Christina McFall over on CRAFT has a great tutorial on using the cyanotype printing technique on textiles like handknits and crochet.
Cyanotype is a fun printmaking technique that is well-suited for printing designs on hand knits and crochet as well as other fabric. While the nature of cyanotype limits the print to shades of blue*, the deep indigo blue is beautiful printed on different colors of yarn and fabric. The process is inexpensive, simple to get started, and relatively low-toxic, making it a great printing method for crafters and artists alike.
Most people are familiar with cyanotype without knowing it – in the form of the blue sunprint papers for kids. However, instead of buying pre-treated paper, you can buy the cyanotype sensitizer and use it to treat just about anything. The cyanotype image is formed when fabric that has been coated with the sensitizing solution is exposed to UV light (sunlight). Where the light penetrates to the sensitized surface, a dark blue permanent dye is formed, and where the light is blocked, the fabric stays its original color. So with the use of a negative (like an old black and white photographic negative), you can print any image or artwork. Fortunately, it’s easy to make digital negatives with a computer and inkjet printer.
In this tutorial, I will show you everything you need to know to get started making your own cyanotype prints on hand knits. The process is essentially the same for any other type of fabric or paper, so experiment and have fun.