In a dish (such as a bowl) place a large cinder or pieces of charcoal, porous stones or pieces of brick. Mix together six tablespoons each of water, table salt and bluing. Mix well and let stand an hour. Then add one tablespoon ammonia. Stir briskly. Pour over cinder, charcoal or stones. To give color, add drops of cake coloring here and there. Place it where it won’t have to be moved or bumped so the formation won’t crumble. More solution can be added when action stops, which may not be for a week or ten days. Add carefully at the sides.