What is a primary use of a photo initiator in nail services?

The primary use of a photo initiator in nail services is to enhance the curing process of UV gels. Photo initiators are compounds that absorb light and initiate a chemical reaction when exposed to ultraviolet (UV) light. This reaction causes the gel to harden or polymerize, transforming it from a liquid state to a solid form. This is essential in the application of UV gels, as proper curing ensures the durability and strength of the nail enhancement. Without photo initiators, the curing process would be inefficient, leading to weak and poorly adhered nail products.

The other options focus on aspects that do not relate to the specific role of photo initiators. Color in gel products comes from pigments or dyes, while consistency changes in nail polish are typically achieved through different formulas or additives. Preventing bacteria growth is important in nail services, but this function is generally managed through sanitation practices and preservatives, rather than through the use of photo initiators.