Have you ever wondered why blue prints are blue? Well, it’s because in the mid-1800’s an astronomer named John Herschel developed a printing process for copying his notes. He discovered that mixing ammonium iron citrate and potassium ferrocyanide created a photosensitive solution that has come to be known as blue ferric ferrocyanide. When this solution is applied to paper and dried in the dark, it can be activated when it’s exposed to UV light. Any portion of the dried solution that is covered from the light will remain white, and when the paper is rinsed in water the blue ferric ferrocyanide will change from green to “Prussian Blue.” This process creates the blueprint effect.
Summer is the perfect season for creating cyanotype prints and nature can provide the most unique objects to use as negatives. If you’d like to give the process a try, you can purchase the chemicals and mix your own blue ferric ferrocyanide or you can purchase pre-treated papers and fabrics. When working with children, adults must supervise the use of chemicals to ensure they are used safely. If you have any safety concerns, you might choose to use pretreated papers. You can purchase these papers HERE.
Check out this youtube video for instructions: