A simple little spray can, with a simple task -- keep hair in place.
Why do they need so many different things in there?
Hair sprays are formulated to hold hair in place and keep it shiny,
without flaking off, without failing in humid conditions, and yet
retain the ability to be washed out of the hair easily for at least
Complex polymers are needed to perform all of these tasks well.
The basic building blocks of these polymers are the same ones found
in acrylic paints and white glue, but they are put together in such
a way that they are flexible, shiny, non-clogging in the spray can
nozzle, dry quickly, and remain waterproof yet able to be washed out of
The two main polymers used are
Vinyl Acetate/Crotonates/Vinyl Neodecanoate Copolymer,
(a form of
vinyl acetate) and
Octylacrylamide/Acrylates/Butylaminoethyl Methacrylate Copolymer,
a form of
These polymers are carried in a base of water and
alcohol (usually denatured), and the
liquified gas dimethyl ether
which acts as the propellant. The dimethyl ether boils away as
a gas when the spray head is pushed down, propelling the rest of the
ingredients out in a fine mist.
The emulsifier aminomethyl
propanol serves several purposes in hair sprays. It acts as
a "buffering" agent, controlling the acidity of the mixture to
make it neutral ("pH balanced"). It also helps keep the polymers
mixed with the water and alcohol, and controls the water-solubility
of the final mist, giving it the humidity-resistance needed. It
also helps to form the polymers into a gel.
Sodium benzoate is used as a
preservative, although it also functions as a corrosion inhibitor.
Cyclopentasiloxane is a volatile
used to make the film water repellent, and to eliminate tackiness.
It is a thickener; it acts as a lubricant and gives the resulting
coating a silkier feel.
is a moisturizing agent, drawing moisture from the air and holding
Some sprays include vitamins such as tocopherols (Vitamin E) or
panthenol, which is metabolized in the skin to become pantothenic
acid, a B vitamin.
Since hair does not metabolize (it's dead, Jim), these perform
the functions of anti-oxidants (tocopherols), and add shine and
moisture (panthenol), rather than perform their normal vitamin
roles. Moisture helps prevent damage during combing.
Hydrolyzed soy proteins are also sometimes added. These are
more commonly known as soy sauce and MSG (monosodium glutamate),
an amino acid.
Butylene glycol is sometimes used as
a humectant (moisturizer) and preservative if the spray contains
food items such as vitamins and proteins. It also helps to retain