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  1. #21
    Photo Engineer's Avatar
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    Quote Originally Posted by fparnold
    PE

    Do you have any suggestions in the open literature concerning the copper-oxide system? J. Phys. Chem. B would be fine. :~)
    AFAIK, no publications were made externally on this subject. There might be a research disclosure, but no patent issued. I was not the originator of this idea anyhow, I just worked on it as one of the team members.

    Basically, it was cuprous oxide precipitated in the dark in a peptizing polymer and then coated. Exposure was normal (blue + uv light) and development was done with sulfuric acid at about 0.1 N. The image could be fixed with sodium hypo.

    Hope that helps. It is just OTOMH, and very sketchy now after all of these years.

    PE

  2. #22

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    Thanks. I'm doing some work on organic photosensitizers for wide-gap inorganic clusters, so this sounded potentially interesting.

  3. #23
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    precipitated in the dark in a peptizing polymer and then coated.
    I'm probably just not recognizing the word, but what is a "peptizing polymer"?
    Last edited by htmlguru4242; 02-28-2006 at 08:32 PM. Click to view previous post history. Reason: spelling errors spelling errors

  4. #24
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    Quote Originally Posted by htmlguru4242
    I'm probably just not recognizing the word, but what is a "peptizing polymer"?
    Gelatin is a peptizing polymer.

    When silver halide is precipitated in its presence, the silver halide crystals are 'peptized' by the gelatin polymer by being surrounded and suspended by the gelatin. If this were not so, the crystals would settle to the bottom of the container. The gelatin suspends the crystals evenly within the solution.

    Gelatin cannot be used with cuprous oxide as it is dissolved in strong acid then precipitated in strong base and this pH cycle destroys the gelatin.

    PE

  5. #25
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    I took a look on The Unblinking Eye, and sorry, I remembered wrong. There are no cyanotype recipies that have gallic acid. A number of them have tannic acid. You could try them. I don't think that they promise any increase in speed. Hope that helps.

    On a slightly different tangent, along with the copper oxide, has anyone thought about/experimented with replacing the silver nitrate in the Vandyke formula with copper nitrate? Following a chemical line of reasoning, copper is slightly more reactive than silver, and should thus be able to facilitate the reduction of the iron.

    Drew
    "But what is strength without a double share of wisdom." --John Milton

    "Our greatest fear should not be of failure, but of succeeding at something that doesn't really matter." --Unknown missionary

  6. #26
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    There are no cyanotype recipies that have gallic acid. A number of them have tannic acid.
    Yes, I just found these, actually, thank's for pointing in that direction. I don't think that the tannic acid / gallic acid difference would really matter, they seem to be similar enough ...

    On a slightly different tangent, along with the copper oxide, has anyone thought about/experimented with replacing the silver nitrate in the Vandyke formula with copper nitrate?
    Well that would make it a tad cheaper ... hmmm

  7. #27

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    Quote Originally Posted by Dracotype
    On a slightly different tangent, along with the copper oxide, has anyone thought about/experimented with replacing the silver nitrate in the Vandyke formula with copper nitrate? Following a chemical line of reasoning, copper is slightly more reactive than silver, and should thus be able to facilitate the reduction of the iron.
    My gut instinct is that this won't work because most copper(I) salts won't dissolve in water without decomposition. Copper(I) compounds are strange beasts. They are very good reagents for certain reactions in organic chemistry where they seem to "carry" certain anions very well.

    Copper as a metal is certainly "more reactive" than silver as a metal, but we are concerned with the salts here. Besides, isn't the Vandyke reaction basically a Fe(II)->Fe(III) / Ag(I)->Ag(0) couple? (the initial Fe(II) being produced by photo-reduction of Fe(III) ammonium citrate) Maybe I'm getting mixed up here.

  8. #28
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    I did remember one reference. Peter J. Hillson of the EK Harrow labs may have published some work on light sensitive copper systems.

    PE

  9. #29
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    Well, I got a chance, yesterday and today, to try a few cyanotypes using what I understand to be the rex methodology. Here's what I did, and what I got for results.

