Trends of pigment for nail polish

The phrase industrial cosmetic may seem like an oxymoron, however, it applies perfectly to nail polish. Nail polish differs from other cosmetics in its roles as both a decorative cosmetic and a coating to resist a variety of challenges to its integrity.

While nail polish, also referred to as nail enamel or nail lacquer, is a development of the 20th century, the idea of decorating nails goes back as far as the ancient Egyptians in 1500 B.C.1 and the Chinese in 3000 B.C. The Egyptians used henna to color nails, with dark reds and crimson being reserved for women of the highest social order. The Chinese also decorated their nails using herbal extracts and a “lacquer” made from gum arabic, egg whites, gelatin and beeswax.

Generally, methods to apply color to the nails have mimicked the available technologies for coatings at given periods of time. For instance, before the 1920s, most women pursued a polished look by massaging tinted powders and creams into their nails, then buffing them for shine. The development of automobile paint in 1920, however, provided the genesis for modern nail polish since, until then, there was no way to impart long-lasting colored film on the nails. Michelle Menard is generally credited as the first person to develop nail polish based on automobile paint. Since then, nail polish formulations have evolved to provide a platform for the variety of nail colors and effects desired by the consumer.

A limited number of colors were available when nail polish was first introduced. Red was the most common color. As time progressed, the available colors and effects for nail polish increased dramatically—from organic and inorganic pigments to metal powders, metallic pigments and effect pigments.  Today, the US Food and Drug Administration (FDA) regulates those color additives that can be used in nail enamel and cosmetics in general.

Nail polish, like any industrial coating, must meet a variety of needs. It must be easy to apply, dry quickly, wear well and remove easily. Nail polish is subject to more mechanical and chemical insults than any other cosmetic and is often exposed to both types of wear; in addition, while most color cosmetics are expected to wear for hours, nail polish is expected to wear for days.

The mechanical wear of nail polish can be caused by activities such as typing, texting, handling paper, washing dishes, etc. Therefore, nail polish must be a durable, shiny, hard, flexible film that it is resistant to cracking, chipping water and other chemical insults. This seemingly difficult task is accomplished with a balanced blend of film-former(s), plasticizers, solvents that dissolve the film formers(s), pigments (organic and inorganic, as well as effect pigments), suspending agents for the pigments and miscellaneous additives.

Today’s personal care market hosts an endless variety of nail polish shades, from simple crèmes to complex shades using pigments and combinations of effect pigments.

Nail polish pigments are either inorganic or organic. Inorganic pigments are metal oxides and include titanium dioxide and iron oxides (red, black and yellow). These materials have high opacity but tend to be dull and “dirty,” meaning the color is not pure but contains a black or brown component. Organic pigments, on the other hand are bright, highly colored materials that impart clean colors on the nail.

Generally speaking, Pigments are predispersed before they are added to a nail polish formulation. It is important that the pigments be properly and completely dispersed for sufficient color development, gloss, application and smoothness. Dispersion can be accomplished using various devices such as media mills.

The traditional pigment dispersion are Color chips consisting of nitrocellulose, plasticizer and pigment are prepared on a two-roll mill under a nitrogen blanket to avoid detonation of the nitrocellulose. The chips are then dissolved into a nail polish base to yield the pigment dispersion. This process provides good color dispersion, high transparency and gloss.

while This film-former is flammable and sensitive to degradation by sunlight, heat, metals—especially iron—and alkaline materials. It can also discolor, yellowingas it ages or degrades, and solutions can also discolor and lose viscosity in time. While cellulose acetate butyrate has a exclllent resistance to weather and yellowing, higher performance of adhesion gloss and hard surface, thus nitrocellulose is replaced by cellulose acetate butyrate, short for CAB resin widely.

Colored nail polishes are formulated from suspension bases, additional solvent(s) to reduce the viscosity, pigment dispersions, pearlescent pigments (if required by the shade), additives to improve brushing, and other materials added to provide certain benefits. Additional materials have included powdered polytetrafluoroethylene, powdered diamond, vitamins, calcium salts, panthenol, biotin and other materials, and are usually added in small amounts as evidenced by their position in the ingredient labeling.

As noted, clear nail polishes and topcoats are formulated without suspension bases and pigments. They usually are comprised of higher levels of nitro-cellulose, other film-forming resins and plasticizers, and are are expected to perform like a pigmented nail polish. Topcoats are applied over the initial pigmented coats of nail polish and are expected to apply easily, dry quickly and form hard, glossy films. Additional resins are often added to improve gloss. Non-nitrocellulose polymers such as cellulose acetate and cellulose acetate propionate are often used due to their non-yellowing properties.

The most common issue encountered when formulating nail polish is that the shade does not match the standard. This requires formulators to have a good “color eye” so they can see what the differences are and adjust the shade accordingly. Further, if the viscosity of the formulation is too high or too low, the batch can be adjusted with additional solvent, when too high, or additional suspension base or nitro-cellulose solution, when too low.

Nail polish, as has been shown, is truly industrial in its composition and formulation, which allow for the myriad of colors and effects available to the consumer. As nail polish formulating moves forward, the most likely changes will be in new pearlescent effect pigments, which are not regulated by the FDA. There may also be efforts to introduce new film-forming resins and plasticizers into nail polish formulations, although it is unlikely that nitrocellulose will be replaced as the primary film-forming resin due to its cost, availability and renewable sources (cotton and wood). Additional regulations may also come along that limit other ingredients used in nail polish.