Sanding and polishing can turn a wavy, dusty or bubbled epoxy surface into a clear, glossy finish. It’s also how you prepare cured epoxy for another coat.
1. Wait for the right cure
Sanding too soon gums up the paper and can tear the surface. Follow the product’s cure time for sanding. That’s often longer for thick pours and in cool shops. If the surface is waxy, wash off any amine blush with water and a scrub pad before sanding (see amine blush).
2. Level
Start with the finest grit that will remove the defects. That’s often in the 120-220 range for drips, ridges or dust nibs. A random-orbit sander on a flat surface keeps things level. Hand-sanding with a hard block works for edges.
3. Refine
Work up through the grits without skipping too far, for example 320, 400, 600 and beyond. Each grit should remove the scratches from the one before. Wipe or vacuum between grits and look at the surface under a raking light.
4. Wet sand the fine grits
From the finer grits up, wet sanding with waterproof paper keeps the paper from clogging and reduces dust. The surface will look evenly hazy, which is normal.
5. Polish
Finish with a polishing compound on a foam pad, then a finer polish, much like automotive paint correction. Work small sections and keep the pad moving to avoid heat build-up.
Or recoat instead
For a tabletop, it’s often faster to sand evenly to a mid grit, clean the surface well, and pour a final flood coat. A well-poured coat comes out glossy on its own.
Safety
Sanding dust from epoxy that isn’t fully cured can irritate skin and lungs and can cause sensitization. Wear a dust mask or respirator and eye protection, and use dust extraction. See epoxy safety basics.
Product guidance: WEST SYSTEM instruction manuals. Related: preventing bubbles