    I used my existing cyanotype A solution, 200 g/L green ferric ammonium citrate in distilled water; the bottle was mixed around 18 months ago, and has been opened and small amounts used a number of times (in case that makes a difference). For each print, I coated 1 ml of this solution onto a 4 1/2 x 6 inch piece of Montval "Brut" (rough) watercolor paper. Prints were coated with a foam brush and dried under red safelight, some with a hair drier and others allowed to dry naturally.

    Each print was exposed in mid-afternoon sun, yesterday in full "Sunny 16" conditions, today in "Hazy" to "Cloudy Dull" with an average of "Cloudy Bright" for most exposures. Full sun gave a dim printed out image (darkening of the citrate from yellow, as dried, to light brown) in about three minutes; dimmer conditions took five (this is at least two, probably three stops faster than the mixed solution consisting of equal parts of the above A solution and the B solution, 50 g/L potassium ferricyanide). The exposed print was then "developed" by brushing on approximately 1 ml of the ferricyanide solution (mixed at the same time, stored under the same conditions, and used a similar number of times to the A solution above), and either washed immediately or allowed to air dry before washing. Darkening of the exposed areas was immediate on contact of the ferricyanide solution, like a Disney animation of painting an image with a flat brush. I also attempted developing one print in a tray with about a pint of water and a few ml of ferricyanide solution added (roughly equivalent to 150-250 mg/L), and while some development took place, the image washed off faster than it formed (the solution was also dissolving both the exposed and unexposed citrate).

    I found best results came from drying the print after "developing", then giving first wash in a tray containing about a pint of distilled water acidified with about 1/4 tsp of Kodak Indicator Stop Bath concentrate (to ensure against alkalinity in the paper, mostly). Second wash was in tap water until all yellow sensitizer was washed out. Prints are still darkening (oxidizing), but the best prints look as good as my best cyanotypes did at this stage (aside from brushing artifacts that appeared in development).

    What I need at this point is a means of applying the developing solution evenly, without brushing away the surface reaction products or having them wash off in a tray of solution, both of which reduce density and muddle the image. I may need to optimize concentration of the solutions, but just this level of simplicity indicates the process can be two to three stops faster than the way it's usually done, with quality of results that's at least as good.

    That said, what I have (so far) is nowhere near matching the claims made for cyanotype rex relative to speed, and far from being partly or largely independent of UV (hence why exposure only increased one stop when the light was two stops dimmer -- clouds reduce UV much less than visible light). Of course, the progenitors of cyanotype rex have invested hundreds of hours of lab time in developing the process (in parallel with chrysotype rex, which surely represents most of their incurred cost at $30 per 8x10), and I've put in (so far) about three hours, some of that spent watching sensitized paper dry.

    We'll see what I get in future sessions...
    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. #30
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    Quote Originally Posted by Donald Qualls
    I used my existing cyanotype A solution, 200 g/L green ferric ammonium citrate in distilled water; the bottle was mixed around 18 months ago, and has been opened and small amounts used a number of times (in case that makes a difference). For each print, I coated 1 ml of this solution onto a 4 1/2 x 6 inch piece of Montval "Brut" (rough) watercolor paper. Prints were coated with a foam brush and dried under red safelight, some with a hair drier and others allowed to dry naturally.
    Thanks for posting your experiment. I think that the alternative print community benefits from a free and open exchange of methods and experiments. Plus it keeps us from all repeating the same mistakes .

    The increase in speed might be more significant if the oxalate salt of iron was used, but I have no data on this. Only a suggestion.

    I think that the traditional method for cyanotypes shows an advantage when it comes to development. The two solutions are on the paper. With brushing on the ferricyanide, you open the possibility of uneven development. Perhaps if you had a super saturated solution of potassium ferricyanide that you developed your print in? That might take care of washing away the ferric ammonium citrate to early. Just a suggestion.

    Drew
    "But what is strength without a double share of wisdom." --John Milton

    "Our greatest fear should not be of failure, but of succeeding at something that doesn't really matter." --Unknown missionary

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