What is the difference between lightfastness and weatherfastness of pigments?

Many coatings that use pigments (or dyes) as colorants need to maintain a stable inherent color during application.

Many coatings that use pigments (or dyes) as colorants need to maintain the stability of their inherent colors in their applications. We define the lightfastness of pigments as the quality and technical indicators of the pigment's resistance to sunlight. Among the components of sunlight, the most destructive part of the lightfastness of pigments is ultraviolet (UV). When we discuss the lightfastness of pigments, we only evaluate the quality and technical indicators of the pigment's tolerance to the light environment in the external environment.

In fact, it is difficult for us to make an accurate definition of weather conditions. From a certain perspective, the lightfastness of pigments excluding other external environmental factors may help us give a meaningful and reproducible objective evaluation of the field stability of the coating. The weatherability index of pigments is affected by a variety of external environmental factors, including sunlight, high-energy ultraviolet radiation, temperature, humidity and erosion by various impurities in the atmosphere. The weatherability index of pigments can be measured through outdoor exposure experiments or indoors through artificial atmospheric aging equipment to simulate the field environment.