What is sanding scratch swelling?

• A. Visible scratches that appear after painting
• B. A swelling of sanding equipment
• C. An early stage of priming
• D. A polish defect

Answer: (A)

Sanding scratch swelling describes how sanding marks show up after the surface has been painted. When you sand a surface to prep it, you create fine scratches. If those scratches aren’t fully removed or filled by the subsequent coats, light reflects differently along the scratch lines, making them appear as raised or swollen areas once the paint cures. In practice, you’ll see visible scratches in the finished finish even though they were present only during prep. The way to prevent it is to properly refine the prep: use progressively finer sanding grits, ensure all sanding scratches are removed, clean the surface well, and apply coatings with enough film build to level over any remaining marks. It’s not about swelling of equipment, early priming, or polish defects.