You do not need to let your child make a mess in order for them to have fun and learn with a sensory bin. Part of sensory bins is learning rules. As they learn these rules, stay close. If they start to dump, remind them of the rules and offer a chance for greater success. If they dump again, take the bin away. Remind them of the rules and let them know they'll get have another chance another time. **Give them another chance. 5 minutes, 5 hours, 5 days... let them try again.