Preparing new wood
New wood requires relatively little preparation before paint, stain or varnish is applied. It must be clean and dust-free, however, as any debris will spoil the finish. Rough areas should be sanded and the dust wiped off.
Before new wood can be painted, the knots must be sealed with knotting solution to prevent them from seeping resin, which can stain the paint even after it has dried. It is a good idea to remove some of the resin before sealing the knots. To do this, apply heat using a hot-air gun to encourage them to weep, then wipe away the resin with a cloth soaked in white spirit. Apply the knotting solution with a small brush and wipe clean with methylated spirits. Two coats are ideal (it is quick to apply as it dries very fast), but one coat will suffice.
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Preparing painted surfaces
Use a sandpaper block to smooth surfaces and provide a key for painting. Work along the grain of the wood.
Preparing previously finished wood for painting or varnishing
If the existing finish is painted and in good condition, and door panel mouldings, architraves or glazing bars have clear edges and are not clogged with paint or varnish, wash the surface thoroughly with sugar soap or liquid sander ( 206 207). Rinse well and dry. If you are not using liquid sander, lightly sand the surface with sandpaper or wet-and-dry abrasive paper wrapped around a cork block to create a key for the new paint to grip, and to soften the edges of any chips in the finish prior to touching them up with primer/ undercoat. Bad chips may need filling and re-sanding. Always fill after the first coat of primer or primer/undercoat has been applied, as this helps the filler to grip.
If the existing finish is oiled or waxed, the wood will need thorough washing down before painting ( 206 207).
Paint or varnish in poor condition will have to be completely stripped and the woodwork freshly primed and painted. Dry, flaky paint can be brushed off with a wire brush or dislodged with a scraper. The surface must then be sanded, with extra attention being paid to any stubborn patches of old paint. For large areas use an electric orbital sanding machine.
Hot air gun Thick, gungy paint that is clogging mouldings can be removed using a hot-air gun or by applying a chemical paint remover. If you use a hot-air gun, keep it moving along the wood to avoid scorching
2 If the paint is hard to shift, or if large areas must be removed, an electrical orbital sander may be helpful.