Through this thaumaturgical ritual, the practioner can pour a special pitch-black oil into a pool of water and making the water solid black. It can not be seen through but it has no other effect. It will remain black until the effect is dispelled, the water evaporates or the water is diluted with a larger body of normal water.
One pint covers a small swimming pool size area. It last for a week and a large amount can be prepared at one time.