The addition of which agent enhances the flow of the coating after application, eliminating defects like brush marks?

The addition of flow agents enhances the flow of the coating after application by improving its leveling properties. When a coating is applied, it can sometimes dry with visible brush marks or uneven surfaces due to the way the liquid spreads across the substrate. Flow agents work by reducing the surface tension of the coating, allowing it to spread more evenly and fill in imperfections, resulting in a smoother finish. This is particularly important in painting applications where aesthetics and uniformity are critical.

In contrast, while plasticizers provide flexibility and improve adhesion, they do not primarily affect the flow characteristics. Driers, on the other hand, are designed to speed up the drying process but do not influence the flow behavior of the paint itself. Fungicides are used to prevent fungal growth in coatings but have no impact on flow or leveling properties. Therefore, flow agents are the ideal choice for addressing surface defects like brush marks.