How to paint over polyurethane woodwork

Written by beverley gee | 13/05/2017
How to paint over polyurethane woodwork
You can paint over varnished wood after preparing the surface. (Wood planks as background image by Lucy Cherniak from Fotolia.com)

You can paint over a surface of polyurethane varnish if you prepare it properly. Polyurethane is typically hard, durable and glossy, and it is these qualities that make a finish vulnerable to chips and flaking. You don't have to remove all the varnish before you start painting. Preparation will pay off in the long run by providing a long-lasting finish.

Things you need

  • Clean, lint-free cloths

  • White spirit

  • Wood filler

  • Protective face mask

  • Fine-grade sandpaper

  • Liquid sandpaper (optional)

  • Paintbrushes

  • Oil-based primer

  • Oil-based topcoat

Clean the surface with a cloth dampened with white spirit. Fill chips, holes or other damage with wood filler.

Sand the surface with fine-grade sandpaper. Wear a protective face mask; dust from polyurethane varnish is toxic. Roughen the surface enough so the paint will adhere to it. Remove dust with a clean cloth and white spirit. Alternatively, use a liquid sandpaper that will dissolve the gloss surface of the varnish. Follow the manufacturer's directions.

Apply a coat of primer to the wood. Don't skip this step; primer provides the proper surface to which a topcoat will adhere; it also disguises areas of filler. Allow to dry overnight.

Paint on the first application of a topcoat. Let it dry overnight, then lightly sand and wipe the surface with a clean cloth and white spirit.

Apply the second coat of topcoat. Allow the surface to cure for 72 hours before handling it or placing objects upon it.

Tips

  • Avoid "one-coat" paints; they are expensive and do not provide a long-lasting finish. If you do inadvertently sand back to the wood, you need to make sure that your primer is capable of stain-blocking, as natural wood can bleed resins that will force their way to the surface and spoil the painted finish.

Warnings

  • Make sure your work area is well-ventilated. Dispose of used cloths carefully, as they are flammable. Do not use latex or water-based paint over polyurethane; the finish may crackle and it would be difficult to remove the paint.

Tips and Warnings

  • Avoid "one-coat" paints; they are expensive and do not provide a long-lasting finish.
  • If you do inadvertently sand back to the wood, you need to make sure that your primer is capable of stain-blocking, as natural wood can bleed resins that will force their way to the surface and spoil the painted finish.
  • Make sure your work area is well-ventilated.
  • Dispose of used cloths carefully, as they are flammable.
  • Do not use latex or water-based paint over polyurethane; the finish may crackle and it would be difficult to remove the paint.

Things you need

  • Clean, lint-free cloths
  • White spirit
  • Wood filler
  • Protective face mask
  • Fine-grade sandpaper
  • Liquid sandpaper (optional)
  • Paintbrushes
  • Oil-based primer
  • Oil-based topcoat

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