Splatter painting is something that the teens are always wanting to do with acrylics, and I usually say “No Splattering.” However, it is really enjoyable, and splattering creates fun, spontaneous images. Watercolor is the perfect medium for this activity because it splatters well, but is easy to clean up. We happened to have some leftover liquid watercolor and black ink, which worked out great.
If you want an inexpensive paper, you can cut down cheap poster board and use the mat side. Watercolor paper is a little pricey, but worth it. I was surprised by the speed at which people completed their paintings. It might be a good idea to have lots of extra paper, in case everyone wants to make more than one. In addition, you might want to think of another process to add to increase the complexity. We had straws out so that people could blow on their wet paint to create spidery designs, but collage or stenciling might be fun too.