How to Prepare Woodwork for Paint
The secret of a good painted or varnished finish on wood is to spend time preparing the surface before you get down to the job itself. Wood must be sound and blemish-free, and any knots, common in softwoods such as pine, will need treating with a knotting solution (shellac) to prevent resin from seeping out and ruining the finish.
Pre-painted wood
If the existing paintwork is sound, there is no need to strip it back to bare wood. Simply wash the area carefully with a sugar soap (all-purpose cleaner) and water solution, lightly sand with abrasive paper, then remove any traces of dust before painting. Where there are patches of bare wood, apply primer, then undercoat as normal. Finally, you should sand lightly before painting on the top coat.
However, if the paint or varnish is chipped or blistered, you will have to remove it. Use a scraper to get rid of loose fragments; a triangular scraper, known as a shavehook, is handy for getting into tight corners and mouldings. For stripping large areas of wood, the choice is between a chemical stripper and a hot-air gun. If you opt for the former, you will need to neutralize the surface, as recommended by the manufacturer, once the old paint has been removed. A hot-air gun will make light work of removing large areas of paint, but take care around windows, as the heat may damage the glass.
If you plan to paint over a faded woodstain, you will not be able to remove the old finish. In this case, simply sand the area, remove the surface dust, then apply one or two coats of an aluminium-based primer before over-painting.
Bare wood
There is a three-step sequence to painting bare wood:
– First, coat with a primer and lightly sand when dry. Wipe the surface with a lint-free cloth and white spirit (paint thinner).
– Apply an undercoat as specified by the manufacturer of the top coat you’ll be using, and sand again. Remove any traces of dust with a lint-free cloth moistened with white spirit.
– Paint on the top coat. Normally, this will be a gloss finish, as it is hardwearing and easy to maintain. When varnishing bare wood, sand away any rough edges, wipe off the dust, then apply the finish.
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