STRIPPING WOOD
Wood has a natural beauty, but it’s often a beauty concealed by layers and layers of paint. Doors, window frames, even skirting boards and architraves can all become attractive features in themselves when stripped back to reveal the wood. Even if you prefer to repaint, using the right techniques to strip off the old will give the best possible surface on which to work.Most professional Painters and Decorators prefer to strip the paint off before painting woodworks.
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. Either way, once wood has been stripped back to its natural state, it then has to be sealed again – to protect it from moisture which can cause cracking, warping and ultimately decay. Both varnishes and paints act as sealants, giving a durable finish. But which one you choose might depend on the wood itself – and you won’t know what that’s like until you’ve stripped it.
If you’re unsure of its quality, it’s advisable to strip a test area first. Some of the timber 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 ‘knotting’ – a special liquid sealer – to make the knots tight and prevent them ‘bleeding’, filling cracks and splits to give a flush surface) and then paint to seal.
If you are set on having the wood on show and don’t want to paint it – because it wouldn’t fit in with a colour scheme or make the feature you want – you can give it a better appearance and extra protection with stain or coloured varnish.
Stripping with abrasives
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 off wood. On large areas such as floors it is best to use a purpose-made power sander which you can hire. A drill with a sanding attachment, however, is useful for getting small areas smooth after 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 round 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 mouldings they smooth well and are useful for rubbing down between coats. These sanders are rectangular and should be moved over the surface in line with the grain.
Make sure you choose the right type of sander, depending on the work in hand. For sanding by hand – hard work, but much better for finishing – there are many grades of glasspaper from the coarse to the very fine. On flat surfaces it’s best to wrap the paper round a small block of wood. As an alternative to glasspaper, there’s also steel wool, which is most useful when you’re trying to smooth down an intricate moulding.
Always sand backwards 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. Renew the sandpaper frequently as the paint will clog the surface, although a useful tip is to try cleaning clogged paper with a wire brush. It’ll work once or twice, but after that the abrasive surface is usually lost.
Alternatively pull the sheet backwards and forwards, abrasive side uppermost, over a table edge to dislodge paint particles. A useful tool for cleaning paint from corners and mouldings 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.
Heat stripping
Heat stripping is the quickest way to remove paint or varnish, but it needs a lot of expertise if you are to avoid charring the wood. So it is best reserved for stripping out of doors where a less-than-perfect surface will be less noticeable. A gas blow-torch or an electric blow torch is used along with metal scrapers to lift the finish off the wood while it’s still warm. Blowtorches with gas canister attachments are light to use and a flame spreader nozzle makes the job easier (it can be bought separately). Where there’s no glass, it’s a two-handed operation. Light the blow-torch and hold it a little way from the surface.
Move it back and forth, going nearer and withdrawing, till the paint starts to wrinkle and blister. Now begin to scrape – be careful where you point the flame at this stage or you may damage other surfaces. As soon as the paint is hard to move return the flame to the area. Wear gloves to save your hands from being burnt by the falling paint, and cover areas below where you are working with a sheet of non-flammable material to catch the scrapings. In awkward areas, especially overhead, you should wear protective goggles for safety’s sake.
Chemical stripping
Chemical strippers are probably the easiest way to strip wood. Available in liquid, gel and paste forms, their methods of application and removal vary, so always remember to read the manufacturer’s instructions before you begin. Though all of them will remove paint and varnish, if you are dealing with a large area of wood they can work out to be very expensive – they’re also very messy. Liquid and gel strippers, decanted if necessary into a more convenient-sized container (read the instructions as to whether it can be heavy gauge plastic or should be glass or metal), are stippled onto the surface with a brush and left till the paint bubbles work through only 1 layer of paint at a time so several applications can be necessary.
If stripping a chair or table, stand the legs in old paint cans or jam jars so that any stripper which runs down the legs can be recycled. Artists brushes rather than paint brushes are useful when applying these strippers to mouldings or beading in windows and No 2 steel wool is useful for removing it. After liquids or gels have been used, the surface must be cleaned down with white spirit or water (it depends on the stripper used) to remove any trace of chemical and must be left till completely dry before any stain or seal is applied.
Pastes are mostly water soluble and manufacturers stress important conditions for using them safely (eg, not in direct sun, in well ventilated rooms, the wearing of protective gloves, etc). Bought in tubs ready-mixed or in powder form to be made up. they are spread in thick (3-6mm) layers over the wood which must then be covered with strips of polythene (good way of using up plastic carrier bags) or a special ‘blanket’ (supplied with the tub) which adheres – when you press it – to the paste. They have to be left for between 2 and 8 hours after which the paste can be scrubbed off (with a firm brush) or washed down.
Frequent changes of water are needed; follow manufacturer’s advice about additives (eg, vinegar). Pastes are particularly effective with extraordinarily stubborn paint or varnish in very awkward places (eg. windows, bannisters etc); or where using a scraper might damage old wood. Some pastes are unsuitable for certain types of wood and can stain it – so read instructions carefully. Washing down should not be done, for example, with valuable furniture for this can raise the grain of the wood.
Bleaching
If the wood is discoloured once stripped (either from the stripper used or from some other source) you can try and achieve an overall colour with bleach – the household type, used diluted 1:3 with water to begin with and more concentrated if necessary, or better still a proprietary wood bleach. Clean the surface of the stripped wood with paint thinner and steel wool and leave for 15 minutes to dry. Cover areas you don’t want bleached with polythene, then brush bleach on generously. Work it into the wood with the grain using medium steel wool. Leave for 2-4 minutes, then wipe off with rags. Leave to dry (up to 5 hours) before sanding after which you can finish the surface as desired.