What is cyanotype and how to start taking photos in Prussian Blue

In this article I will explain cyanotype for people who are approaching this photographic and artistic technique for the first time.

On a trip I made this summer to Tabarca Island, there was a local art store that worked a lot with cyanotype prints, it is called Tabarca Blue, its owner was explaining to us how it works and what it consists of and it seems to me a simple technique to do at home.

Here are 2 works that they gave me. One made with a seagull feather found on the beach (single print) and the other from an x-ray of Eugerres plumieri.

The Prussian Blue obtained with these photographs is beautiful.

What is it

Cyanotype is a photographic technique or process that produces cyanotypes that are negative copies in this characteristic blue tone, which is called Prussian blue or blueprint in English.

Cyanotype is a photographic printing process that uses ultraviolet light for development.

Invented in 1842 by the scientist and astronomer Sir John Hersche.

In 1943, the botanist and photographer Anna Atkins published a book of algae cyanotypes, giving the technique a photographic use and also using it as a scientific tool. A link to part of her work.

In addition, you can also see a digital collection of Anna Atkins’ cyanotypes (photographs) at The New York Public Library Collections

How to do it

I’ll leave the procedure I’m going to follow for my first impression. From here I’ll do some tests and tell you my method.

To start, instead of buying the elements for the solutions, I’m going to buy a more commercial solution, since the idea is to do it quickly with the girls. Specifically, I’m going to use this Jacquard cyanotype kit.

It can be done at home. They sell kits with the necessary ingredients. But if you want it to be cheaper, you can buy them separately and in larger quantities.

Step by step

If you decide to make the mixture yourself, you need the following ingredients

Ingredients

ferric ammonium citrate
potassium ferricyanide

Mixture of elements

First, measure 25 g of ferric ammonium citrate and add water to make 100 ml. Next, measure 10 g of potassium ferricyanide and mix it with water to make 100 ml. Make sure that both chemicals are completely dissolved. Finally, mix the two solutions under a dim light. It is now ready to be coated on the paper.

Paint the paper

The solution must be spread well on watercolour paper of at least 240 gr so that it holds up well.

Use metal-free brushes because they can react and spoil the solution

Do this process in a place where there is no direct light or bulbs that emit ultraviolet light

Once painted, let it dry in a dark and dry place.

Preparing the negative

Take our negative and put it on our already dry paper. It helps to use a glass to keep the negative fixed and the paper straight.

If the negative moves in relation to the paper, the photo could be blurry

Exposure

Now there has to be light, we have 2 options: put it in the sun or use an ultraviolet light bulb

With the sun we have less control, in full sunlight we have to leave it for about 20 – 30 minutes, but it will depend on our area and the day. Since the radiation varies a lot. If we leave it for less time, it will be a very faint blue that will fade over time. And what we are looking for in these photographs is a very intense blue, Prussian Blue

A visual reference to know when it is ready is that the emulsion we have applied has a silver-grey colour. At that moment, we must remove the negative and take it to a place without sun for development.

With an ultraviolet lamp we can control the exact time, since the radiation will be constant.

Development

It consists of washing with cold water. We put the negatives in a bucket for about 5 minutes and do this 3 times.

Finally, let it dry and it is ready.

Making yellow and sepia tones

Cyanotype in yellow

To change the tone of your blue print to yellow, we will put our photograph with blue print in a solution of 4 litres of water and 2-3 tablespoons of TSP (Sodium triphosphate), a powdered soap found in hardware stores. Some laundry detergents contain phosphates and can be used. We soak it in this solution for 5 minutes. The blue will change to yellow. Then we remove it and rinse it in clean water for 2-3 minutes

Sepia cyanotype print

To give a sepia tone to your yellow print, soak it in black tea (5-6 tea bags per 6 cups of water). The more tea bags, the darker the print will be. Stir the print from time to time and then move your print and rinse it in water briefly.

Interesting tips and tricks

Hydrogen peroxide h2o2 will speed up the oxidation.

With 200 mL of prepared solution you can cover 50 A4 sheets

Videos with the process

2 very interesting video tutorials to follow.

This second one is in English but I recommend you watch it with subtitles.

What cyanotype is