How the Cyanotype Process Works
Cyanotype uses two iron salts: ferric ammonium citrate and potassium ferricyanide. Mixed together and coated on paper or fabric, they form a light-sensitive layer. UV light (sunlight or a UV lamp) reduces ferric iron to ferrous iron, which reacts with ferricyanide to form Prussian blue, an insoluble pigment locked into the fiber. Unexposed areas wash away with plain water, leaving the characteristic deep blue print. The process requires no darkroom, no enlarger, and no stop bath. It is one of the oldest photographic processes and still one of the most accessible.
2to 5 Minutes
1to 1 Ratio
Mix and Coat in Subdued Light
Mix equal parts solution A (25 g ferric ammonium citrate per 100 ml water) and
Mix and Coat in Subdued Light
Mix equal parts solution A (25 g ferric ammonium citrate per 100 ml water) and solution B (10 g potassium ferricyanide per 100 ml water) just before use. Working in shade or dim indoor light, apply a thin even coat to watercolor paper (140 lb or heavier)
Arrange Objects or Negatives and Expose
Lay your dried coated paper on a hard board.
Arrange Objects or Negatives and Expose
Lay your dried coated paper on a hard board. Place flat objects (leaves, feathers, lace, keys) or a printed transparency negative directly on the surface. Cover with a sheet of glass to hold everything flat and ensure sharp edges. Take outside into
Wash and Oxidize the Print
Remove objects in shade and immediately immerse the print face-down in a tray
Wash and Oxidize the Print
Remove objects in shade and immediately immerse the print face-down in a tray of cool water. The unexposed yellow-green coating washes away within 1 to 2 minutes, leaving clear paper where it was protected and blue where it was exposed. The image will
Factors That Shift Exposure Time High UV index, reflective surfaces nearby, and thin paper all speed up exposure. Overcoated paper, cloudy skies, and thick objects reduce effective UV. Keep a test strip log: cut a strip of coated paper and expose it alongside your main print, covering it in sections at 1-minute intervals. This gives you a reliable reference for future sessions in the same conditions. Cyanotype on fabric (cotton or linen) requires longer exposure than paper and benefits from a so