Expert tips on surface preparation before painting

Remove accumulated paint

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.

Strippers

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.

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.