Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 69,879   Posts: 1,520,391   Online: 1018
      
Page 1 of 4 1234 LastLast
Results 1 to 10 of 31
  1. #1
    htmlguru4242's Avatar
    Join Date
    Aug 2005
    Location
    Sandy Hook, CT
    Shooter
    Multi Format
    Posts
    973

    -Another- Theoretical Question - Ferrogallate Process?

    Ok, my mind is going again, and I've another idea.

    <Long winded pre-explaination>
    Seeing something online about iron gall ink today reminded me that "invisible" ink could be made from iron gall (ferrogallate) ink. If one component of the ink is written onto the page, very little in terms of writing will apprear, however, if the other component is washed over, the text will be revealed after a short time.
    </long winded pre-explaination>

    I also realized that this ink only works with Fe3+ (ferric), not Fe2+ (ferrous) iron compounds.

    SO, if a light-sensitive iron compound (ferric ammonium citrate, ferric oxalate, etc., etc.) were coated onto a paper and exposed to light, therefore reducing some of the iron to ferrous, and the paper was then soaked in or coated with gallic acid / tannic acid / gallotanate, etc., would an image not be produced?

    Do I have a good idea, has this been done before, or am I WAY off?

  2. #2
    Donald Qualls's Avatar
    Join Date
    Jan 2005
    Location
    North Carolina, USA (transplanted from Seattle)
    Shooter
    Multi Format
    Posts
    1,845
    What you've described is the core of the cyanotype rex and chrysotype rex processes. With cyanotype rex, instead of mixing the ferric ammonium citrate and potassium ferricyanide solutions, the ferric ammonium citrate (or alternately ferric oxalate) are applied to the paper and exposed, producing (they say) a very faint print-out image, which is then developed with a wash of potassium ferricyanide (for cyanotype rex) or gold chloride solution (for chrysotype rex -- the used solution can then be used as a gold toner, they say, which helps ease the price issue a bit compared to $30 per print for the gold).

    With cyanotype, you're producing an iron based final image (Prussian blue, ferric ferricyanide IIRC). If you were to wash with gallic acid instead, you'd most likely get a ferric gallate image, with all the permanence of the iron-gall ink (and, as with the other processes, it would be a photographic negative). You likely would get something similar with tannic acid, pyrogallol, etc.; you'd essentially be creating a gallate version of a cyanotype.

    I don't recall reading about anyone trying this -- possibly because the two step, sensitize and develop process originating with Herschel was abandoned for the mixed sensitizer, printing-out processes for cyanotype, chrysotype, and kallitype before there were photographic negatives to print, and before anyone tried Herschel's original (much faster) method in camera.
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  3. #3
    htmlguru4242's Avatar
    Join Date
    Aug 2005
    Location
    Sandy Hook, CT
    Shooter
    Multi Format
    Posts
    973
    Good to know that this would [probably] work. I'd be surprised if nobody's tried this before, as everything seems to have been tried at one time or another (and everytime I come up with a good idea, it almost certainly turns out to have been done). Once I get my tannic / gallic acid extracted (another project), perhaps I'll try this. The only iron compound I have is yellow ferric ammonium citrate - is that light sensitive enough?

    was abandoned for the mixed sensitizer, printing-out processes for cyanotype, chrysotype, and kallitype before there were photographic negatives to print, and before anyone tried Herschel's original (much faster) method in camera.
    Is this to say that the two-step method is faster than the print out method, perhaps even in-camera fast? Or am I reading incorrectly?

  4. #4
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,911
    Images
    65
    Since these are all UV sensitive materials, there is little hope to get camera speed.

    There is no way to increase sensitivity of imaging systems based on non-crystal imaging. That is why silver halide crystals perform so well, you can increase their sensitivity of the crystal and move it into the visible range. No one has been able to do it for the other alternative systems.

    PE

  5. #5
    Donald Qualls's Avatar
    Join Date
    Jan 2005
    Location
    North Carolina, USA (transplanted from Seattle)
    Shooter
    Multi Format
    Posts
    1,845
    PE, not to argue, but the recent work on cyanotype rex has demonstrated in-camera negatives, cyanotype-to-cyanotype contact printing (through heavy paper), and exposure of prints with ordinary tungsten light. The very same chemicals are vastly faster (based on my reading, it looks like several stops faster) when the sensitive iron and the colorant are separated; my hypothesis (as a non-chemist) is that light energy goes to reducing ferric to ferrous without being soaked up in the secondary reaction or absorbed by its products -- which might reasonably mean both less energetic (i.e. longer wave) light can do the job, and a great deal less of it is needed.

    Of course, "in camera" is subject to interpretation, but I take it as meaning it's practical to make (possibly multi-minute) exposures in camera and produce usable negatives which can then be contact printed back to cyanotype for a positive. Even if the speed is more commensurate with Becquerel process Daguerreotypes than, say, collodion wet plate, it'd still be a useful alternative for some subjects and in some circumstances.

    HTML, I think you need *green* ferric ammonium citrate, same as for cyanotype. Mind you, I have no real idea what the difference is between the two, but everything I've ever seen (photographically) that called for ferric ammonium citrate specified the green. I haven't had a chance to try a rex-type cyanotype, but hope to do so in the next week or two (temporary change in schedule will reduce my time conflicts with my darkroom doing double duty as my wife's bathroom). Unlike others who've posted the prints here on APUG, I've attended no workshops, and been able to find no detailed information on line; haven't even been able to read Herschel's original work describing the process, so I'll be more or less reinventing it. Should be interesting. I might try developing one in strong tea if I get good results with the regular blue...
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  6. #6
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,911
    Images
    65
    Donald;

    I agree with your comment, but all things are relative.

