How to Use Cyanotype Paper | Sun Prints Made Simple

For the full breakdown, see our best Cyanotype Paper guide.

Making your first sun print takes about fifteen minutes of hands-on time, and the process rewards patience over skill. The paper comes pre-sensitized, so the chemistries are already coated and dry. Your job is simple: keep it dark until ready, arrange a subject, let UV do its work, and wash away the unexposed chemicals to reveal the classic Prussian blue image. This guide walks through the full process from unboxing to a finished, dried print — with the common pitfalls named so you can avoid starting over.

What Is Cyanotype Paper and How Does It Work?

Cyanotype is a 19th-century photographic printing process that relies on two iron-based chemicals — typically potassium ferricyanide and ferric ammonium citrate — coated onto paper. When UV light hits the coating, a chemical reaction turns the exposed areas blue. The parts covered by your objects or negative stay unreacted and wash away in water.

One commercial kit’s instruction sheet notes the sensitizer can be used on paper, fabric, wood, leather, and canvas, so the craft extends beyond blue sheets. Unlike a camera, it is a contact-printing method: the subject must sit directly on the paper at full size. The two common product forms are pre-coated paper (ready out of the black bag) and liquid sensitizer kits you brush onto your own surfaces. This guide covers the pre-coated workflow, with notes on the liquid route where relevant.

Step-by-Step: Making a Cyanotype Print

The core method is simple: expose, rinse, dry. Each step has a correct way to avoid ruined paper.

1. Set up in subdued light. Work in a dim room or shade, away from windows.
2. Remove one sheet only. Open the black bag, take out a single sheet, and immediately reseal. The Liverpool Museums’ cyanotype guide for beginners stresses keeping remaining sheets in the dark until needed.
3. Place the paper on a rigid surface. Cardboard or a clipboard gives a flat, stable base for good contact.
4. Arrange your subject. Pressed leaves, flowers, feathers, lace, keys, or a full-sized negative all work. Lay them directly on the paper. For flat botanicals and negatives, place clean glass or plexiglass on top to hold everything flush and sharpen detail.
5. Expose in sunlight. Carry the board outside and lay it flat in direct sun. Leave it until the paper shifts to a pale, bronzed, faded look. The Denver Art Museum’s process guide notes exposure typically runs 5–20 minutes depending on sun brightness;
6. Rinse in water. Bring the board indoors and remove the subject. Run the paper under cool running water, or immerse it in a tray, until the wash runs clear and the yellow-green stain washes away. Plan for at least 5 minutes; a full 10 is safer for a stable image.
7. Dry flat. Lay the wet print on a flat surface or hang to dry. The blue deepens as it dries.

One instruction sheet notes an optional final step: after washing, a short dip in a very dilute hydrogen peroxide bath instantly deepens the blue. It is purely cosmetic and skippable.

Common Mistakes That Ruin a Good Print

Most failed cyanotypes trace back to one of four errors. Knowing them in advance saves paper.

• Fogging the paper. Handling sheets in bright indoor light or leaving the bag open lightly exposes the paper, producing a washed-out background. Work dim; reseal the bag immediately.
• Underexposure. Weak, pale prints almost always mean the exposure ended too early. The general rule from the Science and Media Museum’s introduction to cyanotype is that overexposure is safer than underexposure — too long just deepens the blue, too short gives a faint ghost of an image.
• Poor contact. A leaf that curls or a negative that lifts leaves fuzzy, blurred edges.
• Short washing. Insufficient rinsing leaves a yellow-green residue that fades or stains over time. Keep rinsing until the water runs completely clear.

If you coat your own paper from a liquid sensitizer kit, two extra rules matter. The Liverpool Museums booklet says to apply a thin, even coat with the provided hake brush, let it dry in the dark, and allow a full 24 hours before use.

FAQs

Can I use cyanotype paper indoors?

Yes, but only with a UV light source. A UV lamp works for exposure, and indoor fluorescent or LED lighting is generally safe for setup so long as you work in subdued light and avoid direct sun through windows. Test exposure time with a small test strip — indoor UV exposure varies significantly by lamp strength and distance.

Why did my print come out too light?

The most common cause is underexposure. The paper needs enough UV to fully react; if the exposure is too short, the image washes out. Try extending exposure time — the paper can handle it — and ensure your subject lies flat against the glass for maximum contact. Bright midday sun is the most reliable light source.

What materials work best for sun prints?

Flat, opaque objects produce the sharpest silhouettes — pressed leaves, ferns, feathers, keys, lace, and photographic negatives all work well. Avoid thick or curved objects that won’t lie flat. For botanical subjects, press flowers and leaves in a book for a few days first so they make full contact with the paper.