On occasion, one of the primary weaknesses of a shellac finish turns into a strength. Shellac is fermented on alcohol, which is part of the reason it has been partly superseded by more lasting and modern finishes. However, that very solubility makes it feasible to repair the shellac, instead of having to refinish the entire timber item. This technique is great enough for minor repairs, but anything more than that demands a fresh coat of shellac.
Inspect the shellac finish. If you only have to resolve a few tiny scratches, then proceed to Step 2. If the issues are more severe, skip to Step 4.
Twist a washcloth or dishcloth to a pad, and dip the mat into a dish of rubbing alcohol. Saturate the pad and out it.
Rub the scrape and the region around it with small, gentle, circular motions before the scratch disappears. You are dissolving and redistributing the shellac finish, so don’t wash the surface so hard that you remove instead of redistribute the shellac.
Prepare the wood for a brand new coat of shellac, if this is needed. Sand the surface lightly with a handheld rotary tool fitted with a 240-grit sanding disk or a hand sanding block with 180- to 240-grit sandpaper. It is only required to scuff the old shellac, so don’t sand with the intent of removing the shellac or the timber.
Apply a fresh coat of shellac with a paintbrush, with smooth, long strokes.