archivalness, tonality, etc.,) if ammonium thiosulphate was substituted as the fixing bath?

    Any insight appreciated.

    Thanks,

    Joe
     
  2. Aggie

    Aggie Member

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  3. smieglitz

    smieglitz Member

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    Aggie,

    Thanks for the pointer. I'm aware of that forum (and others) but I am seeking the insight of scientists rather than practitioners. I'd rather not pose this question on either wetplate forum for various reasons.

    I'm hoping someone here with a background in chemistry might provide general information on what to expect if I substituted ammonium for sodium thiosulphate in the wetplate process.

    Joe
     
  4. Ole

    Ole Moderator Staff Member Moderator

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    All I can say is "give it a try".

    I have seen with other old processes that ammonium thiosulfate tends to bleach the image a little, the finer-grained the image the more it bleaches. So with POP, VDB and lith prints I sometimes use a little of it if I want to clear the highlights.

    Since cyanide has an even greater affinity for silver than thiosulfate does, I would expect it to have the same effect - only more.

    There should be no problems with image stability or longevity when using ammonium thiosulfate instead of sodium; and it's much better than potassium cyanide with regards to photographer longevity.

    You could try a "rapidized" sodium thiosulfate: Add a little ammonium chloride to the sodium thiosulfate. My OF-1 fixer is based on this, and works fine with most silver processes (and clears the highlights in POP and lith prints almost as much as TF-4).
     
  5. smieglitz

    smieglitz Member

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    Thanks for the info Ole. A slight bleaching effect may be just what I'm looking for to clear some veiling on ambrotypes.

    Joe
     
  6. Kerik

    Kerik Member

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    Joe,

    You probably know this already, but I've read/heard that one of the risks of non-cyanide fixers is that there is a risk of the collodion emulsion shrinking and cracking over time. I have no idea weather this is true or one of those things that gets passed down without evidence. I'm using HCN for fixing and I think with a little care it can be used safely.
     
  7. Donald Qualls

    Donald Qualls Member

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    I think you're deeply confused -- possibly dangerously so, Kerik.

    HCN is a gas at room temperature, or when dissolved in water forms Prussic acid; it's the gas generated when potassium cyanide or sodium cyanide contact acids, and is the active ingredient in the gas chambers used to execute criminals.

    For fixing wet collodion emulsions, KCN, potassium cyanide, is your chemical -- it's still hazardous, in that it will evolve hydrogen cyanide if it contacts acids, but it's not automatically deadly like HCN is in quantities above the lowest concentration you can smell. I would note that in a demo video I've seen of wet collodion tintype making, the KCN fixing step was done outdoors, after development was completed and the plate had been washed to remove all traces of the (acidic, ferrous sulfate based) developer. Given the rapidity with which you must work in wet plate, I'd say cyanide fixer is more hazardous than it needs to be if thiosulfates will do the job.
     
  8. smieglitz

    smieglitz Member

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    And so I did today.

    I tried Sprint ammonium thiosulphate-based fixer concentrate diluted 1+2 with water. I figure this is about a 15% concentration. (I called the copmpany but was told the formula was proprietary and they couldn't disclose the actual concentration-Kodak's MSDS for their Rapid Fixer part A listed ammonium thiosulphate content as between 40-50% so I'm basing my guess on that figure.)

    Here's the test ambrotype on black glass. It took about 15-20 seconds to reverse the image and clear the plate which is much quicker than hypo. I also think the image appears a little bit warmer than when I use the sodium thiosulphate.

    I was very pleased to see this result.

    Joe

    [​IMG]
     
  9. JG Motamedi

    JG Motamedi Member

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    Joe,

    There was a post somewhere on Bob Szabo's CW forum about using Ammonium Thiosulphate as a fixer. Unfortunately after changing software much of that forum's history is gone. As I recall, the gist (once it went beyond the "use the traditional method...") was that you could use ammonium thiosulphate with no major repercussions. Maybe once I work through the 25kgs of sodium thiosulphate I recently bought, I will give it a try too...
     