    Camera speed is a little better than the 2 - 4 hours of exposure in daylight which is what cyanotype needs. If you improve that by 5 stops then you are talking about 7.5 minute exposures rather than 4 hours. This is still a long exposure time. A 5 stop increase is huge with this type of material, and spectral sensitization is still not possible AFAIK, so it is a very limited system.

    That was my whole point. It will always seem like you can almost get there from here, but not quite. I worked with light sensitive copper systems for quite a while and got up to about Kodabromide speed with cuprous oxide. Then it just ran out of steam. I could never get exactly what I wanted from it and eventually had to give up. It was very discouraging.

    PE

  7. #7
    htmlguru4242's Avatar
    Join Date
    Aug 2005
    Location
    Sandy Hook, CT
    Shooter
    Multi Format
    Posts
    973
    For my purposes, I consider anything less than about 10 minuntes in bright sun as practical for in-camera. Sure, this isn't anywhere near what you can get from even enlarging paper (which can be much less than a second in full sun), but it's still useful.

    Is "cyanotype rex" simply the same formula as the regular cyanotype, but just with the paper coated with citrate first, and then ferricyanide after exposure? Or is there a different chemistry requirement?

  8. #8
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,911
    Images
    65
    My comment did not account for f stop. That range I gave was merely a typical exposure in a contact frame. Use of a lens or pinhole camera will change the exposure by quite a bit, but I would have no idea by how much.

    PE

  9. #9
    Donald Qualls's Avatar
    Join Date
    Jan 2005
    Location
    North Carolina, USA (transplanted from Seattle)
    Shooter
    Multi Format
    Posts
    1,845
    PE, I routinely get cyanotype exposures in (North Carolina) summer sun that run from ten to fifteen minutes (in a contact frame, under a 9x12 cm negative developed to "normal" large format contrast). This is with traditional cyanotype made from the Formulary kit. That would suggest that C. rex would be too fast to expose this way with sunlight; I'd *have* to expose it under some kind of artificial source, lacking a neutral density filter for blue/UV light. Given the reported difference in speed, it might be that reports of non-UV exposure are simply because the stuff is fast enough to expose in the very low level of residual UV in light sources normally considered UV free (like common tungsten/argon lamps, near-sunset sunlight, etc.). Even so, that would make it practical for much of what I want to do with it, such as enlarge to C. rex (with a cold light, there ought to be significant UV from the tube in comparison to a tungsten enlarger source).

    And as one who makes a fair amount of pinhole photographs, a multi-minute exposure doesn't seem terribly impractical (though it's an awfully long time for a portrait). According to those who've developed C. rex, the light level inside a camera (at an unspecified f-stop) isn't much different from that outside, which seems a bizarre result to me (but I've never yet put a light meter to the ground glass in my 4x5, it just *seems* a lot dimmer even with an f/4.5 lens wide open).

    In any case, HTML, as far as I've been able to determine from my reading, that's exactly right -- coat with the green citrate solution (a little weaker than that normally used to mix cyano sensitizer, I think, though I wouldn't expect stronger solution to be a bad thing), expose until a faint image prints out, then develop with your choice of several solutions to produce cyanotype rex, chrysotype rex, kallitype, a platinum/palladium variant, or possibly the ferrogallate print you started this thread asking about (this is largely guesswork on my part, since the details of the rex processes aren't yet published -- the creators understandably wanting to make back at least some of their development materials costs on the $30/print gold process by selling the PDF and workshop slots before letting the process out for unlimited use from which they'll never see another dime). The originators suggest you get a "finer" print by using ferric oxalate instead of ferric ammonium citrate, but the citrate is faster.

    I agree, PE, on your "almost get there from here" comment. There's a good reason silver processes "won" in the mid-19th century, and it wasn't because silver was cheap then (it was, and is, a precious metal, just not anything like *as* precious as gold or platinum) -- just that of the available chemistries, silver halide lends itself best to fine tuning from a bunch of different directions. I'd bet you could (with a century of research) do much the same with selenium, but it's both a lot more toxic than silver, and harder to work with (and a lot less common, at least in easily extracted form, moreso in the 19th century even than now); same for cadmium on all counts. However, for those of us on a limited budget, cyanotype rex is a lot more accessible than anything that requires buying silver nitrate in quantity greater than a few grams at a time (and the chemicals don't require hazmat releases, "statements of intent" for the "hazardous oxidizer", etc.).

    OTOH, I have the cyanotype chemicals on hand, plenty of paper and negatives to print, and a darkroom to work in where I can avoid fogging the rex if it is that much more sensitive than "traditional" cyanotype (red safelight isn't going to fog the stuff, I'm betting, even if it's fast enough for enlargements). And for the next two weeks I have reduced schedule conflicts, so I should be able to experiment a good bit...
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  10. #10
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,911
    Images
    65
    Donald;

    I cannot comment on the 'rex' processes not having used them. It just seems strange to me that they would pick up speed beyond the UV range. I don't dispute it, but if I ever get to doing it, I have a spectrosensitometer to test the materials with to see what is going on.

    As for Selenium and Cadmium, I think that Se will be just fine as a material to generate electricity from sunlight and Cd due to toxicity is safely left on the shelf. But, there is quite a gem of truth in your comments about these two elements.

    After all, if cuprous oxide works, what else is out there. I think that the field is open for a good investigator and suggest that you look for the book by Khosar or Kosar, I forget the spelling OTOMH. Fascinating book on alternative processes. I have read it cover to cover and unfortunately have forgotten most of it due to disuse and time. Everyone wanted Ag emulsions and not these 'old fashioned' dinosaurs. (well, now here we are with 'rex')

    Best of luck with your trials, I'm working with cyanotypes myself right now, trying to tweak some things.

    PE

Page 1 of 4 1234 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin