I've been bitten by the cyanotype bug again. I was hit by it hard last spring and apparently it's a spring thing for me! Cyanotypes are (according to wikipedia, since they do it better than me) "a photographic printing process that produces a cyan blue print. Engineers used the process well into the 20th century (i.e. blueprints) as a simple and low cost process to produce copies of drawings. The process uses two chemicals: ammonium iron citrate and potassium ferricyanide."
You don't have to become a temporary mad scientist to use it. Kits are easily available online; Jacquard makes a good one called Sensitizer Set and I know there are other ones too. All you have to do is mix equal portions of the two bottles, and you're good to go. I use a foam brush, but a Japanese hake brush is often recommended. It really doesn't matter, as long as you get the results you want. You paint it on whatever paper you want. Use a paper though, that will hold up to the washing. I like to use medium weight printmaking paper, but almost any printmaking paper will work pretty well.
You can prepare your paper inside, best under low light, I prepare a bunch, then let them dry in a couple of cabinets that have shelves. I can store them there until I want them-- you do want to store them in a lightproof area. Next step is to place the objects or transparency that you want to use on top of the paper, and sandwich it between a bottom layer, like plexiglass or cardboard, and place another piece of glass or plexiglass on top. I like to use glass because it's got some weight to it, so it really keeps the image tight against the paper.
Place it in a sunny spot outside, and wait! When it turns a tan color it's ready; check the instructions on the kit for better info. I like to mess around with exposures and paper, so I'm not going for a crisp image.
Once done, submerge the exposed paper in a pan of water and agitate it gently. Adding a little hydrogen peroxide to the water will help hasten the blue along. When blue, take it out, blot it, and let it dry. That's it!
