With any decorating job, adequate preparation is 90 per cent of the battle. Practically all faults and failures which are blamed on materials can be traced back to the fact that the surface upon which the material was placed had been poorly prepared.
Before you start work, cover the floor and any furniture still in the room with dust-sheets or a thick covering of newspapers.
You can quite safely paper over emulsion paint on a wall, but it must be washed down first using warm water with a little detergent in it to remove any grease or dirt. It is also possible to put new paper on top of old, but here the new paste may weaken the adhesive power of the old, resulting in bubbles or even the whole lot coming away.
But whether you decide to take a chance about this or not, you must remove any shelves which are screwed to the wall, wall light fittings, hooks and so on, and insert matchsticks into the screw holes before papering. When papering over the matchsticks, they will poke through the paper and you will not spend hours trying to find where the holes were. If you do disconnect light fittings, first turn off the current at the main and then bind the ends of each wire separately with insulating tape. If you have to switch the current on again, perhaps because someone is cooking the lunch in another part of the house, make absolutely sure that it is off once more before you start working in the area where the lights are. Wet paste is a good conductor of electricity.
Stripping off old paper
All in all it is much better to strip off the old paper, and you can buy special strippers for this. However, all but the most stubborn of papers can be removed relatively easily simply by soaking them well with warm water, applied with a sponge over a fairly small area at a time, and then working the paper from the wall with a scraper. Quite large pieces may simply pull away without any great effort on your part. Take care not to dig into the plaster with the scraper or you will have a repair job to do later.
Heavy papers will take rather more soaking than others to come free, and vinyl ones will need their surface scratched with a wire brush or scored with a scraper, so that the water can penetrate through the plastic coating to the paste below. With some special vinyls the surface is designed to peel away, leaving the paper backing, which you can use as a base for your new paper.
Filling in cracks in walls
When the walls are down to bare plaster, examine them carefully. If they are sound and quite unmarked you will be extremely lucky, but it is more than likely that there will be cracks or small pieces of plaster chipped out here and there. If these cracks are ignored it is unlikely that the house will fall down, but they may get worse in time and they could quite easily show through the paper.
Small cracks and chips can be filled with a quick-drying, cellulose preparation like Polyfilla, or a plaster-like material such as Keene’s cement. First, with a sharp, pointed knife, widen the crack just enough so that you can undercut the edges. This will hold the filler firmly in place when it hardens. Press the filler into the crack with a filling knife, leaving it a little proud of the wall surface. It will quickly dry, and when it has done so, rub it smooth and level with the wall with fine sandpaper. Any rough patches in the plaster should also be sanded smooth.
If you have done much sanding, leaving a porous surface, it is a good idea to give the whole wall a coat of wallpaper paste, thinned to a liquid consistency with water. This is called sizing and will seal the pores to give a good working surface.
Brush down and wash the ceiling first of all. It may well have lining paper on it, possibly used to disguise a poor surface, for ceilings are subject to cracking more than solid walls. If the lining paper is adhering firmly, do not remove it, or you may find that you have major repair work to do. If, on the other hand, the ceiling is bare plaster, repair any small cracks just as you would on a wall, and size it with wallpaper paste.
Ceilings are often subject to a certain amount of movement, caused possibly by settlement of the house, or even by the shifting of heavy furniture in the room above. The repair of a bad crack can be given added strength as follows.
Fill it with either a cellulose or plaster-like filler, sand down when dry, and then paste a piece of lining paper over it so that it covers the crack and about 25 mm of the ceiling all round it. There should be enough of the paper so that the edges, which should not be pasted, hang down all round. When the paper has dried and is firmly stuck, tear the edges away, pulling in towards the centre all the time, so that you are left with a feathered edge. Give this a thin coat of filler and lightly sand it smooth when it is dry. The repair will hardly be visible, but you can give it a coat of emulsion, which will blend it into the ceiling even more effectively.
The first thing to do before tackling any painting job is to assess just what needs doing. If old paintwork is in good condition, it is unnecessary to strip it off. Odd patches of flaking may be found round door panels and window frames, but these can be sanded smooth and any cracks and crannies filled with a filler. Many modern paints take quite happily over old gloss paint without your having to do anything to the surface except wash it down. If this is so with the paint you choose, it should say so on the tin, but if in doubt a light sanding over the whole surface will give a key for the new paint to stick to. If you are painting over a very dark colour, an undercoat is advisable.
Should the old paint be in such a bad condition that it must be removed, the two easiest methods are burning it off or using a chemical stripper. The latter will be more costly over a large area.
A modern gas blow-torch makes burning off much simpler than trying to cope with the temperamental old-type blowlamps. The flame will soften the paint so that it is easily worked off with a scraper, but keep the torch moving so that you do not burn the wood.
There will be some areas where you cannot use a torch. If used on windows, the heat would be likely to crack the panes, so a chemical stripper is best here. The properties of strippers vary from make to make, so read the instructions very carefully before you start work. All should be applied with an old brush, which will not be any use for painting with afterwards. In general it can be said that strippers either soften the paint much as a blow-torch does, so that you use a scraper with them as before, or else at least partially dissolve it. Very careful washing down afterwards in line with the manufac-turerers instructions is needed so that no stripper is left in odd corners. Wear rubber gloves when working with strippers.
Stripping paint can also be done by sanding, but except for very small areas, if this is done by hand it is a most tedious job. Mechanical sanders are much quicker, but they do create an incredible amount of dust.
After stripping, rub the surface down with M2 grade glasspaper, following the grain. Cracks should be filled with a proprietary wood filler, sanding smooth again afterwards.
New, unpainted wood should, after sanding, have the knots sealed with a knotting varnish, which will stop any resin seeping from them, and then a primer coat applied before the undercoat. Aluminium primer both seals knots and primes at the same time.