Mascara coats the lashes to make them darker and lengthens them and/or volumizes them. In addition, mascara provides a contrast, better emphasizing the surrounding whiteness of the eye which makes you look younger.
Mascaras are generally either an oil-in-water emulsion, which makes it easy to wash off with water and cleanser, or solvent based which is waterproof and needs a makeup remover or oil based product to remove.
Mascara contains color, usually black but can be brown, blue, or even purple! The color can either come from color dispersions which are very easy to incorporate into mascara formulations or pigment in powder form. Some mascara formulas are clear, no pigment, and are used to define the lashes without color for a natural look.
Film formers are very important in mascaras because they help the mascara adhere to the lashes and aid in long wear properties. There are water based film formers and oil based film formers. If you have both a water phase and oil phase in your mascara formula, it is ideal to have both a water based film former and an oil based film former. If you can only have one film former in your formula then choose the water based film former. If you are trying to formulate a long wearing mascara, you can have more volatile, more wax, and more film former in your formula.
Mascara also has viscosity boosting ingredients. You do not want a mascara formula that is so thin that it drips from the mascara brush. Viscosity boosting ingredients include waxes, polymers, and clays. Preservatives are essential to a mascara formula because you do not want harmful bacteria/fungi to grow that can irritate and cause eye infections.
Mascaras can also contain conditioning agents, but they should also have either lash lengtheners or volumizers. Polymers that dry fast are good for lengthening because as you coat the lashes, it lengthens and then freezes. If you have fibers in a lash lengthening mascara, then you want longer play time so you can align the fibers as you brush the mascara from base of eyelashes to the tips. You can increase the play time by having lubricious materials. However, lengthening mascara usually does not contain many fibers; it is volumizing mascaras that contain fibers. The average amount of fibers you would use in a mascara is 1% but you can go up to 3%.
The brush is also critical to the formula. Different brushes can dramatically affect the formula. I would go as far as to say that a successful mascara is credited to 50% brush and 50% formula.
Liquid eyeliner formulas are similar to mascara formulas except that they are thinner and do not contain volumizing or lengthening ingredients.
