KRST neg test...is this what it should look like?

Discussion in 'B&W: Film, Paper, Chemistry' started by curiousart, Jul 31, 2017.

  1. curiousart

    curiousart Subscriber

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    Hi Folks,

    I've begun testing for residual hypo and silver after processing my negatives. Only, I'm not exactly sure if what I have here is normal when straight selenium toner is applied to a dry negative, or if the test shows I'm fixing insufficiently.

    Arista Edu 100, processed 10 min in D76 1:1, fix 1 and fix 2 in Superfix, 30 seconds each w/ constant agitation (clip test clear time was about 12 seconds), Ilford wash and dump method. Straight selenium was applied to the emulsion side for approx. 3 minutes.

    The sub par scan makes the spots look darker than they really are, so I included a sub par cellphone shot. In krst2.jpg, you can see that the spot is a light, transparent brown, not what I'd describe as being a stain.

    Thanks,
    Art
     

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    curiousart

    curiousart Subscriber

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    ...I might be answering my own question here, but isn't what I'm really supposed to be looking at is the wet blob of selenium toner, and not the toned film? Duh. The blobs were clear.
     
  3. Rudeofus

    Rudeofus Subscriber

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    Selenium toner reacts with both silver halide and metallic silver, darkening both. If you have some silver density already (e.g. developer fog), this image/fog silver will darken in selenium toner and give you the impression of incomplete fixing. Try to fix&wash with your standard procedure applied to an unexposed and undeveloped test clip, and repeat this selenium toner droplet test.
     
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    curiousart

    curiousart Subscriber

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    Thanks, Rudeofus...I'll do that and post the results. Maybe I should do the same with the residual hypo test?
     
  5. Doremus Scudder

    Doremus Scudder Member

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    It's fairly easy to establish a benchmark. Just overfix and overwash by a large margin, so you are really sure that fixation and washing are way more than adequate, and test these negatives. Use an unexposed but normally developed and stopped strip of film for this. Keep it for future reference.

    Best,

    Doremus
     
  6. Rudeofus

    Rudeofus Subscriber

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    Residual Hypo Test should not be directly affected by image silver, but it may be easier to judge the results with a fully transparent test clip ...
     
  7. Gerald C Koch

    Gerald C Koch Subscriber

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    I believe that Kodak recommends diluting KRST 1+9 for the test. Apply a single drop to the blank leader which has been squeegeed and after 3 minute blot dry. You should only the barest darkening.
     
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    curiousart

    curiousart Subscriber

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    Interesting. This film is the last roll of some home rolled Arista I've been sitting on for quite some time, which might explain the fog. I don't think the Arista is ever clear, either--it has a blue tint. I'm going to try my tests on some fresh HP5 and see what happens.

    The hypo test left no discernable mark.

    As far as the 1+9, I believe you're right, Gerald. Someone had posted something about using it straight, but that may have been for prints. I'll try it 1+9.

    Thanks for all the advice--it's going to be great to have a handle on the technical stuff. I'll give this all a shot in a day or two.

    Art
     
  9. Doremus Scudder

    Doremus Scudder Member

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    Kodak does indeed recommend a 1+9 dilution for KRST as a residual silver test. Using it straight is a viable option and maybe easier for some. There was a post here somewhere sometime ago about just this. I can't seem to find it easily at the moment, but the gist was that straight KRST worked as well or maybe was a tiny bit more sensitive compared to the 1+9 dilution. Prints or film, it shouldn't matter.

    Best,

    Doremus
     
  10. Gerald C Koch

    Gerald C Koch Subscriber

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    To pass the test the spot should be a barely perceptible discoloration. On prints where there is a white background the spot would appear beige again barely perceptible.
     
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    curiousart

    curiousart Subscriber

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    Hi Folks,

    I'm happy to report that while the rest of my technique may be pretty suspect, my washing and fixing is major league pro-level stuff. I clipped a bit of unexposed film from the tail of a roll of HP5 I shot, fixed with two fixes, did the Ilford fill-and-dump. Applied selenium 1:9, no discoloration. Dunked the clip in residual hypo test, and it came back absolutely clear. I'll be doing this on a regular basis. I greatly appreciate everyone's guidence, thanks everybody! It's a relief to have a grip on at least this part of my technique...