PMK intensification

Discussion in 'Large Format' started by joe_freeman, Aug 13, 2002.

  1. I can't get my negatives to intensify. I have Bergger BPF 200
    developed in PMK with a pinch of amidol, stopped in water, fixed in a
    non-hardening fixer. I underdeveloped about a zone and tried to
    intensify with selenium, but with no apparent change. I first tried
    it diluted 1:4, then 1:2, then straight. The negative was in each of
    the baths with constant agitation for five minutes. I thought I was
    going to pass out when it was in the straight bath. Selenium is some
    potent stuff. If anyone has some suggestions or ideas, I'd really
    appreciate hearing them.
  2. Are you certain you haven't gotten any intensification? I have always used selenium diluted 1+2 with distilled water (in fact, I've been using the same bottle of this solution for many years--I don't intensify many negs) and I have always gotten excellent results. It increases the grainyness of the negs, but this is not a problem with large format. I wonder if the stain on the pyro negs is masking the intensification effect? Have you actually measured them before and after with a densitometer?
  3. Hi Joe,

    Sounds like your neg is thin/weak. Although I have no experience with your film, I do have experience with thin negs. LOTS OF THIN NEGS. My learning curve has been long and steep.

    You're developing a latent sliver image. Exposure yields density - development yields contrast. Sounds like you had neither. My thought is because the image is weak there is not enough developed silver image for the Selenium to "hang on to". So it had no visable effect. Have you tried chromium intensifier? Also contraction development (N-1, N-2) requires additional exposure to hold the shadows (down rating the film speed).

    If I'm wrong on any count I'm sure someone will correct me - - - and often.

    Good luck.
  4. Joe,
    Use VMI intensifier. The formula is listed in Anchell's darkroom cookbook, the original one, not the film developing cookbook. It is a mercury intensifier and as such is toxic. I have used it on PMK negatives and you can really see the intensification. It leaves a orange color on the negative. It can be a little tricky to use and sometimes it comes out uneven, but you can just remove it by immersing the negative in fixer and rewashing. Refer to Anchell's first book for more information about this intesifier.Victor's Mecury Intensifier (VMI)
    You will have to find a chemical company that will ship the (I believe) mercuric chloride and this can be expensive. But it does work well.
    Art Nichols
  5. Sorry, that should read, "latent silver".

    My typing has a learning curve also.
  6. Assuming you don't have the problem of thin negatives, I agree with the above that general stain, maybe excessive general stain, of your pyro negatives is masking the effect of the intensification, maybe even inhibiting the intensification (that latter is just a notion of mine, no science). I'm not sure I see the point of putting a densitometer on your negatives, however, because densitometers don't read pyro negatives correctly (well, maybe the blue channel of color densitometers, sort of). Anyhow, you may have a good reason here (as if you needed another one) of controlling general stain better: (1) Eliminate the developer after-bath recommended by Hutchings and others. (2) Ditch PMK and try the WD2D pyro formula (the "Wimberly" formula). It's a cleaner developer. Less general stain. It's set forth and discussed in the back of the Hutchings book. -jb
  7. Your main problem was the under development. Why did you under develope if intensification was what you wanted? Why didn't you just develope normally in the first place? By under developing you didn't activate enough silver molecules for the selenium to change to silver selenide. And you didn't mention the second development portion normally done with pmk pyro schemes. And did you use the recommended alkaline fixer?
  8. Stain will not inhibit intensification by selenium, as it is emulsion silver that is being converted to silver selenide, not the stain. That is why a densitometer should be of use--to read the density of the silver prior to, as well as after, intensification.

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