Why Is Milk White?: & 200 Other Curious Chemistry Questions (2013)
3. Household Chemistry
How do people make lipstick different colors?
Most lipstick pigments are shades of red. The most popular red pigment used in lipsticks is carmine, a dye made from the shell of a tiny scale insect that lives on cactus in the US Southwest.
The dye itself is carminic acid, which is used in many foods and cosmetics. It is sometimes called cochineal extract. Only the female insect has the dye—a natural defense to keep other insects from eating the little critters. They sit on the cactus with their little straws sipping cactus juice, looking like little scales (which is why they are called scale insects). They can’t run away, so they make carminic acid, which other bugs don’t like.
Cochineal extract is also used in fruit juices like ruby red grapefruit juice, strawberry orange juice, pomegranate cherry juice, and many others. Like any other natural color derived from living things, cochineal extract usually contains some proteins from the original source, and some people have allergic reactions to the proteins. For this reason, and because some people don’t like the idea of eating bugs, some manufacturers are moving to synthetic dyes like FD&C Red #40. But that dye has a slightly more orange color.
Other red pigments used in lipsticks are made from iron compounds. In other words, the red comes from rust. Both red iron oxides and black iron oxides can be used. White pigment for pink lipstick comes from titanium dioxide or zinc oxide. Synthetic dyes such as D&C Red #6 are also common.
The size of the pigment particles has an effect on how the light hits the eye—and thus, how it looks. Mica particles coated with colored metal oxides are particularly affected. Particles smaller than 25 microns produce a silky effect. Larger sizes up to 50 microns appear pearlescent. Larger sizes than that appear brighter and sparkly. Some lipsticks have metallic silver, gold, or copper colors made from mica particles coated with pigments.