What type of light is used by a curing light to harden gel products?

The correct choice is the use of ultraviolet or halogen light to harden gel products. Gel nail products require a specific type of light for curing, as this light emits wavelengths that activate the photoinitiators in gel formulations. Photoinitiators are the chemicals in the gel that facilitate the polymerization process, turning the gel from a liquid state into a solid form upon exposure to the right wavelength of light.

Ultraviolet (UV) light is particularly effective for curing gel nails because it provides the necessary energy to initiate the curing process quickly and efficiently. Halogen lights can also be used in some curing units, as they provide a similar range of wavelengths effective for this purpose.

While fluorescent and incandescent lights do emit visible light, they do not emit the specific wavelengths necessary for curing gel products. LED lights are also an option for curing gels, as they too can provide the appropriate wavelengths; however, the question focuses on the more traditional curing methods, which prominently include UV and halogen light. Thus, understanding the role of ultraviolet or halogen light in curing gel products is crucial for nail technicians, as it ensures the integrity and durability of the finished service.