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  1. #1

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    What causes Wet Tintype to appear positive?

    The wet collodion process, when used to make ambrotypes (on glass) or Tintypes (on black japanned metal). I know it is actually developed as a negative, and then appears as a positive against a dark background. My question is this....what is it about the process that allows the developed silver compounds to appear lighter than they do on modern negative materials? Is it the developer, the actual silver compounds or the "cyanide" type fixer? (or a combination?) In general, what contributes to allow the developed/fixed image to appear light enough to "read" against the dark background?

  2. #2
    rwyoung's Avatar
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    You can sometimes get the same effect with thin negative on "modern" materials. To me, it seems like the thinnest portions (those that would appear black) simply show the background. A bit more silver and you get less background showing through and a bit more light reflected from "behind" the viewer. More silver, more reflection, less background showthrough.

    Funny thing is, I've tried to do this with 4x5 film and sometimes it works great, other times it didn't work for a damn. Probably mostly my technique and not controlling all the variables properly.

    And I've found a few old dry glass plate negatives that exhibit the same phenomenon but they also showed considerable "metalization" of the silver, probably due to incomplete fixing and the silver bonding with sulfur, etc in the atmosphere.

  3. #3
    JG Motamedi's Avatar
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    There is something about the reaction between the FeSO4 developer and the silver salts which forms white or metalic silver crystals rather than the black crystals seen on modern B&W materials. I have tried to use other developers with collodion (notably pyro) and never obtain good positives.

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    htmlguru4242's Avatar
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    This effect is visible on modern films that are grossly underexposed, underdeveloped or both. I'd venture to guess that it's because the small number of silver crystals reflect some light rather than block it as it would at the proper density.

    Its interesting though how its so pronounced on tintypes. I've tried this with 4x5 film many times, and have never gotten a good effect.

    ONCE I got an excellent positive, but it was completely accidental. I was shooting Efke KB25 at night. The exposures were very long, and most came out well. I accidentally closed the shutter too early on one exposure, and when developed, it didn't look like much was there. However, when I put it against a black paper, and angled it at about 45 degrees, a very clear and detailed positive was evident in the brighter regions of the shot.

  5. #5

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    FeSO4 developer

    Quote Originally Posted by JG Motamedi View Post
    There is something about the reaction between the FeSO4 developer and the silver salts which forms white or metalic silver crystals rather than the black crystals seen on modern B&W materials. I have tried to use other developers with collodion (notably pyro) and never obtain good positives.
    Have you tried the Iron developer with modern negative materials to see if there will be the correct look?

  6. #6
    JG Motamedi's Avatar
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    Quote Originally Posted by PHOTOTONE View Post
    Have you tried the Iron developer with modern negative materials to see if there will be the correct look?
    No, I haven't, but I will put it on the list of things to try. I will let you know if I ever do so.

    If you or anyone else wants to try, the recipe is pretty simple:

    500ml Water
    17g Ferrous Sulfate
    13ml Alcohol
    16ml Glacial Acetic Acid

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    direct positive

    I do not know exactly what the reason is for collodion positives but I have been experimenting with gelatin emulsion and making direct positives on glass and trophy aluminum using dektol developer with ammonium thyocanate added, or potassium thyocyanate(does not have an ammonia odor).
    The images have a little less contrast than I would like but I have made and seen plenty of good collodion images a bit on the soft side.

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    The effect is from viewing negatives by way of reflected light rather than the transmitted light they are normally designed for. Remember we're suing silver here so it IS reflective, or at least more reflective than a black backing like ambrotypes are put against or the japanned laquer of a ferrotype.

  9. #9

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    Quote Originally Posted by Christopher D. Keth View Post
    The effect is from viewing negatives by way of reflected light rather than the transmitted light they are normally designed for. Remember we're suing silver here so it IS reflective, or at least more reflective than a black backing like ambrotypes are put against or the japanned laquer of a ferrotype.
    Yes, yes, but but you can put a thin sheet film negative against a black background and it is barely visible, because the silver in the emulsion does not reflect much light, whereas a tintype can look quite clear and snappy. So does a well made ambrotype. I understand the concept that the negative appears positive when viewed against a darker background, it is just that a wet collodion tintype or ambrotype had a developed image that reflects much more light thus giving it more tonal range and snap. A modern sheet film negative processed in modern mq developers reflects almost zero light, so, when placed against a black card or felt, there is no snap.

  10. #10

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    Ferrotypes and ambrotypes are also usually developed with a developer that heightens the reflectivity, I believe. I'm sure you could do the same with sheet film with a high silver content if you wanted.

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