Simply put, a cyanotype is an artwork created when the sun causes some parts of a surface (paper, fabric, etc.) to react which then differs from the part left in shadow. You end up with a blue-tinged shape made by that shadow. The first blueprints were made by cyanotype process. It's why they're blue.
If you lay a bike gear down on a piece of paper, you get the shadow of the bike gear. If you lay a cinnamon fern down on a t-shirt, you end up with the shadow of that fern.
Why does the fabric or paper react with the sun like that? It is because you painted the surface with a photo-reactive substance.
You start by mixing up the cyanotype solution. There are two parts to this. One part is an 8.1% solution of potassium ferricyanide. The other part is a 20% solution of ferric ammonium citrate. You keep those two solutions separate until youíre ready to start the cyanotype process. When youíre ready, you mix equal parts of those two solutions together. You use that mixture like a paint to paint the paper, fabric, or other item you wish to work with. You need to dry the item in total darkness Ė otherwise itíll start reacting to light all on its own.
In an hour or two, the object is dry and ready to expose.
Once the painted object is dry, you take it out into the sun and put items on top of the paper (fabric, etc.). It usually takes ten to twenty minutes for the image to set, depending on how strong the sun is where you are.
Once you're happy with the exposure level, you rinse the object for a few minutes to get rid of any extra liquid. That sets the image. Wherever the sun was able to touch turns a rich, vibrant blue color.
You can make the designs with anything that will block the sun. So you can make cyanotypes with gears, keys, plants, hands, feet, you name it. It has to be something thatíll stay still for the 10-20 minutes so the shadow is etched.
You can buy pre-made cyanotype paper on the web or mix your own solution to paint with. Either way, give cyanotypes a try. They offer great amounts of fun!