What type of application does not require sanding?

A wet on wet application does not require sanding primarily because it involves applying a new coat of paint or clear coat over a previously applied wet coat of the same material. This technique allows the solvents in the wet coat to blend and chemically bond with the new layer, creating a strong adhesion without the need for abrasion. The surface is still tacky, which facilitates this bonding.

In contrast, the other application types generally necessitate sanding to promote adhesion. A dry-to-dry application involves applying paint to a fully cured layer, which typically requires sanding to ensure that the new layer adheres properly to the existing surface. Similarly, spot repair applications often need sanding to create a smooth transition between the repaired area and the surrounding paint surface for effective blending. A single coat application may also require sanding if it is being applied over an old, cured surface to enhance adhesion. Therefore, wet on wet is unique in that it allows for a seamless application without the sanded preparation.