Expert tips on surface preparation before painting

Preparation is the key to a quality painting job. If you're meticulous now, you'll be able to sit back and enjoy a perfect finish once your job's done. Here're some expert tips.

  • Whether the paint that's already on it is water-based or oil-based, wood trim usually looks best if the built-up paint is removed before you apply fresh paint. But, if the trim already has five or fewer coats of an oil-based paint, then you could probably get away with adding a fresh coat or two on top. This short cut won't work for water-based paint, though. So if you're planning on repainting trim that's been painted with water-based paint, then you'll have to sand or strip the old paint away before applying a new coat.
  • Chemical strippers come in many forms, but the best choice for vertical surfaces is a gel-type stripper that will cling to the surface. This way the chemical will have a longer time to work at stripping away the paint. If you don't want to work with a gel-type paint stripper, you could try using some wallpaper paste to thicken a standard stripper.
  • The golden rule when stripping paint with a blow torch or heat gun is to keep the tool moving. Too much heat on one spot will burn and char the paint rather than soften it. If you linger with your torch or gun, you also risk scorching the wood under the paint.
  • After you've stripped a wooden surface be sure to seal up any knots. If unsealed, the resin from knots can seep through fresh paint. As a rule when repainting wood, it's always a good idea to apply wood primer to the whole surface first.
  • To contain blobs of paint and stripper as you clean your putty knife, use tin snips or a hacksaw to cut a vertical slot in the side of a large coffee can. The slot should be just a little deeper than the thickness of the putty knife's blade, and just a little wider than its width. To clean, slide the putty knife down the slot, then pull it towards you, scraping the blade as you go. The residue will drop neatly into the can.
  • To remove a rough section of built-up paint, try wrapping some leftover window screen (make sure that it's metal, not fibreglass) around a piece of scrap wood. Use the wrapped wood like it's a sanding block and it will remove paint quickly without damaging the surface.
  • One way to preserve the definition of wooden mouldings while removing layers of old paint, is to work with a shave hook or homemade tools instead of sanding blocks. A small metal washer held between locking pliers, for example, is ideal for scraping concave sections. To finish this sort of finely detailed stripping job, wrap fine abrasive paper around a piece of wooden dowel and sand lightly up and down the grooves. You could also use an abrasive sponge block.
Expert tips on surface preparation before painting

Keeping safe around lead-based paint

  • Any pre-1960s paintwork is likely to contain lead — but thankfully you can buy an inexpensive test kit from a DIY store to check any paint job that you're thinking of working on.
  • If you do need to strip lead-based paint, there are some precautions that you must follow:
  • Never use a blow torch, heat gun or sand paper, all of which produce lead-rich fumes and dust that are dangerous to inhale or ingest in any way.
  • Instead, wear gloves and a dust mask for the stripping job and use a chemical paint stripper.
  • Put any waste from your lead-based paint stripping job in a sealed bag immediately.

Keeping these expert tips in mind when you prepare a surface you want to repaint will help you do it smoothly the first time.

The material on this website is provided for entertainment, informational and educational purposes only and should never act as a substitute to the advice of an applicable professional. Use of this website is subject to our terms of use and privacy policy.
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