This is really cool and super quick/easy. Combine the following in a little bowl:
Then add some water to make a nice smooth paste. I think it was bout 2-3 teaspoons of water.
Paint away on a nice thick sheet of cardboard (if you don't have enough paint brushes use cotton buds - they work really well). For the cardboard, you can cut up some cereal boxes and use those. Make sure when they paint that they have globs of paint or else those parts won't puff up.
Microwave the design on high for 10 - 30 seconds until the paint puffs and it's all nice and dry. We did ours for 30 seconds.
(ignore the grease spots...it was from a cracker box.....)
I loved how they puffed up a bit and then hardened. We didn't have to wait forever for them to dry and they hold pretty well for when kids like to carry them around and show off their artwork.
You can find this awesome post linked up to the following Fantastic Parties: