Cyanotype – Basic techniques


tulips 3in 300The cyanotype, or blueprint, process dates back to 1841 when it was discovered by Sir John Herschel. Although cyanotypes were originally produced on paper they work very well on many surfaces such as wood, the rough side of leather, unglazed ceramic and, most importantly to me, on natural fibre fabrics.

poppiesCyanotypes are contact prints so the image is the same size as the object or negative used to create it. These beautiful white images on a Prussian blue background can range from delicate and subtle to sharp and angular.

The basic process involves four main stages and requires no darkroom, no enlarger and no precise developing procedures. That’s my kind of process!

Before you start doing anything with cyanotypes read the Health and Safety guidelines for some advice on how to work safely with these common chemicals. The names might be scary but the chemicals aren’t, as long as you apply some common sense and good work practices.

Okay, enough waffle, on to the good bits!

 1.  Firstly you make a yellow/green light sensitive solution. I use the recipe from Barbara Hewitt’s book ‘Blueprints on Fabric’ (details on the book list under Odds and Ends) which is about 30g (1oz) of ferric ammonium citrate plus about 15g (1/2oz) of potassium ferricyanide (nothing like as nasty as the name might suggest!) stirred into 250ml (8fl oz) warm water. The exact quantities aren’t critical, you just want a ratio of about 2:1 by weight. The resulting solution is light sensitive and should be stored in a well labelled bottle, in a cool, dark place. This solution is applied to the surface and is left to dry somewhere dark. This amount of solution should treat something like a metre of medium weight cotton but it does vary considerably with the type, weight and weave of the fabric.
ready-for-exposure-2502.  Then you place objects, flowers, foliage or a photographic negative on top of the treated fabric, sometimes pinning it into position or placing a sheet of glass on top to get a close contact.
exposed-2503.  The whole thing is exposed to the sun or another form of UV light. You can expose a cyanotype simply by laying it in the sun but since I live in the UK I often have to use a UV lamp or sunbed! Whatever your source of UV light you’ll get the sharpest results by having the light source at right angles to the fabric. You may have to tilt the board to get the best angle. When the iron salts in the light sensitive solution are exposed to UV light a chemical reaction takes place and they are reduced to their ferrous state. You can judge when the exposure is ‘cooked’ by the colours changing: exposed areas (that will be blue in the finished image) turn dark blue and then slate grey/charcoal colour. The highlights (unexposed areas that will be white in the image) should still be the original yellowy/green and the midtones should be dark blue.This process can take anything from a few minutes in hot, summer sunshine at midday, to 40 minutes or more under a sunbed or a couple of hours in winter sun.
end-result-2504.  Once the exposure is complete the print is washed in plain water. The light sensitive solution that has been covered up simply washes away in the rinsing process leaving a white image. The exposed background oxidises and turns a gorgeous Prussian blue. This oxidation takes something like 24 hours so don’t be worried if your blue is a bit pale initially.

If you think you might like to try this lovely process and learn about the different methods of applying the solution, how to create your own digital negatives and how to colour your cyanotypes etc you might be interested in my first book, ‘Cyanotypes on Fabric’ – this is currently out of print but I’m hoping to re-issue it later this year. There is a selection of books on cyanotyping on the books page of the Odds and Ends section of this web site.

There is a pdf version of this page which you can download – cyanotype basic techniques.