What effect does high humidity have during coating application?

High humidity during coating application primarily affects the evaporation rate of solvents in the coating material. When humidity levels are high, the air contains a significant amount of moisture, which slows down the evaporation process of the solvents present in the coating. This slower evaporation can lead to problems such as longer drying times, which may result in issues like sagging, running, or blooming (cloudiness). Additionally, the slower curing process can affect the film's final properties, including adhesion and durability.

The other options do not accurately describe the effect of high humidity during coating application. While high humidity can influence certain characteristics of coatings, it does not inherently increase gloss or enhance color retention. Rather, these characteristics can be compromised due to the slower drying times and potential film integrity issues caused by moisture. Therefore, understanding the impact of humidity on solvent evaporation is essential for achieving optimal application conditions and ensuring a successful coating job.