The various types of nail polish.

As their name suggests, semi-permanent nail polishes stand out from traditional polishes due to their extended wear of two to three weeks. Unlike regular nail polishes that air dry, semi-permanent polishes require exposure to UV or LED lamps. This exposure triggers a polymerization reaction essential for hardening the polish layer. The application of a semi-permanent polish involves several steps: nail preparation with a degreaser to remove any oil, followed by the application of a base coat to ensure polish adherence. The color layer is then applied in several thin coats, each hardened under a UV or LED lamp. Finally, a top coat is applied to enhance the shine and ensure the longevity of the manicure.

The removal of a semi-permanent nail polish is a bit unique and cannot be done with just any remover. A special remover, often acetone-based, is required. This is applied to a soaked cotton pad, which is placed on the nail and left to act for 10 to 15 minutes. Once the polish has softened, it can be gently removed with a manicure stick, taking care not to scrape the nail too much to avoid damaging it. It is also possible to simply use a nail file to remove a semi-permanent nail polish, but this method tends to weaken the nails if not performed by a professional in a salon.

Semi-permanent nail polishes are a compelling option for individuals seeking a long-lasting and durable manicure.

Permanent nail polishes provide an even more durable and shock-resistant solution than semi-permanent polishes, allowing for a finish that can last beyond three weeks, sometimes up to a month. The main temporal limit then becomes the regrowth of the nails, which can make the manicure look unattractive after a certain time. Permanent nail polishes are applied in a similar way to semi-permanent polishes and require polymerization under UV or LED light. Although both types of polish contain durable polymers, which are responsible for their longevity, permanent polishes also use acrylic resins, allowing for the creation of a robust barrier. This resistance allows permanent polishes to remain intact even in the presence of heat, humidity, or cleaning products and not to show signs of wear for several weeks.

This durability, however, comes at a cost: it is impossible to remove a permanent nail polish without visiting a professional salon because no remover will completely take off this type of polish. Only a nail file handled by a professional can remove permanent nail polish. It is strongly advised against trying to remove permanent nail polish by oneself as improper removal could damage the nails.

Permanent nail polishes are favored by those seeking a highly durable and long-lasting solution. However, their removal can be inconvenient as it requires a visit to a professional salon.

Experiencing a surge in popularity, so-called natural nail polishes have been developed in response to the alleged dangers of traditional nail polishes. These polishes are identifiable by the label "n-free", where n represents the number of controversial ingredients removed. For instance, "3-free" polishes are formulated without toluene, dibutyl phthalate (DBT), or formaldehyde, while "5-free" polishes also exclude camphor and xylene. Natural polishes typically replace solvents with plant extracts, such as potato, cassava, corn, or sugarcane. "n-free" polishes cater to a demographic keen on avoiding potentially harmful chemicals. Aside from their composition, their application, finish, and removal are similar to those of traditional polishes.

Even though natural nail polishes are generally safer than traditional ones, it's important to clarify that terms like "3-free", "5-free", or "7-free" are not based on a universally established standard. This was notably demonstrated in a 2018 study that examined the composition of 40 "n-free" nail polishes from 12 different brands. The figure below illustrates the lack of uniformity in the formulas among these nail polishes. The differences are particularly pronounced for polishes that exclude more than 5 controversial substances.

Peel-off nail polishes distinguish themselves from other polishes by their simplified removal. Indeed, while they are applied in the same way as traditional nail polishes, the peel-off polishes are formulated to be peeled off the nail, hence their name. They contain specific polymers that, once applied and dried, form a flexible and durable film that is flexible enough to be removed in one go. This property makes peel-off polishes particularly attractive for those who wish to frequently change color without having to use a remover and who want to preserve their nails as much as possible. However, they are much less durable than traditional polishes.

Peel-off nail polishes can be simply removed by lifting a corner of the polish with a manicure stick or file and then gently pulling to peel off the film in one go. Kinder to the nails, this process also has the advantage of being very quick and offers great flexibility for changing manicures.

Peel-off nail polishes are highly beneficial for those seeking a gentle, convenient, and temporary manicure.

Thermal nail polishes, which are quite playful, have the unique characteristic of reacting to temperature changes and altering their color in response to these shifts. This phenomenon is made possible by thermochromic pigments, compounds that change hue when exposed to heat or cold. Most thermal polishes are semi-permanent, requiring exposure to a UV or LED lamp to harden, and are not easily removed.

After applying a thermal nail polish and allowing it to harden, you can experiment by immersing your hands in cold or warm water and observing the color changes that occur. Depending on the polish, you may see a transition from light pink to purple, from light blue to dark blue, or from yellow to green. Some offer an even broader color spectrum, ranging from white to dark gray.

By allowing the nail color to change in response to environmental interactions, thermal nail polishes provide an interactive and engaging experience.

Straddling the line between a treatment and a traditional nail polish, the hardening nail polish aims to strengthen and fortify the nail. The use of this type of polish is particularly beneficial between each application of polish or in cases of brittle nails, soft or split nails. The properties of hardening nail polishes come from the ingredients they contain, notably film-forming agents, such as nitrocellulose, which form a protective layer on the surface of the nail, thus limiting the evaporation of water from the nail plate. Other beneficial actives for nails can also be included in the formula of hardening nail polishes, such as keratin, vegetable oils or vitamins (B5 or E for example). Most hardening nail polishes are colorless, although there are also colored ones. This may seem paradoxical as it is then necessary to use a remover to take it off, which can weaken the nail, the opposite of the protective effect sought.

Nail hardeners are supplementary nail polishes that aid in strengthening fragile nails.