This is an idea that came from DLTK crafts for kids — they made a coffee filter planet earth.
If you draw with felt pens on coffee filter paper and then spray or sprinkle water on your drawing, it gets nice and fuzzy. Perfect for making weather paintings, satellite images or even a collage. This would also be a good way to make a Foggy diorama.
The shape of the filters we have make a natural rainbow shape — cut off the sealed side and bottom and unfold. Cut circles for suns & planets (or just flatten them, if that's the kind of filter you have).