At this point, stop stirring the mixture and remove the splint. It must not be handled until it is completely set, since it may contain unreacted materials. It will be ready to handle after 24 hours. Stir until completely dissolved. This may take 2-3 minutes.
Warm water works faster.
You are now ready to play with it and observe its properties. Keep in a plastic bag when not using it. Keep it off of clothes, upholstered furniture and varnished wood. They will decorate their model with food color, buttons, or any craft materials. Form a shape with the polystyrene cup and observe the shape after a 24 hours period.