How to cyanotype

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Last updated: April 4, 2026

Quick Answer: Cyanotype is a photographic printing process that produces a cyan-blue print. To create a cyanotype, you coat a surface (like paper or fabric) with a solution of ferric ammonium citrate and potassium ferricyanide, expose it to UV light (sunlight is common), and then rinse with water to reveal the characteristic blue image. The process is relatively simple and can be done at home with basic materials.

Key Facts

The cyanotype process was invented in 1842 by Sir John Herschel.
It's one of the oldest photographic printing methods.
The process uses UV light to create the image.
The final print is a distinct Prussian blue color.
Cyanotypes can be made on various surfaces including paper, fabric, and wood.

What is Cyanotype?

Cyanotype is a historical photographic printing process that produces a distinctive cyan-blue print. Invented by the English scientist Sir John Herschel in 1842, it is one of the earliest methods of creating a photographic image without a camera. The process relies on the photosensitivity of iron salts. When exposed to ultraviolet (UV) light, these salts undergo a chemical reaction, forming Prussian blue, which is the characteristic pigment of a cyanotype.

How Does Cyanotype Work?

The cyanotype process involves coating a substrate, typically paper or fabric, with a mixture of two light-sensitive chemicals: ferric ammonium citrate and potassium ferricyanide. These chemicals are usually mixed separately and then combined just before use, or purchased as a pre-mixed solution. The substrate is then coated evenly and allowed to dry in a dark place, as ambient light can prematurely expose the chemicals.

Once the surface is dry and ready, objects are placed on top of it. These can be natural objects like leaves, flowers, or feathers, or man-made objects such as stencils, lace, or even photographic negatives. The coated material is then exposed to UV light. Sunlight is the most common and accessible source of UV light for cyanotype printing. The intensity of the sunlight and the duration of exposure will affect the final print. Areas of the substrate that are exposed to UV light undergo a chemical change, converting the iron compounds into Prussian blue.

After sufficient exposure, the object(s) are removed, and the print is rinsed with water. The water washes away the unexposed, water-soluble chemicals, leaving behind the insoluble Prussian blue pigment in the areas that were exposed to UV light. This creates a silhouette or a tonal image of the object placed on the surface. The intensity of the blue can be further intensified by soaking the print in a weak solution of potassium ferricyanide or by oxidizing it with hydrogen peroxide, though these steps are optional and can alter the final appearance.

Materials Needed for Cyanotype

To get started with cyanotype printing, you will need:

Cyanotype chemicals: Ferric ammonium citrate and potassium ferricyanide. These can often be purchased as a kit or separately.
Coating materials: A brush (foam or natural bristle), roller, or sponge for applying the chemicals evenly.
Substrate: High-quality paper (watercolor paper is ideal), cotton fabric, or other absorbent materials.
Objects for printing: Leaves, flowers, lace, negatives, stencils, etc.
UV light source: Sunlight is the most common, but a UV lamp can also be used.
Water: For rinsing the print.
A dark space: To mix and apply chemicals and to dry the coated substrate.
Optional: Gloves, trays for rinsing, a squeegee for even coating.

Step-by-Step Cyanotype Process

Prepare the Surface: Ensure your paper or fabric is clean and dry.
Mix the Chemicals: If using separate solutions, mix equal parts of ferric ammonium citrate and potassium ferricyanide in separate containers. Do this in low light conditions.
Coat the Surface: Using a brush or roller, apply a thin, even layer of the mixed chemicals to your chosen substrate. Avoid brush strokes if possible.
Dry the Coated Surface: Allow the coated surface to dry completely in a dark room or under indirect light.
Arrange Objects: Place your chosen objects or negatives onto the dried, sensitized surface.
Expose to UV Light: Place the setup in direct sunlight or under a UV lamp. Exposure times can vary from a few minutes to an hour or more, depending on the light intensity and the desired effect. Observe the print; the sensitized areas will often turn a pale greenish-yellow as they are exposed.
Develop the Print: Once exposed, remove the objects and rinse the print under cool running water. Continue rinsing until the unexposed chemicals are washed away and the blue image is fully developed.
Fix and Dry: The print is now a cyanotype. You can optionally "fix" it by soaking it in a dilute solution of hydrogen peroxide or citric acid to deepen the blue, but this is not always necessary. Allow the print to air dry completely.

Tips for Better Cyanotypes

Use quality materials: Heavyweight, acid-free paper or tightly woven cotton fabric works best.
Even coating is key: Apply the sensitizer in thin, even layers to avoid blotchiness.
Experiment with exposure: Different light conditions and exposure times yield different results.
Test strips: Make test strips to determine optimal exposure times for your conditions.
Post-processing: Explore toning with tea or coffee, or intensifying with hydrogen peroxide to achieve various shades of blue and brown.
Safety: While generally safe, it's good practice to wear gloves when handling the chemicals and work in a well-ventilated area.

Cyanotype printing offers a wonderfully accessible entry into alternative photographic processes, allowing artists and hobbyists alike to create beautiful, unique blue prints with a touch of historical charm.