Exploration of iron based photography

The cyanotype is a photographic process developed in the 1840s by John Herschel which typically relies on the photosensitivity of ferric ammonium citrate or ferric ammonium oxalate in conjunction with potassium ferricyanide to create an image made of the pigment prussian blue.

Chemically it represent the photoreduction of an iron(III) di- or tricarboxylic acid salt and subsequent reaction with the ferricyanide or ferrocyanide ion to form ferric ferrocyanide also known as prussian blue.

In it’s classic and most well known form it is usually used for making contact prints either for artistic or technical purposes.

I have spent the last few years investigating improvements to this process to make it suitable both for use with enlargers and in camera photography.

The goal of my current research is further increase of sensitivity by investigating alternative iron salts and a process of dye sensitization to achieve a broader spectral response, and a method of manufacturing plates and film using a gelatin free process based on agar.

  1. In camera cyanotype negative on glass
    In camera cyanotype negative on glass
  2. Berliner Dom, toned cyanotype made from 35mm negative
    Berliner Dom, toned cyanotype made from 35mm negative
  3. Cyanotype print of 35mm photo of an orchid
    Cyanotype print of 35mm photo of an orchid
  4. High power DIY enlarger head for cyanotype printing
    High power DIY enlarger head for cyanotype printing
  5. Cyanotype printing setup
    Cyanotype printing setup
  6. Cyanotype printing
    Cyanotype printing


Related blog posts

The great cyanotype comparison

Friday December 30 2022, 1399 words — A comparison of a multitude of cyanotype processes and their suitability for enlarger based printing
Filed under: Cyanotype, Photography

This post was originally posted to my tumblr in 2017, this version has been slightly revised.

While trying to improve the quality of the cyanotype prints made on my home built enlarger I came across a whole number of different techniques for increasing the sensitivity and quality of cyanotype prints, but I’ve never done a comprehensive comparison.

So a few days ago I sat down and tested 6 different cyanotype formulas and techniques. All prints were made on A5 size printer paper and were exposed for 15 minutes. I chose a negative that has a wide dynamic range with deep shadows and some very bright highlights. All images were first washed in tap water and then in a weak solution of acetic acid and hydrogen peroxide.

I also tested toning with three of the techniques using a mix of tannic acid and black tea.

Most of the different formulations used here were taken from Mike Ware’s excellent Cyanomicon which can be found here:

Lets begin.

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