Most die casters rely on spray to establish the correct die temperature to make good parts. This is not surprising. Evaporation of water quickly removes a lot of heat. A skilled manual die cast operator effectively targets and cools the hot spots with his spray wand. Most of the spray is used is water. Release agents are mixed with the water and form a thin coating on the die surface when the water evaporates. A typical release agent contains bactericide that prevents bacteria growth when it is still a concentrate.

Die casters who specialize in high volume parts have discovered that automatic sprayers have multiple spray heads. When properly implemented they reduce the amount of cycle time accomplishing spray. This assumes that the spray heads keep spraying. (plugged spray heads do not cool their portion of the die) Many shop try to mitigate spray nozzle plugging by flooding the die. I agree that the nozzles stay working longer running wide open at the expense of porosity in the casting and wasted lube.

I prefer to attack the causes of plugged nozzles. One of the big causes is bacteria growth in the spray. Water based die lubes are designed to be biodegradable when diluted with water. While this helps the environment, it causes a lot of sprayer plugging. As a minimum dumping a gallon of chlorine bleach into your central mixing system monthly is recommended. I prefer using the silver bullet. (silver ions inhibit bacteria growth) Systems that electrically add silver ions to the central lube mixer feed water, are a more effective answer. (these are sold for treating swimming pools) Bacteria growth prevention is best applied to every casting made.