This fabric dye works exactly like those hypercolor t-shirts that changed color when exposed to sunlight, except with permanent results. So if you're still shooting with a traditional film camera, you can actually develop your negatives onto a shirt and wear your shots proudly, instead of going the photo paper route which usually get buried in an album.
Available in a $35 set of three almost primary colors (red, blue, and orange) the dyes can be mixed to form other shades, and can be applied to any fabric or paint-friendly material using a regular brush. When placed in a bright light source such as sunlight for about five minutes, the exposed areas darken, letting you do fun things like expose film negatives.
Once you're satisfied with the results you just give the tee a good scrubbing with soap and water which will remove all of the remaining undeveloped dye. Looking at the results it seems as if you'll need a really high-contrast negative to get a decent image, but the process is infinitely easier than screen printing for making custom shirts. I should know, I've been using a similar dying technique on my own shirts for years now, but using spilled ketchup and mustard. [Photojojo]