It’s time to craft the final shape of your part and prepare the surface for clear coat. In this post we’ll cover best-practices for preparing your carbon fiber part for a gloss or matte clear coat. Correctly preparing your part is critical for achieving a high-quality finished part.
Begin by using coarse (40) and fine (80) perma-grit tools to shape any areas with excess material, such as sharp interior corners, tight radiuses and chamfered edges. Avoid scuffing the surface of the part if possible. For hard to reach spots, create a custom shaped tool by wrapping sandpaper around an appropriately shaped object, like a popsicle stick. Use 180 grit paper to smooth edges and remove any loose fibers. Next, work up through the finer grits in 1.5-2x increments to remove any scratches that would be visible through the clear-coat. Keep in mind that 180 grit scratches are the largest that can be successfully covered by clear coat.
The surface needs to be leveled of any defects and uniformly scuffed so that the clear coat will adhere. Use 180 grit sandpaper to level and scuff. Be careful not to sand through the thin layer of resin covering the part and into the carbon weave. This will cause unsightly distortion of the weave pattern, called ‘burn through’. Once you’ve scuffed the entire part, rinse with soap and water and allow to fully dry. Visually confirm that the scuffing is uniform before moving to the next step.