  10. smieglitz

    smieglitz Member

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    25kg!!! You can spike a lot of aquariums with that.

    Ok. But hurry up. It is so lonely here in Farbyland. LOL.

    What a great word - "farby."

    Joe
     
  11. JG Motamedi

    JG Motamedi Member

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    I wish I had more uses for the word (or even the concept), but I am afraid that I am too deeply entrenched...

    jason

    ps: Pool supply stores can be a good source of very cheap hypo.
     
  12. Kerik

    Kerik Member

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    Donald, thanks for your 'concern', but I'm not confused. You are simply ignorant of my working practices. Maybe you could have asked before you started talking out of your behind.

    I'm aware of all the hazards of working with HCN that you describe. In my day job, I've been trained in the use of PPE for handling hazardous materials. When I'm working mobile (out of my camper darkroom), I fix outside. In my home darkroom I fix in front of a 400 CFM exhaust fan and wear a respirator. The 200 ml of 1.5% HCN solution is in the tray for a total of 20 seconds, then it's back in the plastic storage bottle. And, I know full well that the plate has to be completely rinsed of the acidic developer prior to fixing. hmm-K?
     
  13. colrehogan

    colrehogan Member

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    Nice image, Joe. Was this the effect you were looking for? Sorry I'm not familiar enough with the process to even attempt to answer your question regarding the chemistry. I'm still trying to learn about it myself.
     
  14. smieglitz

    smieglitz Member

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    Diane,

    I ran into problems with fogging the other day that I thought were related to the sensitizer and developer being at very dissimilar pH values. The attachment shows the difference between the test plate of the mannequin after I adjusted the pH and a detail of a portrait from earlier last week. Both were done on black glass with the same light, and lens.

    The gray veiling that is evident on the portrait is what I was trying to get rid of. The mannequin shot from yesterday has much better contrast and is also warmer, both effects which are desirable. The mannequin image had the sensitizer and developer at roughly the same pH and I used an ammonium thiosulphate-based fixer on that plate for the first time. It cleared and reversed the image in about 15-20 seconds which was much quicker than plain hypo and in about the same time as the KCN would act.

    So, the test plate chemistry changes did what I was hoping.

    Joe
     

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  15. Jorge

    Jorge Inactive

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    The problem is in your nomenclature Kerik. Hydrogen Cyanide is a gas at room temperature and it is fatal at low concentrations. You are using Cyanide salts, which if kept away from strong acids are perfectly safe to handle if you use the appropiate precautions.

    While you might think this is nitpicking, I think this is one instance where the right information and nomenclature are used. After all we dont want people trying to make Hydrogen Cyanide to fix their wet plates......
     
  16. Kerik

    Kerik Member

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    Jorge,

    D'oh!!!! Thanks for pointing out my error. I now see that I made a typo in my first post, then it got perpetuated. I use POTASSIUM cyanide (KCN), NOT hydrogen cyanide (HCN). I should have spelled it out rather than fat-fingering the abbreviation. So, Donald, perhaps that's what you meant by being confused. I'm not confused, but I am a crappy typist.

    In any case, I suppose I should emphasize that no-one should delve into processes like wet plate, daguerrotype or anything involving dichromates without understanding the hazards and proper handling of these materials. I apologize for any confusion I may have induced.
     
  17. Kerik

    Kerik Member

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    Joe,
    Do you think it was the pH adjustments or the change in fixer that resolved your problem? I went through serious fogging and veiling issues in the fall, as you probably recall from Quinn's forum. I started making plates again this week and everything is working very well (probably just jinxed myself by saying that). No fogging and very clean plates - no oysters or other funkiness happening.
     
  18. colrehogan

    colrehogan Member

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    Glad you got it sorted out, Joe.
     
