Botanical cyanotypes: from blue to endless possibilities

Botanical cyanotypes are plant prints in shades of deep blue. They are enchanting, opening up an infinite range of possibilities for creating works connected with the plant world and helping us feel closer to nature.

In this article, I share my explorations of botanical cyanotype on different surfaces: paper, wood, stone and fabric. For each one, I offer tips to help you achieve good results with your nature art creations.

I love this artistic technique for its beauty and simplicity, as it allows me to connect with the plants growing near my home. Even children can have fun exploring the plant world by making botanical cyanotypes; it is very educational.

What is botanical cyanotype?

John Frederick William Herschel discovered and experimented with the cyanotype process in the 1840s. Cyanotype is one of the oldest monochrome processes based on the sensitivity of iron salts to light. The paper is coated with a solution of ferric ammonium citrate and potassium ferricyanide using a brush, away from light. The print is made by placing a negative or other objects, such as plants, on the paper. Exposure to natural light takes about 15 minutes, changing the composition of the iron salts. The paper is then rinsed in water to dissolve the unexposed iron salts and left to dry. It is during this drying process that the Prussian blue pigment characteristic of the process forms^[1].

A little later, Anna Atkins, a British botanist with a scientific education from her father, illustrated books on mollusks and created a herbarium using this technique ^[2]. As early as 1843, she used cyanotype to produce photograms of algae in her book Photographs of British Algae. Recognizing the importance of illustrations in botany, she then applied this method to ferns, publishing Cyanotypes of British and Foreign Ferns in 1853. She thus became a pioneer of scientific photography, popularizing this monochrome process ^{[3, 4]}.

Botanical cyanotypes on paper in many forms

For the paper-based process, there are several ways to do it:

1. Conventional cyanotype
2. Wet or experimental cyanotype

Conventional cyanotype involves four steps. First, the iron salt solutions are mixed and the liquid is applied to the paper away from light. The plants are then arranged on the paper and exposed to the sun. UV light reacts with the salts to create blue pigments. In the final step, the paper is washed with water, and the blue develops through oxidation.

Personally, I like using wet cyanotypes to break up the blues and add extra shades and textures. This is the technique I teach in our workshops at Les Pléiades.

What’s wonderful is that cyanotypes can be used to make cards, bookmarks, pictures and even jewellery. To make these bracelets, I used watercolour paper, which I glued onto a bracelet base.

Which products and paper should you use?

You can use various products: I use the Jacquard or Claire Fontaine product kits, but there are others. You can find them in stationers’ and art shops, or online (Amazon, Boesner…); look for a supplier in your area.

For paper, you can use watercolour paper weighing around 300 g, Chinese paper, or even tracing paper with a weight of at least 90 g/m². Here is a video showing how architects’ tracing paper (90 g/m²) can be used to make a lantern, glued onto glass with flour paste and paper made from daylily leaves. The leaves are simply soaked in water, without any chemicals or other materials. This method is called water retting.

Tip for adding nuance to colors

Once the cyanotype had dried, I applied an acrylic varnish to give the colours a slightly greyed look, like faded denim. This will tone down the blue and create shades that go very well with certain clothes. If you want to keep the blues intact, simply varnish your cyanotypes with homemade starch glue made from flour and water.

Botanical cyanotypes on wood

Porous materials make good surfaces for beautiful cyanotypes, and wood works well. However, each type of wood will give a different result.

In this image, I used fir plywood, which is a soft wood, to achieve a more subtle effect, like a background.

Tip for wood

• Using light-coloured wood such as birch, poplar or pine gives better contrast with the Prussian blue of the cyanotype.
• The wood should be untreated and well sanded, ideally with a grit of around 180, to help the solution adhere.
• Treated wood or plywood can be used, but the shades of blue may vary and be less durable.
• Hardwoods hold the solution better on the surface, which encourages the reaction to UV light, but the colour may fade more easily when rinsed. Softwoods absorb more, which can produce softer results. It is therefore recommended that you experiment to achieve the result you want.

Botanical cyanotypes on stone

Stones, shells, and porous ceramics are wonderful surfaces for cyanotypes. However, they must be carefully chosen to ensure the final image is visible and aesthetically pleasing. 

How to proceed with botanical cyanotype on stone?

• It is essential to choose a porous, light-coloured stone, such as a white pebble, a grainy sandstone or any natural, unpolished and untreated stone, for better contrast with the blue. Porosity is crucial, as it allows the light-sensitive solution to be absorbed and adhere well to the surface. To check whether a stone is porous, place a drop of water on it: if it is absorbed, the stone is suitable; if it remains on the surface, the stone is not suitable.
• Wash the stone thoroughly and, if you like, sand it to make it a little smoother.
•  In a room without direct UV light, apply the cyanotype solution twice in succession and, once it is thoroughly dry, arrange the plants on it.
• Use cling film to flatten your plants against the stone.
• Expose it to the sun for at least 1 hour, then rinse.
• Apply an acrylic varnish to protect it. Keep it out of direct sunlight.

In Switzerland, where we live, collecting a few small pebbles is generally not prohibited, except in areas where local regulations apply or where protected areas exist. In France, collecting pebbles from beaches is more strictly regulated and can be prohibited or penalized.

Botanical cyanotypes on fabric: beautiful, but less eco-friendly

Fabric is a wonderful material for botanical cyanotypes. However, I no longer use it, because it requires a lot more solution than other surfaces and is therefore less eco-friendly.

For a single scarf, I had to take 6 litres of waste rinse solution to a hazardous-waste disposal centre—that is enormous! With paper, it would take me more than two years to accumulate that amount for my personal use.

So I have not repeated the experiment on fabric. I will continue making prints on paper, which produce much less waste, while ensuring that I dispose of it properly at a waste disposal centre.

All this offers a vast field for learning and experimentation, allowing me to continually reflect on my interdependence with nature and seek balance within it.

Tips for working on fabric

• It is therefore recommended that you take the first rinse water to a waste disposal centre, with the chemical waste.
• To preserve the intensity of the colours, avoid machine-washing cyanotype-printed fabric or using harsh detergents.
• For best results, use a light-coloured fabric made from natural fibres (cotton, linen or hemp).
• Apply the solution evenly with a wide brush or sponge to the fabric laid flat, ideally on a smooth, non-porous surface such as a wooden board covered with plastic.
• For sharp outlines, choose flat plant material. Press it firmly against the fabric with a sheet of glass or transparent plastic, securing it with clips if necessary. If there is no wind, place a piece of cardboard over it and remove it just before exposing the fabric to the sun.

Here are our upcoming cyanotype workshops at Les Pléiades (Vaud, Switzerland), in an enchanting setting: