The first part of our project was to draw in reverse using a Sgraffito technique, also known as scratch art, on a clear sheet of plastic coated with ink. This can be purchased prepared for you, or you can make your own with waterproof ink. (A variation is to draw or paint with ink on a clear sheet.)
The scratch tools must be sharp enough to draw easily, or it's not much fun! Before class, I whittled dowel rods down to a point, and students used sand paper to maintain the point while working. (Of course, we always remember our safety rules with these sharp tools.)
Next, we were ready to transfer our drawings to sunprint paper. The clear sheet with the ink drawing was laid directly over the photo-sensitive paper and exposed to direct sunlight. All clear areas where the ink had been scraped away allowed light to reach the sunprint paper, creating a polarized, or reverse, image.
Also called nature print paper or cyanotype paper, sunprint paper can be found at many art, craft, and science suppliers. The paper is coated with a non-toxic chemical that turns a brilliant blue color after being exposed to sunlight, rinsed in plain water, and air-dried.
Final art work can be treated like watercolor paintings, that is, keep dry and protect from gradual fading caused by direct sunlight over time.