Pelargonium CiliatumBlue is the colour! These botanical blue prints of classic flowers have been inspired by the cyanotype process. This process uses a mixture of iron compounds, which when exposed to UV light and washed in water oxidise to create Prussian Blue images. The technique was invented by John Herschel in 1841 and was made popular by photographer and botanist Anna Atkins. She published Photographs of British Algae: Cyanotype Impressions, in October 1843.