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Knot treatment in wood painting

Short answer

Clean the knot, remove oozing resin, and apply two coats of shellac knotting or aluminium paint to seal it. Fill any depression with putty, sand smooth, then proceed with priming and painting.

How is knot treated for painting in wood works?

Knots in timber contain resin that oozes out through the paint and spoils the finish, so they must be treated (knotting) before painting.

  1. Clean the knot with sand paper and remove loose fibres and dirt.
  2. If resin is oozing out, scrape it off or burn it with a hot iron or blow lamp, and clean it again.
  3. Apply two coats of knotting: a solution of shellac in methylated spirit (or a coat of red lead or aluminium paint) over the knot and slightly beyond it, allowing it to dry between coats.
  4. Fill any hole with putty, sand smooth, then apply the primer and paint coats.

This seals the resin and prevents the knot from showing through the paint.

✓ Answer checked by Claude Opus 5.5 (high effort)

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