 Another wide use of spray bottles is mixing down concentrates such as pine oil with water.While spray bottles existed long before the middle of the 20th century, they used a rubber bulb which was squeezed to produce the spray; the quickly-moving air siphoned fluid from the bottle.The rapid improvement in plastics after World War II increased the range of fluids that could be dispensed, and reduced the cost of the sprayers because assembly could be fully automated.