Cyanotype Printing

Now that I’ve got my timing right for exposure I managed to get some images exposed – the images are acetates I had printed a while ago for screen-printing so they are inverted the wrong way but they still look good.

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A little bit about the process, two liquids containing chemicals are mixed – Ferric Ammonium Citrate and Potassium Ferricyanide in equal amounts. This is then painted onto your surface, paper or fabric and left to dry in the dark. It can then be exposed to UV light with your image on top.

Cyanotype test strips and Exposure

As you can see the first test strip is way over-exposed as I assumed for some reason that the exposure times were in hours not minutes! Only the final exposure of 30 mins gives a decent result – experiment was carried out on very hot and sunny afternoon in August. Also for this test I didn’t use glass/perspex on top while exposing, only a thin sheet of plastic so the blotches you can see from around 3hrs to finish are probably from UV light leaking under the acetate.

The second test strip gave a much more accurate indication of exposure times – this test strip was exposed on a hot and sunny/slightly cloudy day, early afternoon, in September. I also used a sheet of clear perspex to press down the acetate into contact with the paper which gives a much better result, heavy glass would probably be better again.

For reference the image is of the sea surface/waves – but as this image was initially for a screen-print the image isn’t inverted correctly. Normally the image would be inverted on Photoshop then once exposed would show the original image.