Obviously, I wanted to make sure my paints were non-toxic and washable, so I made my own. It's easy! I gathered up some old markers from around the house, used pliers to pop off the back, pulled out the felt and put it into an inexpensive 8 oz. spray bottle. Then I added water and gave it a good swish. Within minutes I had a cheap bottle of parent-approved spray paint ready to go. I let the colors sit over night to make sure they were nice and bright before using them. In other words: FREE PAINT! Great way to reduce, reuse and recycle.
At the market, I offered everyone stencils. It takes a light touch, but you can get a nice affect by spray in the paint over them. Of course, not everyone is interested in precision. Some kids wanted to just have fun mixing colors and seeing what happened! That's why I like to make sure I have all the primary colors available.
To look at the process from the other side, I offer kids coffee filters. They used washable markers to make designs, then sprayed with plain water, causing the ink to spread and blend. It's a lot of fun. I especially like using the black marker, because all the pigments separate, showing the blues and greens that make up the black ink. This is a really fun way to introduce children to chromatography!