Decorating Preparation, Fixing Problems and Common Faults
Some of the faults that mar paintwork are avoidable if you think ahead when decorating. Prevention is easier than cure, but when these faults — or others which cannot be foreseen — do occur, they can usually be put right.
Blisters and bubbles
Usually caused by moisture or resin trapped in wood beneath the paint surface.
Cut out the blistered paint with a knife, and clean out under the blister. Then knot or prime, fill with stopping, and sand the area so that there is no ‘step’ between it and the surrounding surface.
Allow the sanded surface to dry out properly. Then prime all bare and filled areas before repainting.
This is a common fault in plaster walls.
Fill hair-line cracks with Alabastine, wider cracks with cellulose, such as Polyfilla, and large ones with plaster.
Rake out all loose material from the crack and, if necessary, cut it back to provide a firm edge. Dust down with an old brush.
Mix theto a fairly stiff consistency, dampen the crack and press the filler home. Smooth the surface down with your filling knife.
When the filler is dry, sand it back to the level of the surrounding surface with medium glass-paper. Use Alabastine to bring up any small dents.
Fill wide cracks in two or three stages, allowing each layer time to dry. Plaster and Polyfilla tend to dry slightly harder than the surrounding surface.
A good technique is to fill cracks nearly to the top with these materials and give a finish with Alabastine, which can be cleaned off to the level of the wall more easily.
The result of applying one type of paint over another, entirely different, type. The original paint expands and contracts at a different rate from the new paint and so causes it to crack.
If the fault is extensive, the entire surface must be stripped down and repainted. You may be able to remedy small areas of crazing by rubbing down with wet-or-dry paper and putting on a new top coat.
Chips and dents
To repair deep chips, remove any loose paint, prime any bare patches and fill with stopping or Polyfilla.
Sand the filler down to the level of the surrounding surface when it is dry. Give the filler a sealing of primer before repainting.
A white deposit on plaster, concrete, brick and stone caused by salts working through to the surface.
Strip the paint off the affected area and allow to dry; then cover the surface with an alkali-resistant primer and redecorate.
Efflorescence is usually found in new houses, but it can continue for years if moisture continues to permeate a wall.
If it lasts for more than 18 months after a house has been completed, investigate the cause of the dampness and rectify it before attempting to cure the efflorescence.
Some of the more common causes are: inadequate surface preparation before painting, moisture behind the paint film, efflorescence and the use of poor distemper in steamy conditions.
If the damage is extensive the surface must be stripped and carefully prepared before it is repainted. Make sure you use the correct primer.
Small areas of flaking may be treated in the same way as blisters.
Usually found in kitchens and bathrooms where the above-average temperature and humidity favour its growth.
Mould usually takes the form of small red, brown or black patches on the surface of the paint. It often occurs around steel window-frames in the putty line; but do not mistake the effects of rusting nail orheads for mould.
Treat with a fungicidal wash to kill the growth, and repaint if necessary.
Large areas of mould on walls which show signs of the plaster breaking down indicate damp penetration through the wall itself.
If mould is being caused by condensation, improve ventilation by fitting an extractor fan.
Bittiness. Small pimples on the surface of new paintwork, usually caused by dust.
Allow the paint to harden, then rub the surface down with fine 400 grade wet-or-dry paper. Apply a fresh finishing coat.
Curtain, sags and runs. These unsightly marks can be due to a number of causes. The paint may not have been spread in an even film, or too much paint may have been put on a surface.
Allow the paint to harden properly, then smooth down the fault with fine wet-or-dry paper. Follow this with another finishing coat.
Grinning. When an old coat of paint shows through the new one.
Rub the surface down and apply an extra finishing coat — or more if they are needed.
Lifting. This happens when a new coat of paint pulls the old one away from the surface. It can be caused by applying the finishing coat before the undercoat is dry.
When the surface is thoroughly hardened, rub the affected area down with fine wet-or-dry paper and apply an undercoat before putting on another top coat.
Slow drying. Sometimes due to painting in cold weather, in which case the only answer is to wait; in time the paint will dry.
It may also be the result of painting over wax, grease or wet primer. If so, strip off the new paint, clean off, and repaint.
Uneven gloss. This fault usually indicates that the surface was not properly primed; prime the affected area and repaint.
It can also be caused by damp or frost affecting the paint while drying, in which case put on a second coat of gloss in more favourable weather.