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What went wrong?

My RA-4 colour prints have a colour cast, or the colour changes from print to print

Darkroom prints

What you're seeing

The whole print is tinted (too magenta, too cyan, too yellow and so on), or neutral greys change colour between prints made with the same settings.

Check this first

Check this first

Judge the dry print under light like the light it will be shown in, about 5000 K. Correct density first, then colour.

Likely causes, most common first

  1. 01

    Filter pack needs adjusting

    Common
    How to tell
    The same cast on every print from the negative, even across sessions.
    Test it
    Make a series of prints changing one filter at a time, keeping notes. Use Kodak's table: for a cyan print subtract magenta and yellow (or add cyan); magenta, subtract cyan and yellow (or add magenta); yellow, subtract magenta and cyan (or add yellow); red, subtract cyan (or add magenta and yellow); green, subtract magenta (or add cyan and yellow); blue, subtract yellow (or add cyan and magenta).
    The fix
    Start from the paper maker's suggested pack (Kodak gives 40M + 50Y for Endura Premier). With dichroic heads Kodak's rule of thumb is to change exposure about 1% per unit of magenta change; yellow changes usually don't affect density.

    Sources Eastman Kodak Company, KODAK PROFESSIONAL PORTRA III Paper Technical Data; Kodak Alaris, KODAK PROFESSIONAL ENDURA Premier Paper Technical Data (Dec 2017)

  2. 02

    Judging under the wrong light

    Common
    How to tell
    The print looks fine in one room and wrong in another.
    Test it
    Look at the print under a lamp of about 5000 K with a high colour rendering index and at least 538 lux, as Kodak recommends.
    The fix
    Always judge test prints under the same viewing light.

    Source Eastman Kodak Company, KODAK PROFESSIONAL PORTRA III Paper Technical Data

  3. 03

    Developer temperature or time drifting

    Common
    How to tell
    Same exposure and filtration give different colour or density from run to run, often drifting through a session.
    Test it
    Check the developer temperature before each run and process two identical exposures back to back. Kodak asks for the developer to stay within ±0.3°C of the chosen temperature.
    The fix
    Use a water bath and an accurate thermometer, keep the same time every run, and lengthen the bleach-fix by the same amount if you lengthen development.

    Source Kodak Alaris, Tray, Drum, and Rotary-Tube Processing with KODAK EKTACOLOR RA Chemicals

  4. 04

    Developer contaminated with bleach-fix

    Occasional
    How to tell
    Problems start after a spill or after reusing a jug. Kodak says even minute amounts of bleach-fix severely contaminate the developer.
    Test it
    Mix fresh developer in a separate, clean container and repeat a known print.
    The fix
    Keep a separate mixing container for developer and rinse drums and tubes thoroughly between runs.

    Source Kodak Alaris, Tray, Drum, and Rotary-Tube Processing with KODAK EKTACOLOR RA Chemicals

  5. 05

    Stray light or a safelight fogging the paper

    Occasional
    How to tell
    Borders are not clean white and a colour veil covers the image. Kodak says to handle RA-4 paper in total darkness and to eliminate stray light from enlarger heads, timers and LEDs.
    Test it
    Process an unexposed sheet handled in total darkness and another handled as you normally do. If the second is tinted, light is reaching the paper.
    The fix
    Work in total darkness. If a safelight is unavoidable, Kodak allows a KODAK 13 amber filter with a 7.5 W bulb at least 1.2 m away, but warns it will affect results.

    Sources Eastman Kodak Company, KODAK PROFESSIONAL PORTRA III Paper Technical Data; Kodak Alaris, Tray, Drum, and Rotary-Tube Processing with KODAK EKTACOLOR RA Chemicals; Eastman Kodak Company, How Safe Is Your Safelight? A Guide to Darkroom Illumination

  6. 06

    Paper stored warm or damp

    Occasional
    How to tell
    Odd results with one older or badly stored box. Kodak says high temperature or humidity may cause unwanted print quality changes.
    Test it
    Print the same negative on a sheet from a fresh box with the same settings.
    The fix
    Kodak: store unprocessed Endura paper between 4 and 24°C in the sealed package, and let refrigerated paper warm up before opening.

    Sources Kodak Alaris, KODAK PROFESSIONAL ENDURA Premier Paper Technical Data (Dec 2017); Eastman Kodak Company, KODAK PROFESSIONAL PORTRA III Paper Technical Data

Avoiding it next time

  • Keep a notebook of filter packs and exposure for each negative.
  • Hold developer temperature steady with a water bath.
  • Mix developer in its own container.

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