Since putty is absorbent, a coat of paint applied directly over it would lead to the paint being absorbed unevenly, leading to patches. A primer layer on top of the putty is a must. It ensures that the paint adhesion to the surface is proper, enhances the durability of paint, and imparts extra safety to the surface being painted. It takes away the unevenness caused by putty and the final paint comes out perfect. If suitably applied, primers will enhance the life of the paint and also improve its appearance.