Why is it necessary to use wax and grease remover before sanding?

Using wax and grease remover before sanding is crucial to prevent contamination of the surface. Contaminants like wax, grease, oil, and dirt can interfere with the adhesion of primer or paint to the substrate. If these substances are not removed prior to sanding, they can create a barrier that prevents coatings from properly bonding, leading to future issues such as peeling, flaking, or bubbling paint.

This cleaning step ensures that the surface is as clean and smooth as possible, allowing for a more effective sanding process. A contamination-free surface enables the sandpaper to effectively abrade the substrate, which is necessary for creating a rough texture that promotes better adhesion of subsequent layers.