STAINING AND VARNISHING WOOD

English: Varnish on wood stairs

English: Varnish on wood stairs (Photo credit: Wikipedia)

If you want to decorate and protect the woodwork around your home without obliterating its grain pattern with paint, wood stains and varnishes offer a wide choice of finishes. Here’s how to get the best results.

W hen it comes to giving wood a clear finish, you can choose from a variety of traditional and modern materials, including oils, wax, French polish and different types of varnish. Some are suitable for exterior use, others for interior use only. The degree of skill you need to apply them varies; some are quite simple to use, whereas others, like French polish, require special techniques acquired only by patient practice. The type of wood may affect your choice of finish; for example, open-textured woods like teak, iroko and afrormosia are best treated with an oil finish – they don’t take varnishes well..You may decide to change the colour of the wood before you finish it. You can use a varnish which incorporates a colour or apply a wood stain and then coat the wood with clear varnish or another clear finish.

If you don’t wish to change the colour of the wood, but want to restore it to its natural colour – for example, where the wood has been slightly darkened by the action of a paint stripper – you can use a proprietary colour restorer.

Types of varnish and stains

Clear varnishes are like paint without the pigment. They contain a resin carried in a drying oil or spirit and it is the resin which gives a hard protective finish to wood. Traditionally, the resins used were like copal, natural and obtained from various tropical trees, but in modern varnishes they are synthetic, for example alkyd or polyurethane.

While other varnishes are available, by far the easiest to obtain and most widely used are those containing polyurethane resin. Polyurethane varnish is available in gloss, satin or matt finishes and for interior or exterior use. A non-drip variety is particularly suitable for vertical surfaces, ceilings and hard-to-get-at areas.

There are polyurethane varnishes which have added pigments and are known as coloured sealers. It’s quicker to use one of these rather than to apply a wood-stain followed by a clear finish but you won’t get the same depth of colour, and if the coloured varnish chips in use, timber of a different colour will show through.

KNOW YOUR STAINS.

– water-based stains penetrate the wood more deeply than other types and are therefore suitable for use on wood which will be subject to hard wear.

– oil stains are easier to apply without blotching than water-based ones and, since they dry quite slowly, any overlaps are less likely to show.

– spirit stains are available in a wide range of colours. They dry quickly so you have to work at speed; but this also means you can apply the varnish sooner.

– don’t use a polyurethane varnish over oil stains or a chemical reaction will spoil the finish.

CHECKING COMPATIBILITY

Always check that the stain and finish you intend using are compatible. Buying both from the same manufacturer should ensure this. If you are in any doubt, stain and varnish a small test area first.

Filler. But since stains don’t hide fillers in the same way as paint would, you may decide not to carry out such treatment and to leave the blemishes for an authentic ‘old wood’ look. If you do decide to use a filler, don’t try to smooth it flat as you apply it with the knife or you’ll risk spreading it round – it tends to show up in the nearby grain if it is rubbed in when wet.

Finally, you should make sure the surface is dust-free by wiping it with a clean, dry cloth or a fine brush. It’s a good idea, too, to wipe it with a cloth soaked in turpentine to remove any greasy fingermarks you may have left while preparing the surface.

Bleaching wood

One of the snags with staining wood is that you cannot make the surface lighter; you can only make it darker. A light-coloured stain on a darkish piece of wood just won’t work. The way round this problem is to bleach the applied if needed to get a darker finish, but wood before you start sealing it – and for this too many coats will result in the stain lying on proprietary wood bleaches are available at the surface, lengthening the time it takes tor most hardware stores. The subsequent coat of varnish to dry and Some bleaches are applied in one stage even preventing it from bonding properly to and others in two stages. The wood is the surface. With water-based types, if washed with a neutralizing agent afterwards overlaps show when the first coat dries you so the bleach doesn’t carry on working when can add about 20 per cent more water to a the finish is applied. Follow the mixed-up solution of stain and apply a manufacturer’s instructions when applying second coat over the whole surface, the bleach, particularly concerning the time brushing it out well.

You should allow for each stage of the After the stain has dried (usually about treatment. Usually, bleach is applied with a hours after application), you should rub the sponge or brush; make sure you use a white surface thoroughly with a dry cloth to remove fibre brush or the dye in the brush may come excess stain.

Out onto the wood.

Filling the grain

Staining wood It’s not necessary to fill the grain of soft- You can apply the stain with a brush or a woods, but for a good finish on open- folded lint-free rag. Aim to get the colour you grained hardwoods like oak, mahogany and want in one coat; a second coat can be walnut you will have to apply a grain filler

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To the wood surface before using varnish.

There are various proprietary fillers available in either a paste or liquid form; choose one to match the wood or stain you are using. Follow the manufacturer’s instructions for applying it; normally, you work the filler over the wood with a brush or cloth, wipe off the excess and then sand the surface lightly down with fine glasspaper.

Varnishing wood

Polyurethane varnish is easy to apply; you simply brush it on, taking care to work with the grain of the wood. Follow the manufacturer’s instructions as to the number of coats you should apply and the time allowed between each coat – at least 12 hours. You should sand down the surface lightly with flour-grade glasspaper between coats to provide a key for the next coat, and remove any dust that’s accumulated during application with a damp cloth.

As with paints, it’s advisable to stir the contents of any can of varnish that’s been stored for a while. This ensures an even distribution of the solvents so that the varnish dries evenly when it is applied. Although the varnish will be touch-dry in about 4 hours, it may take as long as 7 days before the surface reaches full hardness – so avoid standing anything on the newly-decorated surface for a week or so.

SAFETY FIRST

Varnishes, bleaches and stains can be flammable. Always work in a ventilated area away from the naked flames and don’t smoke when applying them.

PROTECT YOUR SKIN

Bleach can burn skin and clothing so you should wear rubber gloves and an apron or old clothes when applying it.

AVOID SCRATCHES

When sanding take care not to leave scratches on the wood which will be highlighted by the finish. Always work in the direction of the grain, not across it, and finish off with the finest grade of glasspaper. If you are using power tools, never press too hard.

MAKING A SANDING GLOVE

For sanding large curves, staple two ends of a sheet of glasspaper together so it forms a ‘glove’ when you put your hand through the middle.

TIP: HOW TO REMOVE STAINS

Place a damp cloth over the dent, then apply a warm iron on top of the cloth so the wood swells up and fills out the hollow.

WORKING WITH VENEERS.

– never use a bleach on a wood veneer; the bleach has to be washed off and water can loosen the veneer and cause it to swell.

– take special care when sanding a veneer; it’s easy to go right through it. Especially at the edges, and expose the timber underneath. Such damage is very difficult to repair.

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