Kallitype Fading

Discussion in 'Alternative Processes' started by kq6up, Mar 31, 2011.

  1. kq6up

    kq6up Member

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    I am reading the Kallitype article on the unblinking eye site. The seem to mention that they will fade if not toned due to the silver oxidizing. Why would silver oxidizing fade the print. Isn't silver oxide black too?

    Thanks,
    Chris Maness
     
  2. R Shaffer

    R Shaffer Member

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    There is a fair amount disagreement about fading with modern kallitype methods, its mostly a bad rap they got in the early days (IMO). If your planning to sell your prints, then you may want to tone them for peace of mind. I think that if you develop and clear your prints carefully they will be around for a very long time.

    If you want to know more about why kallitypes fade then take a look at Dr. Wares article here

    http://www.mikeware.co.uk/mikeware/Argyrotype_Process.html

    Another good source for kallitype info is here

    http://www.bostick-sullivan.com/articles/kallitype.html
     
  3. Marco B

    Marco B Member

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    You are mixing up the chemistry terms for redox reactions (oxidation = atom loosing electrons, reduction = atom gains electron), with a possible oxidation product (silver oxide).

    When silver is oxidized in fading, silver atoms loose an atom and become mobile ions :
    Ag ---> Ag+ + 1 e- (electron)

    In most cases, the ion moves away from the original silver particle, and redeposits either as smaller silver particles after being reduced back to Ag, or reacts with sulphur in the air to produce stable silversulphide (Ag2S).

    In both cases, the original oxidation of the silver image, leads to a loss of density of the original image, and discolouration, as the smaller silver particles of the secondary products (whether Ag or Ag2S), reflect light differently and hence have a different color.

    A recommended article about all this is Gawain Waever's "A guide to fiber-base gelatin silver print condition and deterioration"

    Marco
     
  4. Vlad Soare

    Vlad Soare Member

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    Oxidizing is not about forming oxides, but about increasing the oxidation state by losing electrons. Silver oxide is just one of many possible oxidation products.
    Speaking of this, I must say I don't quite see why silver is (or at least was) considered a noble metal. It seems far from noble (in a chemical sense) to me. It oxidizes if you just look at it crossly. :smile:
     
    Last edited by a moderator: Apr 1, 2011
  5. artonpaper

    artonpaper Subscriber

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    Speaking of this, I must say I don't quite see why silver is (or at least was) considered a noble metal. It seems far from noble (in a chemical sense) to me. It oxidizes if you just look at it crossly. :smile:[/QUOTE]

    I once described silver, in a talk I gave on alt printing, as a drunk who would go home with anyone at the party. I have kallitypes that I made about 15 years ago, untoned, that are fine. I have seen some VDBs from the same period fade.
     
  6. Jim Noel

    Jim Noel Member

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    A properly made kallitype will not fade. Some developers seem to contribute to fading, and certainly incomplete clearing will do so. My 20 year old untoned, as well as toned ones show no sign of fading. There are some statements in Stevens book which led people down an incorrect path and subsequent fading. There have been several threads discussing this on this forum as well as alt photogrpahy.
     
  7. kq6up

    kq6up Member

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    I can see the print changing color due to the formation of Ag2S. I have had some negatives that I left hanging in the Sun for a long time turn from black and clear to yellow and clear. It was kind of an experiment.

    I was unaware that silver ions are mobile in a gelatin emulsion. Maybe PE could chime in here.

    I am a high school chemistry teacher, and I have had an ongoing discussion with a coworker (he has a Phd in Chem) as to weather silver in a silver gelatin print is atomic silver or silver oxide. I am under the impression that it is atomic silver.

    Thanks,
    Chris Maness
     
  8. Vlad Soare

    Vlad Soare Member

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    In an untoned silver gelatin print the image is made of elemental silver.

    I don't think they are literally mobile. What happens is that a silver ion has a positive charge, so it attracts an electron from a nearby silver atom. This second atom becomes a positive ion, attracting an electron from another atom, and so on. The ions don't really move. It's the distribution of the electrons that changes, so that an ion in a certain location can give birth to another ion in a completely different location, without actually moving at all.
     
    Last edited by a moderator: Apr 8, 2011
  9. Marco B

    Marco B Member

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    Why wouldn't silver ions potentially be mobile? There is lots of stuff that is capable of diffusing through gelatine layers. In fact, some of the photographic processes actually rely on such diffusion, think of Polaroid or Fuji instant film.

    Please see page 11 of the document by Gawain Weaver I referenced before, it is published by the George Eastman House and the Image Permanence Institute, part of Rochester Institute of Technology.

    I guess these institutes know what they are talking about :wink:

    Gawain literally writes:

    "Nearly all image decay begins with a single step: the oxidation of the image silver into silver ions. The developed silver image is composed of particles of silver metal (see Figure 1). When silver from these particles are oxidized, they become silver ions (Ag+).
    Unlike the silver metal (Ag), these silver ions are able to move within the gelatin.
    Thus, small dense image particles become larger clouds of even smaller particles. This oxidation and migration of silver atoms is the first step in image decay (Figure 16)."
     
  10. kq6up

    kq6up Member

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    Thank you. That answered my question very well.

    Chris Maness
     
  11. nworth

    nworth Subscriber

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    A properly cleared and fixed Kalitype should be quite stable. Some practitioners, particularly the early ones, were not very careful about these steps, and the results could be very unstable. Still, the silver image in Kalitypes is more delicate that that in silver-gelatin prints, and it is probably more subject to attack by things in the atmosphere and in the paper. Careful choice of paper for archival stability will certainly help. Gold or platinum toning is definitely recommended (selenium may work, too). Treatment of the print with various varnishes that are available now is a possibility, but it really hasn't been tested.