I got a gallon of black latex paint and mixed it with a large jug of Elmer's glue and a couple cans of shaving cream. I then squirted some saline solution (a little at a time until consistency that you like) and mixed it up. It made a nice thick, slimy goo that was so fun to play in. Cost was about $30 or so. If you add too much contact solution, it become too rubbery. Someone commented that vinegar can reduce the rubbery consistency. It sticks to your body but washes off easily with a little scrubbing.