An excerpt from Blueprint to cyanotypes: Exploring a historical alternative photographic process. 3 different coating methods for making cyanotypes on fabric, and how to dry and store the coated paper.
The cyanotype process is very “slow” which means the chemicals take a long time to react to light, so you can use dim lighting when you are coating the material. Since drying the material takes considerably longer than coating it, drying should be done in the dark.
Cyanotypes can be printed on any natural paper, cloth or fabric. Cotton, linen or silk are all excellent canvases. The printing will not work on synthetics, like polyester, since the chemicals won’t stick to the fibres in the fabric. A blend of cotton and polyester can work, although the colors may be less vibrant, but the coating method for cyanotypes can make a difference.
Prepare a flat surface for coating with a brush or a rod
Tape some newspaper or manila paper to a flat non-absorbent surface – such as a piece of glass – and tape your paper or material on top of the newspaper.
Then lightly mark the area you want to coat using a pencil and a ruler. Most of the pencil marks will wash away in the final step when you rinse your print.
Three different coating methods for cyanotypes
There are a few different ways to coat your material or paper. Whichever method you choose, remember to stir your chemicals to keep them well blended as you apply them.
The paint method
Using a brush, simply paint the chemicals onto the material. Choose a brush without a metal ferrule, since metal may react with your chemicals. A Japanese hake brush is excellent and will give you a nice even coat. A cheaper bristle household pastry brush, or a foam brush can also work well. Nylon brushes aren’t as effective.
With this method it is best to coat the material several times, in both directions, until it is completely covered. Cover an area slightly bigger than your negative. The solution is yellowish green before processing, so it is quite easily seen if you’ve missed a spot.
You can use the brush strokes around the edges of the print as an effect. Wash your brushes in cold water when you’re finished.
The coating rod method
A coating rod is a very economical way of coating your material since it doesn’t retain any chemicals after application. You will be able to do more prints with the same amount of solution.
Use a syringe or a small cup to pour the chemicals onto the rod. Alternatively, pour the solution in a line onto the top of the paper. Pull the rod back and forth a couple of times over the material until it is covered. This method is a little tricky to get the hang of, but once you do, it works very well.
The dip method
You can pour out the solution in a tray, and submerge the material. Keep your gloves on and move the paper or fabric around the tray until it’s fully saturated. If printing on fabric squeeze as much excess liquid out as possible before hanging it to dry. If printing on paper, drain away as much excess fluid as possible before hanging.
More chemicals will be used with the dip method, but you’re pretty much guaranteed an even coating. Just make sure you don’t get streaks when you hang it to dry.
Once you’ve finished coating the material, dry it in a completely dark area. It is now sensitive to light and will begin to “fog” or change color if it is exposed to light. You can dry the material by hanging it on a plastic clothesline, pegging it with plastic pegs, or on a flat surface. If you have problems finding a dark room, a chest of drawers or an airing cupboard may be the solution. To speed up the drying process a hair dryer or a hot air fan can be used on moderate heat.
If you hang very wet material, be aware that the chemicals may cause both streaks in the final print if the chemicals run, and stains on the floor below. Before leaving the material to dry, don’t forget to clean up! Wipe all surfaces and remove any spillage or splashes. Any chemicals left can cause a nasty stain.
When the chemicals are applied to white material it appears greenish yellow when dry.
The dried material can be stored for later use, but some oxidation may occur and the final print can be dark blue on lighter blue, rather than blue on white.
Skip the drying and wet process
If you don’t want to wait for the material to dry you can try wet processing. This is done by simply exposing the material to UV light with your negative or objects placed on top when still wet.
However, do not use a negative you only have one precious copy of. The sensitizer contains chemicals that can damage a negative when wet. If you are making photograms and placing objects on the material it may also stain them, depending on the material they’re made of. So, think twice before you put antique lace or other valuable objects in contact with wet cyanotype chemicals.
Storing coated material
Coated material will not stay fresh forever. It can however be stored for around six months without too much effect on the final print.
If the coated material has turned dark green when you pull it out of the bag, it is likely to have oxidised. Using aged material will result in light blue highlights instead of what should have been a clear white. The print will therefore have less contrast. There is not much to be done about this apart from starting all over again and coating a new batch. One thing you can try is to soak the print for an hour after the final rinse.
To prolong the storage time of coated material as much as possible, make sure it is completely bone dry when storing it. Keep it in a black, light proof bag (those used for photographic paper are great) and press any excess air out of the bag before sealing it. Keep the bag in cool and dry place.