Making a stop-motion animation using clay is hard work. Normal movies use 24 frames per second (frame/s). Animation usually uses "doubles" or "twos"; that is using two frames for each shot. This means that 12 changes are made for one second of movie. For a 30-minute movie, there would be about 21,600 stops to change the objects for the next frame. For a full-length (90-minute) movie, there would be about 64,800 stops. IF some of the parts were done with only a single, not double frame, there would be even more stops. Great care must be taken to make sure that the object is not moved by accident. For full-length movies, animators now use rubber silicone and resin-cast objects. One foam-rubber method has been called "Foamation" by Will Vinton.