What are the components of a nail varnish?

For a special occasion or simply to bring a bit of colour into one's daily life, nail varnishes are among the most popularly used products. There are various types (matte, glossy, semi-permanent, permanent...) to suit everyone's needs and desires. The use of nail varnish is older than one might think: archaeological excavations have unearthed nail varnishes dating back to 6,000 years before our era. Of course, at that time, the formulations were very different. In ancient China and Egypt, henna leaves and clay were primarily used to dye nails in a brown-red colour, a symbol of high social status. It is even said that Queen Nefertiti, wife of Pharaoh Akhenaton, often sported ruby red nails. Today, nail varnishes are mainly composed of solvents (≈ 70%), film-forming polymers (≈ 15%), thermoplastic resins (≈ 7%), plasticisers (≈ 7%), pigments (≈ 1%) and suspension agents (≈ 1%).

Solvents: the liquid foundation of nail varnishes.

Nail varnishes are primarily composed of solvents, necessary to ensure the blending of various ingredients and achieve a fluid and easy-to-apply texture. Solvents also ensure the gradual evaporation of the product after application, leaving a solid and uniform layer on the nail. The main solvents used are ethyl acetate and butyl acetate, volatile solvents that evaporate quickly after the application of the nail varnish, which is convenient for speeding up the drying process. Well known for its role in nail-varnish removers, acetone is also sometimes used in small amounts in varnishes to improve their fluidity. However, it is quite harsh on the skin and nails and tends to dry them out and weaken them. Solvents are essential to the formulation of nail varnishes but are responsible for the strong smell of these products which can sometimes bother sensitive individuals, such as pregnant women.

Polymers: The structure of nail varnishes.

Without polymers, nail varnish would not be able to form a solid film on the nail. These molecules are therefore essential for ensuring the adhesion, shine, and durability of the varnish. The key ingredient in most nail varnishes is nitrocellulose, a film-forming polymer that creates a thin, resilient layer. Nitrocellulose also imparts a natural glossy effect to varnishes in which it is incorporated. Historically, this polymer was the first medium used for cinematic films and was notably employed in the first reels of the Lumière brothers at the end of the 19th century. Acrylic copolymers are frequently added to nitrocellulose in nail varnishes, to enhance their flexibility and adhesion and prevent them from chipping too quickly. However, nitrocellulose is sensitive to heat, which explains why some varnishes thicken over time.

Plasticisers: to prevent nail varnishes from breaking.

When it dries, a nail varnish must be hard enough to withstand daily wear and tear (hand washing, use of household products, etc...) but not too rigid, so as not to crack at the slightest movement. This is where plasticisers come into play, molecules that make the texture of varnishes more flexible and resistant. However, the majority of plasticisers are controversial. Notably, dibutyl phthalate (DBP), considered a potential endocrine disruptor, camphor, which is irritating in high concentrations, and triphenyl phosphate (TPhP), which also raises concerns about its impact on the endocrine system.

Resins: for enhanced nail varnish adherence.

Often less known to the general public, resins are nonetheless important compounds for formulating a nail varnish. They enhance the adhesion of the varnish to the nail and provide a glossy and uniform finish. The resins commonly found in nail varnishes are formaldehyde resins, which are controversial due to their potential irritant and carcinogenic properties, acrylic resins, and alkyd resins.

Pigments and pearlescent substances: essential for nail varnish colour.

Nail varnishes come in a multitude of colours and finishes thanks to the pigments and reflective particles they contain. The most popular are iron oxides and titanium dioxide, mineral pigments, used to achieve red or white shades, micas, providing a pearlescent or metallic effect, and organic dyes, used to achieve bright colours. It's worth noting that dark and highly pigmented nail varnishes are often more difficult to completely remove from the nail surface.

Note : Some nail varnishes also incorporate active ingredients to care for the nails, such as green tea, known for its softening properties, durian, recognised for its ability to strengthen keratin, or the avocado oil, which has a nourishing effect.