Water-based hair products: (e.g. gels, mousses and foams)
These deliver the styling polymers in a water base, so they tend to dry relatively slowly. They coat the hair in a film which, as it dries, becomes sticky. This lends friction to the hair, making it easier to style. Once the product dries on the hair it forms a hard film that holds the hair in place. This film is rigid and non-flexible, so further brushing or disrupting the hair style will potentially break the bonds that hold the hairstyle in place, although the product on the hair shaft will still provide some degree of friction which will help with further styling until the product is washed out.
Gels are thick water-based styling products that are particularly good for increasing hair stiffness and providing a texturized look. Gel is popular for short, spikey hairstyles because it provides good root lift.
Mousses and foams deliver the water-soluble styling ingredients with the aid of liquid propellant. The propellant quickly evaporates once the mousse is dispensed into the hand leaving the styling concentrate. Because the styling concentrate is essentially "whipped up", it is able to be easily dispensed throughout the hair and spread thinly so that it doesn't weigh down hair or create areas of excessive rigidity.
Wax-based hair products: (e.g. waxes and pomades)
Wax based styling products differ from water based products in that they don't actually dry (since they're not wet in the first place — just waxy). This enables you to create the same thick, defined, piecey look as with gels, but without the rigidity. Since these products remain pliable, you're able to fix and restyle your hair throughout the day just by running your fingers through your hair.
Waxes and pomades are highly flexible and provide great definition, but can be heavy when used in inappropriate quantities, or on hair that is fine or prone to oiliness. They can also be difficult to wash out, so it is beneficial to use a good clarifying shampoo if you're using waxes or pomades regularly.
Alcohol-based hair products: (e.g. hairspray)
Alcohol based styling products, such as hairspray, deliver styling product to the hair as a mixture of styling product and alcohol. The alcohol component of the mix evaporates very quickly, which means that these products will dry on the hair much faster than their water-based counterparts. Alcohol-based products typically use aerosol propellants which enable the styling product to be delivered in very small droplets, which dry faster and provide a more even, thorough coverage. Alcohol-based stylers are excellent for finishing off a style because they do not rewet the hair (which can be detrimental to the style), and because they effectively seal off the hair from the weakening effect of external moisture and humidity.
