6 tbsp. bluing
6 tbsp. salt
6 tbsp. water
1 tbsp. ammonia

Stir bluing, salt and water and let stand 1 hour. Add ammonia. Pour over coal. Add 1 tablespoon water twice per week. Add food coloring after it starts to grow. When through with coal garden, wrap and throw away. Do not flush down the toilet or pour it down a drain, it will keep on growing.