OK, the next part is a bit nerdy, but I couldn't help it. I'm a chemist.
The kit comes with 20 pieces of fabric (roughly 8.5" by 8.5" in size) pre-treated with potassium ferricyanide (K3[Fe(CN)6]) and an iron (also referred to as ferric) salt, ferric (III) ammonium citrate. When exposed to ultraviolet (or UV) light (like sunlight), the iron [Fe(III)] reduces (gains an electron) to Fe(II). The Fe(II) then reacts with the ferricyanide to form ferric ferrocyanide which is a blue dye known as Prussian blue.
So if you put something between the fabric and light source (a leaf, a puzzle piece, whatever) the portion of the fabric that is covered does not react so you're left with a white image on a dark blue piece of fabric.
OK, are you still reading??
Having never used something like this before, I did a few tests with stuff from the yard and from the kids toys. (I got a little carried away - it was so much fun.)
So now onto the artwork.
I took my son's original drawing and made a photocopy of it to shrink it since the original was larger than the fabric size. Using a transparency and a dark, permanent marker I copied the image to the transparency. (You can also put your image directly onto the transparency using a copier or printer.) Sorry the image in the photos isn't consistent.
Then you place a piece of cardboard down, with the fabric on top. Next place the transparency and finally a piece of non-UV filtering glass. (Do this inside - out of direct light, then take it outside.) Leave it outside for 10 minutes in the sun. And this is what it will look like.
Take it back inside and rinse it with water until the water runs clear.
Lay it flat to dry.
Now, what to do with the fabric?????
I'm linking this post to . . . . .