  19. smieglitz

    smieglitz Member

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    Kerik,

    I think it was the pH adjustment that caused the improvement. The plates appear warmer than before and that might be a result of the fixer change, but I'm not sure as the silver tank and developer also were changed at the same time.

    I think the oyster problem is obviously related to the cleanliness of the plate but I also think using whiting gets some of it into the silver bath and raises the pH of that solution. I can never seem to get all the whiting off the edges of the plate and if I mess with it enough to do so, I usually end up touching the clean surface of the plate which means I have to reclean it with whiting which sticks in the edges of the glass and gets into the silver bath...

    So, I'm hoping a diffent cleaning routine along with the pH changes will alleviate most of the problems I've been having with the plates. The Rapid Fixer is just more convenient and quicker, but if it is also warmer, that would be a welcome benefit.

    The best plates I ever produced were done dripping nitric acid and potassium nitrate into the developer so I think the lower pH really does help produce more fog- or veil-free plates.

    Plese refresh my memory as to how you alleviated the fog problem you had.

    Joe
     
  20. Kerik

    Kerik Member

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    Joe,
    I've only used Rottenstone for cleaning, and it seems to work well and residue is easily removed. I got it from a local boutique woodworkers shop. I'm 90% sure after many tests that I had either a contaminated or erroneously labeled can of EE.
     
  21. JG Motamedi

    JG Motamedi Member

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    I am not so sure that there is really much difference between rottenstone and whiting. After all, they are both essentially calcium. However, in my use I have noticed that whiting appears to clean slightly better, but at the same time its residues (being white) are more noticeable. I actually had more problems with fogging when I was using rottenstone.

    Just a thought: It would be a lot of fun someday to hold a wet-plate conference/get together. The CW crowd have their "jamboree" every year at John Coffer's place way out in Dundee, NY (and I am sure we would be welcomed), but I often feel that our (if I can lump us all together) or at least my non-technical needs are often quite different. Perhaps I should post idea on Quinn's site.
     
  22. smieglitz

    smieglitz Member

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    I'd certainly be up for a conference. I'm also hoping I'll be invited to John Coffer's Jamboree in July after my Memorial Day weekend workshop with him in Dundee. I'm somehow hoping to stretch my trip to Peters Valley for your dag workshop into the Jamboree a week or so later, maybe visiting some friends on the east coast and then photographing my way back home at a leisurely pace.

    Here's another thought I've been kicking around related to oysters and such: I'm wondering if somehow taking a whetstone over the glass edge is creating a multitude of little pockets for whiting or small glass chips to collect in which ultimately form nuclei for oysters and comets. I'm going to try chemically cleaning the glass and then just subbing the edge with albumen rather than dulling the edge first with a stone and using whiting to clean it.

    Joe
     
  23. boyooso

    boyooso Member

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    I am curious, When you say 'black glass' it it really black glass or painted glass or glass backed with a black something?

    Thanks,

    Corey
     
  24. Kerik

    Kerik Member

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    Black glass. Available from stained glass suppliers. Most people seem to be using Spectrum 1009S Cathedral Glass. It's the kind...
     
  25. Donald Qualls

    Donald Qualls Member

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    Okay, you're using potassium cyanide -- hazardous, but not unmanageable. If you'd read all of my post, you'd have seen me spelling it out a couple times, in a manner that should have made it clear which one I was referring to in which context.

    Bad typing is less hazardous *to you* than chemical confusion, but could be just as bad to someone coming in late, as it were (though I agree that anyone starting to learn wet plate had better have their act together -- collodion, ether, and cyanide are all pretty hazardous to work in a closed room; darkrooms used to burn down pretty regularly when wet plate was *it* and safelights had a candle inside).

    And in between then and now, I've been corresponding on a mailing list with a guy who thinks it'll be perfectly okay to machine the cylinder of his black powder revolver to take modern smokeless cartridges. Please pardon my reaction -- I'd rather jump on someone who's doing it right than read a headline about someone I didn't jump on...