Hair that has the largest diameter and usually requires more processing time is:

Coarse hair is characterized by its larger diameter compared to fine and medium hair types. Because of its density and structure, it typically requires more processing time when subjected to chemical treatments such as coloring or perming. The thickness of coarse hair means that it can be more resistant to chemical penetration, which necessitates a longer exposure time to achieve the desired results. This concept is essential in esthetics, as different hair types require varied approaches to treatments in order to ensure effective outcomes while maintaining hair health. Understanding the differences in hair texture and structure is crucial for estheticians when selecting products and devising treatment plans.