I found out the reason that they do not add anything to the paint is becuase it will break down the paint over time in the bottle. They want the paint to stay good and not really have a shelf life. This I really like because you never have a clue how old a bottle of paint is until you but it and then try to use it, money wasted. So when you add after it helps then, not needed but personally it like how much it improves the flow and leveling of the paint.