David M. Röhrscheid blog
Making Cyanotypes
Cyanotype is a photographic printing process that was discovered in 1842. The process produces images in a fascinating hue of deep blue. Once one has aquired the basic chemical ingredients and a few simple tools, they are quite easily produced at home, without the need for a proper darkroom.
I really wanted to make my own photographic prints at home. Since my tiny Tokyo apartment does not offer enough space for a darkroom, this seemed like a good way to start.
The process is a so-called ‘contact print’, requiring a negative to be pressed directly onto light sensitive paper. The negative is most easily made with a common inkjet or laser printer, while the light sensitive medium is created by applying a chemical solution to paper. This allows for some creative freedom in the choice of paper and the way the chemical solution is applied, while the negative remains malleable to digital tools.
The basic process
I will first give a small overview of the process so you can decide whether this is something you want to try. A list of the required tools and a more detailed explanation of each step is given below.
The basic process has these 5 steps:
- Make negative
- Prepare sensitive paper
- Expose
- Develop
- Preserve
Negatives are made by printing black ink on a transparency with a regular inkjet or laser printer. Depending on the size of the printer you have at home, this will limit you to prints of the size of paper you can print on.
To sensitize the paper, apply a solution of potassium ferricyanide and ferric ammonium citrate in water using a brush (see below for details). You can use any paper that will hold the color while being strong enough to withstand soaking for half an hour and a thorough wash in running water. I use thick water colour paper from the art store. After applying the solution, leave to paper to dry in a dark spot.
To expose the image, place the negative on top of the sensitized paper and press the two firmly together using a glass plate. After that, simply place the setup in bright sunlight for about 10 minutes. Exposure times will vary with the amount of sunlight you can get, so it is useful to have a test image with a uniform pattern that allows you to expose different parts of the paper for a different amount of time. Using this test image, you can then judge the best exposure time for your image. I have found however, that the sensitivity of the process is in the range of minutes rather than seconds so that you can usually guess the right exposure time after a having aquired some experience.
To develop the picture, simply wash out the unexposed chemical with cold running water. You should wash the image for 10 to 20 minutes and place it in a bath of water for the rest of the unexposed chemical to seep out. At this stage, you can add hydrogen peroxide to slightly darken the blue color of the image. After thoroughly washing the image, leave it to dry for a few hours.
The last step is not necessarily needed and I do not have long-time experience with preserving the cyanotype prints, but I usually spray the image with a water-repellent spray to preserve it.
Tools
These are the tools you need. To produce a negative:
- A printer
- Transparencies that you can print on
To sensitize paper:
- Potassium ferricyanide
- Ferric ammonium citrate
- Water, preferably distilled
- A brush
- A mixing bowl
- A scale
- Water color paper
To expose and develop:
- A glass plate
- A washing bowl or tray that fits your paper
- Hydrogen peroxide (optional). Household bleach is usually just hydrogen peroxide.
- A place in the sun to expose the image
- A place to hang and dry your images
And possibly to preserve:
- Preservant spray from the art store
The steps in detail
Making a negative
The negative is produced by taking a digital picture, turning it into a grayscale picture and subsequently inverting its colors. This can be done with most modern image manipulation programs.
The inverse grayscale picture is then printed onto a transparency. Depending on the type of printer you have, you need a different type. With inkjet printers the transparencies tend to get damaged by contact with water and one should make sure that the sensitized paper is thoroughly dried before bringing the negative and the paper together.
Transparencies are relatively cheap and can be bought at most office supply stores. If you are in Tokyo, simply visit one of the many ヨドバシカメラ stores.
Preparing the paper
This step starts with choosing the right paper. The paper will have a great influence on the appearance and contrast of the final print. It must be strong enough to withstand extensive washing and soaking with water and must not shrivel up when dried.
I prefer 300g/m2 cold pressed water color paper from a local art store (if you are in Tokyo: 世界堂 in 新宿), but you do not necessarily need paper this strong. I usually have some stronger cheap drawing paper around as well. These will change form in the printing process but are strong enough to not tear and are thus well suited for making test prints.
In the next step, a mixture of equal parts (in volume) of a solution of 25g Ferric ammonium citrate in 100ml water and 10g Potassium ferricyanide in 100ml water is applied to the paper with a brush. I have found that making the layer very thin instead of being generous with the solution gives the best results.
Exposure
For the exposure, the negative needs to be pressed firmly against the sensitized paper while exposing the surface to light. This is most easily achieved by placing the paper and negative on a flat surface and putting a glass plate on top. The glass plate is fastened with clamps or rubber bands to keep everything firmly in place.
Development
Developing the image simply consists of washing out the unexposed chemical with water. This has to be done rather thoroughly as it tends to enter the paper quite deeply.
I usually put the exposed paper under running water for a few minutes to wash out most of the chemical from the surface layer. For your first few prints you try to wash out all of the chemical with running water to get a feel for the process and to see how the image changes as the chemical washes out.
After most of the color is washed out, put the image in a tray filled with water to get out the remaining chemical. You should agitate the tray a few time and change the water every so often. I usually leave the prints in the tray for up to thirty minutes.
Before hanging the prints out to dry, you can add a little Hydrogen Peroxide to the tray. This causes the color in the print to darken, giving a deeper color and slightly better contrast in some cases.
