Making Enlarged Negatives

Discussion in 'Black and White' started by curtis_lowe, Sep 24, 2014.

  1. I want to make enlarged negatives for some alternative processes like cyanotype etc. and recently got some 8x10 Arista Ortho Lith 2.0 Film. I'm unsure which side is the emulsion side as both are shiny. One side is purple while the other side is yellow/brown. Can anyone advise?
  2. The yellow brown side is the emulsion side.
  3. Making enlarged negatives is also on my future experimental to do list. The Arista film is not notched? If not, can you tell by "feel," like with RC paper?
  4. photowaerehouse ultrafine online
    sells a film that apparently yie;ds a negative from a negative with normal ( not reversal) processing. it is so,ewjat pricey.
  5. Thanks Alan, I think I exposed the purple side. Will it make much difference?

    I didn't feel much difference between the sides Stephen but will test again.
  6. Typically film has an emulsion coat on top and an anti-halation coat under the emulsion. Film suffers from halations, a secondary exposure from the rear. Highlights in the scene play on the film as bright spots. Super bright rays will transverse the film. As they travel they tend to reflect back when they encounter a juncture. Since films have multi coats there are multiple opportunities. This reflected light re-exposes and we get halo effect surrounding what should be sharp defined points. These are called halations. The countermeasure is a dye coat. This colors the reflected light to a frequency that the film is less sensitive to. That’s the purple you are seeing.
    Exposure through the backside is possible but it takes lots more light energy to do the trick. Additionally the image that results will be degraded. Better re-expose to the emulsion side. Incidentally, early in photo history, Wilhelm Vogel, German 1834-1898, while professor at Berlin Technical, tried to mitigate halations. He had an experimental emulsion dyed yellow because early films only responded to violet and blue. The yellow dye was to block any violet or blue re-entry exposure. To his surprise, the yellow dye did the trick but now the film was sensitive to green as well as violet and blue. Vogel had discovered what we call sensitizing dye making possible orthochromatic and panchromatic films. Hats off to honor the professor.
  7. Not an answer to the question, but maybe worth a read:
  8. John S, GREAT link! Thanks!
  9. Sorry to bring this up again but having originally exposed the purple side by mistake, I have since tried the yellow/brown side but found it to need more exposure, so I'm wondering if the purple side is actually the emulsion side? The anti halation layer seems to wash off the yellow/brown side.
  10. Hi Curtis:
    If the purple side requires less exposure, it is the emulsion side. In the darkroom, I often had to test by wetting my finger and feeling the tackiness. The emulsion side is more sticky.
    Sorry if I led you astray.
  11. James G. Dainis

    James G. Dainis Moderator

    You can see which is the emulsion side of the developed film by taking a sharp knife and scraping the film. Emulsion (and image) will come off the emulsion side but nothing will come off the back side.

    I would have thought the purple was the back side, too.
  12. No problem Alan, thanks for your help.
  13. As per James suggestion I scraped both sides and the image came off the purple side.

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