If a burn is superficial-that is, mars the finish but hasn’t reached the wood-first try a commercial furniture cleaner. If the mark persists, rub it with rotten stone in light oil.
Burns that have gone through the finish but not far into the wood also respond to a light touch. Gently rub the charred area with fine steel wool. Remove any remaining blackening by dabbing on straight liquid bleach with a cotton swab. To match the color of surrounding wood, try colored furniture wax or polish, artist’s oils, shoe polish, crayon or felt-tip pen, or an oil-base stain, testing first in an inconspicuous area. You can buy stain for touch-ups in felt-tip and small brush-topped containers. In matching color, start light. It’s easier to darken an area than to lighten one you’ve made too dark. Refinish to blend with the rest of the wood. Burns that go deep into wood Gently sand or scrape away the blackened wood with a single-edge razor blade or a utility knife. Then fill the area with a stick of tinted wax or shellac; the method is the same with either. Wax is easier and can be removed if you don’t like the result.
Select a color that matches the lightest grain in the wood. You’ll need a special curved knife, called a burn in knife, or a curved grapefruit knife. Heat the knife over the sootless flame of a spirit lamp or over an electric stove burner. Hold the wax or shellac stick against the heated blade and guide the melting filler into the depression in the wood. Reheat the knife as needed. Fill the hole slightly higher than the surrounding area.
When the wax has cooled, scrape off the excess with a razor blade. With shellac, scrape off any excess before it hardens, then sand when it’s hard. To match the grain, paint darker streaks across the patch with a fine tipped brush, connecting them to the grain lines of the surrounding wood. Seal a wax patch with clear polyurethane or acrylic varnish spray.