You can use a kitchen sprayer or hand-held shower head to get soap and shampoo out of your hair. A push-and-release nozzle will shoot a steady stream of water, while finger controls on other models let you regulate the amount of pressure. Cold cleaning agents and beauty care products are often sold in plastic bottles with caps that release a fine mist when you squeeze them. Other liquids, like pine oil, are packaged in bottles fitted with tiny nozzles that release a spray when you press the top down. A more common use for these bottles is to dilute concentrated substances that would otherwise be too powerful to handle—such as pine oil—with water. Early spray bottles made before the middle of the 20th century used rubber bulbs that had to be crushed to produce a spray; they were filled by hand and air pressure was used to pull liquid from the bottle. And, since it was cheaper to buy an entirely new bottle of Windex than it was to buy sprayers separately, people would reuse the same sprayer for several years. But as plastics improved, and manufacturers began putting sprayers inside all their bottles, consumers could start buying replacement parts instead of having to replace the entire bottle every time they needed a new nozzle.