Decorating: Preparing Existing Paintwork
The quality of paintwork, no matter how well the final finish is applied, depends upon the care taken in preparation.
Gloss and semi-gloss
Sponge the surface down with warm water and detergent. Rinse with clean water to remove all traces of detergent.
Rub down walls with abrasive paper to provide a key for the new paint, holding the paper over a cork sanding block, or any block of wood that fits comfortably into your hand.
Waterproof (wet-or-dry) abrasive paper costs a little more than ordinary sandpaper, but it is more effective and will last a great deal longer.
For final rubbing down of woodwork, use fine sandpaper or wet-or-dry paper 280-400 grade.
Grade 400 wet-or-dry is the finest grade, and when used wet it gives a good key for subsequent coats.
Rub down small damaged areas thoroughly to remove all unsound material. Fill first and sandpaper afterwards, so that there is no ‘step’ between the damaged area and the sound paintwork. Treat bare areas as for new work.
Emulsion paint, washable distemper
Sponge down thoroughly with water and detergent, and rinse.
Scrape off any loose or flaking paint and sand down to provide a smooth surface. Prime any bare patches.
Always remove non-washable distemper before redecorating. It is made from whiting and soluble, and is easily washed off. This distemper is used mainly on ceiling paper.
Soak the surface with water two or three times, then scrape the paint and paper off with a broad stripping knife, holding a dust-pan underneath to catch the paint.
Be careful not to dig the stripping knife into the plaster.
Wash the surface down thoroughly afterwards to remove all traces of, whiting and old paper.
If the paper is stuck firmly to the wall, there may be no need to remove it.
The two main dangers in painting over paper are that the inks in the pattern may `bleed’ through the paint film, and that the water in emulsion paint may soften the wallpaperand cause blistering.
If you are satisfied that the paper is firmly stuck to the wall, simply dust it down with a soft brush and repair any tears or breaks by re-sticking them.
To test for bleeding, dab some of the paint you are going to use over a small area of the paper. If the ink does show signs of bleeding next day, either seal the paper with a primer or strip it off altogether. Soak it before stripping.
Emulsion over wallpaper
After you have applied the last coat of emulsion, the paper may bubble.
These bubbles may disappear on drying, but if not, one of two courses is open to you:
1. Cut out the bubbles and re-stick.
2. If the bubbling is very bad, strip the wall and start again
Paint over washable papers
Washable wallpaper should be sponged down with a mild detergent solution before it is painted. Rinse down after sponging.
Make sure that the paper is adhering to the wall properly and test the ink to see if it is going to bleed through the paint. Prime any worn patches.
Varnish and wood stain
Rub down thoroughly with sandpaper, to remove as much of the finish as possible.
Prime any bare wood. Seal wood stain with two coats of aluminium wood primer before painting. For a quick job, rub down to remove the shine, then prime and paint; this may well result in a finish that chips easily, so it is not suitable for skirtings.
Adhesion between paint and an old varnished surface is not good, even after rubbing down. To obtain a satisfactory surface which will not chip, it is best to strip theand treat the woodwork as for new work.
Many polishes these days contain silicone, and this must be removed completely before you paint. If any traces are left on, the paint will flow away from those parts of the surface.
Rub the surface with coarse hessian or rough cloth dipped in white spirit, turning the cloth frequently to avoid spreading the polish. Finally, clean off with sandpaper.
Sometimes these polishes are very difficult to remove, so make a test on a small, unimportant area. If the paint separates as it is applied, the surface is not clean.
Rub over with methylated spirit, then sand lightly to remove final traces of polish.
Remove with white spirit and rub down with sandpaper.
Iron and steel
An electric drill with wire brush attachment is a very useful tool for preparing these surfaces.
Rub the surface down hard with a wire brush and emery cloth to remove all rust and loose, flaking paint.
Clean down with white spirit and prime any bare patches of metal. Rub down sound paint to a smooth surface.
Rub the surface down with fine abrasive paper and clean off with white spirit. Prime any bare patches before painting.
Remove any loose surface material with abrasive paper or a wire brush. Seal with primer before painting.