First Cyanotypes were only a partial success. The first problem is understanding the sensitivity of the emulsion to light. I used a standard commercial product which advised 10 to 15 minutes exposure. I had no idea how old the emulsion is – would that effect the exposure? UV light is needed for the photochemical reaction, so only sunlight would do, on a rainy North UK day in winter – how long exposure would be needed – surely much longer? A test strip ‘developed’ in water showed quite literally blank after 15 minutes, so I guessed an hour might do it, got distracted and failed to spot the rain shower. The results? Areas that came out seemed to be ‘over exposed’ – very contrasty, and places with subtle darks went solid prussian blue. One experiment failed as rain water seeped under the glass frame being used and the plastic printed negative leached black soluble ink. The result is actually quite atmospheric and the negative is enticingly damaged…..
ensure a sunny day! or at least a rain free one!
Consider a UV lamp? more control possible but lacks the nostalgia(maybe a good thing)….