Sandy Donabed mentioned on her blog that she had bought a box of chipboard letters at TJMaxx and was thinking about using them for sun printing. I had seen the same box of letters at our TJ and carried them around the store for awhile, trying to figure out why I needed them. I didn't buy them, but then Sandy mentioned that great idea and I went right back and bought them in two sizes. And I finally got around to trying them out today.
I painted a piece of fabric with fabric paints. Setacolor paints advertise themselves as being "sun paints" but really any kind of fabric paint, probably any kind of acrylic paint for that matter, will work the same.
Once it is dry, remove the letters and shake off all the salt.