Any gel product that can be soaked off with acetone.

Any gel product that can NOT be soaked off with acetone, and must be filed off in order to remove. Sometimes even a top coat is a hard gel - less penetrable and hard wearing; and must be filed off in order to perform the soak-off process.

These gels add strength to the nail structure for longer and resilient wear. BIAB (builder in a bottle) is a similar product with a thinner formula in order to be used in bottle form.

When gel cures, the surfaces that are exposed to oxygen remain uncured; this tacky layer is known as the inhibition layer. It helps to adhere the next layer of gel. Sometimes, different brands will be incompatible with other brands’ inhibition layer, and an indicator of that is when the gel “shrinks” or “craters” during application. When working with various brands, it is important to wipe off the inhibition layer so it doesn’t contaminate the formula of the other brands.

When a product is described “Non-wipe,” it cures without leaving any sticky residue. It is often the final top coat layer.

Most gels (with exception to nuance art/texture gels) will self-level with the help of time and gravity. It promises the smoothest possible surface finish.

Viscosity will help determine how much time it’ll take to achieve a perfectly levelled surface. Viscosity is resistance to flow, therefore, low viscosity means low resistance (flows easily), and high viscosity means high resistance (thick, slow).

A smaller, single-reactive monomer used for its adhesive properties and ability to create strong bonds in most gel products. Due to its small molecular size, it is a skin allergen and the leading cause of contact dermatitis for a lot of DIYers and even nail technicians, developed due to overexposure on the skin.

A larger, di-functional monomer (containing two reactive sites) that increases the flexibility of the cured gel polish and reduces chipping. Di-hema can also cause contact dermatitis, but less likely due to its larger molecular size and lesser penetration into the skin.

A monomer that helps gel harden properly under UV/LED, and improves flexibility and adhesion. Reactions are often delayed and increasingly develop sensitivity over time.

Another methacrylate monomer, similar in function to HEMA, and adds flexibility, adhesion, and smooth application in gels. HEMA-sensitive clients must avoid HPMA as well.

A photoinitiator that helps gel cure faster and more evenly; key for “fast-curing” formulas, reducing under-cure risks (safety!). TPO isn't a major allergen, but inhalation of dust from filing cured gel can irritate some people, and for this reason is banned in the EU.

TPO is a common ingredient in HEMA-FREE products. Manufacturers may switch to “TPO-L” (ethyl trimethylbenzoyl phenylphosphinate), an alternative photoinitiator, not banned in the EU.

A tri-functional acrylate monomer (meaning it has 3 reactive acrylate groups). Commonly used in gel polishes and builders to create a strong, durable cured surface. It helps the gel cure harder and improves chemical resistance. Improves strength and reduces tackiness after curing. Has low viscosity, so it’s often used in thinner consistency gels.