The Science of Gels

What’s really going on when your client puts her hand in the nail lamp? We explain what gel is made of and why it works so well.


ACTION: Apply bonder gel to the nail.

BEHIND THE SCENES: Functioning like an acrylic primer, bonder gel has the ability to bond both to the nail and to other gels, making the nail plate more compatible with the enhancement product.






ACTION: Cure nail in the nail light.

BEHIND THE SCENES: When the photoinitiator is exposed to the proper UV light wavelength and intensity, it gives off a fragment of a molecule called a free radical. This free radical makes the gel unstable as it reacts with the double-bonds of the resin. As the double-bonds break, they combine with each other to create the polymer that we know as the gel nail enhancement (which is now back to a stable state).


ACTION: (Sometimes) The client comments that her fingers feel warm or even pulls her hand out of the light due to a heat spike she feels in her fingers.

BEHIND THE SCENES: The polymerization reaction gives off heat, known in scientific terms as an exothermic reaction (“exo” means to give off, and “thermic” means heat). (The warm sensation is NOT caused by “friction between the molecules,” as some say.) If the heat is so intense that it causes the client pain, then the chemical reaction has occurred too quickly. Incompatibility between the gel and the gel light can cause this problem.



ACTION: Thinly apply builder gel. (Then repeat the curing process.)

BEHIND THE SCENES: UV light can’t penetrate deeply into most substances, including UV gels. UV light is typically absorbed by the upper layers of gel or may even be reflected away. When thick layers of gel are applied, they don’t let the light get to the lower part — which means it won’t cure properly. This is why you need to apply in thin layers, curing after each.




ACTION: Apply sealer gel. (Then repeat the curing process.)

BEHIND THE SCENES: This is thin viscosity clear or colored gel that protects the enhancement from chipping or yellowing. It gives the builder gel, an inherently weaker gel, scratch- and moisture-resistance.






ACTION: Notice a tacky layer on the nail.

BEHIND THE SCENES: This is uncured gel. Oxygen inhibited the top layer from curing. (If we were on a planet that was nitrogen only, we wouldn’t have this problem and the gel would fully cure.) The bottom layers of gel aren’t exposed to the oxygen at the surface, which is why that’s not a problem there. (If this layer seems thicker than usual, then you are having a problem with curing at the lower levels, which likely means your light needs new bulbs.)



ACTION: Wipe the tacky layer with the manufacturer’s designated product.

BEHIND THE SCENES: It would be possible to use other cleaning materials, but the most effective are isopropanol, methyl ethyl ketone, acetone, ethyl acetate, n-propyl acetate or a blend of these solvents.  Water is not recommended because it won’t remove the uncured gel.  Be careful not to touch this uncured gel (i.e., don’t file it off, then rest your arm in the filings).   A plastic-backed pad is ideal, as  the uncured gel can potentially soak through plain cotton.

Special thanks to the following industry scientists for providing background information for this article: Doug Schoon, author, Nail Structure and Product Chemistry ( and Jim McConnell, president, Light Elegance (  

Want to know the science behind other products? Learn about polish ingredients at and the chemistry of acrylics at

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