Starting with Duotone

Cyanotype is like a RPG, the more XP you get, the more complex process you will be able to perform. In the Journey of cyanotype, there’s the basic and quite simple blue monochrome, then the toned monochrome, then come the duotone and for very experimented printers, the 3 colors cyanotype. So, even if I’m not a master with monochrome, I get quite consistant result and decided to move to the 3rd level. There’s again a lot to learn on this level, new parameters to take into account and a lot of failure coming up. The first challenge is to get a picture in color. Really, I don’t really have proper color picture. Then you should choose on with not too much red.

Here’s a quick description of the process (the digital processing is done in gimp):

• Choose your image
• flip image horizontaly“
• saturation to 100%
• separate
  • colors-> components -> decompose

tip :
red is cyan
green is magenta
blue is yellow

• adjustment of the cyan (red) => then export to one file
  • color -> brightness and contrast -> brightness to 127
  • color -> exposure -> black to 0.1
  • color -> invert
  • file -> export -> image-cyan.jpg
• then adjust green and yellow before combining and export
  • select the magenta (green)
    • color -> brightness and contrast -> brightness to 127
    • color -> invert
  • select the yellow (blue)
    • color -> brightness and contrast -> brightness to 127
    • color -> invert
  • select both,
    • go to the green one and change mode to addition
    • go to the blue one and change mode to addition
    • file -> export -> image-magenta-yellow.jpg

Now we have two files, we print them on the usual transparency at the size we want to make the print.

Let’s go for the analog part:

• Size the paper in hot water
• First layer with a 10%+10% cyanotype
• Expose double time from what you are used with the monochrome process.
• Develop in tap water for 5 min.
• Oxidize with H2O2
• Then bleach in 1 table spoon of sodium carbonate in 5L of water
  • First dilute in hot water and then add more water to 5L
  • Bleach for 20 min until the blue is gone and only yellow remains.
• Toning with tonic acid (big spoon) in 2L (dilute in hot water and steer for long time.
• Then bleach again for 2 min. (I forgot that step)
• Dry.
• Second layer in 5%+5% (take 5ml of 10%A+5ml 10%B and add 10ml water)
• Cast and dry quickly (There seem to be a reaction between the cyanotype solution and the toner)
• Expose (normal time)
• Develop in tap water
• Oxidize with H2O2 (not mandatory, time will do the job)
• Dry and you’re done.

Here is a first somehow acceptable result.