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Thread: Trying out Chromium intensifier

  1. #1

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    Trying out Chromium intensifier

    Trying out intensification myself in this video

    Intensification is the process to increase contrast or density of a film or print through the use of chemicals. In this video I explored how can I mix my own chromium using a floor cleaner as a source of diluted hydrochloric acid. I also tried to intensify both photo paper and prints.
    Watch to the end to see the results!




    or a digital converted photo of the original negative vs the intensified negative
    Click image for larger version. 

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  2. #2
    Tin Can's Avatar
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    Re: Trying out Chromium intensifier

    Thank you.

    I will need this technique soon!
    Tin Can

  3. #3
    Drew Wiley
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    Re: Trying out Chromium intensifier

    Just be aware that ordinary pool supply or hardware store muriatic acid is still plenty strong enough (around 18% hydrochloric solution) to destroy your lungs if you spill it in an unventilated space. I know a number of people whose health was destroyed for life, and lungs permanently scarred, by using off-the-shelf floor etches carelessly. Either dilute it further down outdoors or use a fume hood.

  4. #4

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    Re: Trying out Chromium intensifier

    When I was young chromium intensifier was common. As soon as I knew enough about chemistry to realize it's dangers, I stopped using it. There are other safer methods which also do not amplify grain.

  5. #5

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    Re: Trying out Chromium intensifier

    Chromium intensifier allowed me to save a number of negatives obtained many hours of air travel from home (too short dev time indicated by Fuji for D-76 1+1). Selenium toner was not effective enough, by far. Two things I learned while making systematic tests before treating the precious negatives:
    • Hydrochloric acid from the hardware store was not just good enough, probably some impurity interfering with the intended re-halogenation?
    • Yellow stain seems to never completely clear by just water washing (between bleach and re-dev). Found the trick in an old Kodak/UK brochure.
      Wash thoroughly; then clear in 5% sodium carbonate; rinse; proceeed to re-develop.
      This also helped maintain uniform intensification from low (shadows) to high (highlights) densities. Without the clearing step, the intensified negative had a compensating HD curve.

    Hope this helps.

  6. #6

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    Re: Trying out Chromium intensifier

    Something else. The +6 chromium ion is nasty stuff.
    - Beware of dust when mixing (mask)
    - Wear gloves when using solution
    - Reduce the Cr+6 ions before dumping. Figure out the mass of dichromate in the solution you want to dump. Dissolve twice that amount of sodium sulfite (includes some margin). The solution turns green as Cr+6 is reduced to Cr+3, while sulfite is oxidized to sulfate.

  7. #7
    Tin Can's Avatar
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    Re: Trying out Chromium intensifier

    Good advice
    Tin Can

  8. #8

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    Re: Trying out Chromium intensifier

    A somewhat safer intensification process: a standard rehal bleach of ferricyanide and potassium bromide, followed by redevelopment in a staining developer. This can be repeated any number of times; density and contrast will keep incresing with each cycle.

  9. #9

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    Re: Trying out Chromium intensifier

    Quote Originally Posted by revdoc View Post
    A somewhat safer intensification process: a standard rehal bleach of ferricyanide and potassium bromide, followed by redevelopment in a staining developer. This can be repeated any number of times; density and contrast will keep incresing with each cycle.
    Pyro has it's own problems, but yes it is somewhat safer. Potassium Dichromate is listed as a "4" on the NFPA 704 Fire diamond scale for Health. Meaning "Very short exposure could cause death or major residual injury". Catechol is a 3 meaning "Short exposure could cause serious temporary or moderate residual injury", somewhat comforting I guess?

  10. #10

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    Re: Trying out Chromium intensifier

    In my experience there's a limit to the repeated build up of contrast both with chromium intensifier and especially with staining redevelopment. After a few (ca 3) rounds no significant additional density was deposited when I tried it, with chromium intensifier very convincingly being more capable of adding density than staining developers, at least when non-UV printing processes are consequently used.

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