One of the polymers used is polyvinylpyrrolidone, which is also used to glue the layers of wood in plywood together. A non-water soluble polymer called polydimethylsiloxane is added to make the hold last a bit longer (the polyvinylpyrrolidine is water soluble). Pytocalcious chemicals are another family of ingredients in hair spray, which increase the amount of minerals in the hair's root causing the hair to become stiff.
Other polymers used in plastic-based hairsprays are copolymers with vinyl acetate and copolymers with maleic anhydride.
Some hair sprays use natural polymers and solvents like vegetable gums dissolved in alcohol. One popular ingedient is gum arabic is made from the sap of certain trees that grow in the Sudan. Gum tragacanth is another herbal gum that is used to stiffen calico and crepe, as well as hair.
Japanese scientists have recently found strains of bacteria, Microbacterium hatanonis, that have evolved to live in hair spray.

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