Stripping Wood – Part of Painting Preparation
Stripping wood of old paint or layers of ancient varnish isn’t the easiest of jobs. It’s usually only done because you’re after a natural finish, or because the painted surface has degenerated to such an extent that further coats of paint simply can’t produce a smooth finish.
Some of the wood used in houses is of a grade that was never intended for a clear finish – large ugly knots, cracks, splits or even an unattractive grain are some of the signs. In cases like this, it is probably better to treat the problems (eg, applying a special liquid sealer to make the knots tight and prevent them from ‘bleeding’; filing cracks and splits to give a flu surface) and then paint to seal.
If you are set on having the wood on the show and don’t want to paint it – because it wouldn’t fit in with a color scheme or make the feature you want – you can give it a better appearance and extra protection with stain or colored varnish.
Stripping with Abrasives
Basically, stripping wood of old paint with abrasives entails using either sandpaper or scraping tools.
For dry stripping, there are several different kinds of powered sanders available, all of which use abrasive papers of some kind to strip the surface of the wood. On large areas, such as floors, it is best to use a purpose-make power sander which you can rent. A drill with a sanding attachment, however, is useful for getting small areas smooth after the paint has been removed by other methods.
One such attachment is a ‘disc sander’ and is quite tricky to use effectively without scoring the wood surface. Hold it at a slight angle to the wood and present only half the disc to the surface. Work in short bursts and keep the disc moving over the surface – if it stays too long in one place it can damage the wood.
A ‘drum sander’ attachment has a belt of abrasive paper stuck around the edge of a cylinder of foam, and if used along the grain only is rather easier to handle than a disc sander. Whichever type is chosen, a fine grade abrasive should be used for finishing stripped wood.
Orbital sanders (which are also known as finishing sanders) usually come as self-powered tools – although attachments are available for some drills. These have a much milder action and as long as the spread of wood isn’t interrupted by moldings they smooth well and are useful for rubbing down between coats. These sanders should be moved over the surface in line with the grain.
For sanding by hand – hard work, but much better for finishing – there are many grades of sandpaper from the course to the very fine. On flat surfaces, it’s best to wrap the paper round a small block of wood. As an alternative to sandpaper, there’s also steel wool, which is most useful when you’re trying to smooth down an intricate molding.
Always sand backward and forwards with the grain of the wood, not across it. Scratches across the grain will always be highlighted by a clear finish. To remove remaining bits of paint use medium grade sandpaper; for finishing, a fine grade is better.
A useful tool for cleaning paint from corners and moldings is a hand scraper with replaceable blades. These ‘hook’ scrapers are also used for smoothing and often need two hands – they slightly raise the surface of a clear run of wood, giving an attractive finish under a clear seal. Use with the grain.
Removing Paint with a Heat Gun
- Hold the heat gun about 1 inch from the paint. To prevent scorching the wood, keep the gun moving constantly. Work it back and forth over one small area – about 6 inches square – at a time.
- The paint will soften and begin to blister within seconds. Guns can reach temperatures as high as 1200oF (650oC), so you must wear heavy work gloves for protection.
- Scrape off softened paint, holding a putty knife in one hand while moving the gun over flat surfaces with the other. For complicated moldings, set gun in it stands while you scrape.
- Sand bare wood with the grain, using a fine (150-grit) paper. (First, all the paint sludge must be removed with steel wool.) Power sanding saves time on flat surfaces.
Removing Paint with Chemical Stripper
- Brush paste-type paint stripper onto the woodwork. A nontoxic stripper may not require gloves (read the label), but always wear safety goggles to protect your eyes from splashes.
- Test if the paint is soft with a putty knife (there will be no blisters or wrinkles if you use nontoxic stripper). For two or more paint layers, you may have to scrape once, reapply stripper, and scrape again. Do not let the stripper dry out on wood surfaces.
- Scrape off softened paint with a putty knife, a wall scraper, or for intricate molding, a dampened sponge and a shaving hook that can dig paint sludge out of nooks and crevices.
- Final sanding comes after all the paint has been cleaned off according to the manufacturer’s instructions. A wedge of folded sandpaper will reach recesses in the wood. Wipe the wood with a wet sponge or solvent to help neutralize the chemicals.