Different Types of Wood Finish

Linseed oil

This is the cheapest of the oil finishes. It is available boiled or raw — the boiled form dries more quickly. Linseed oil takes longer than teak oil to apply but it has a greater depth of finish.

Drying can be speeded by adding a little Terebine (drier) and mixing it thoroughly with the oil. Terebine is obtainable from most ironmongers; do not confuse it with Terebene, which is used medicinally.

In common with other oil finishes, linseed oil is easy to use and needs no special preparation of the timber. Oils of all types darken the timber to give a tough, non-gloss finish without covering up the grain and texture. The finish is water-resistant and improves with age.

Resistance to damage is built up gradually over the years by additional applications of light coats of oil rubbed well in; resistance to heat and spirits is limited, but damage done by them to the finish is easily repaired.

Teak is the timber most suited to an oil finish. Afrormosia and iroka, often used as teak substitutes, also take oil well.

Rosewood, mahogany and oak can all be oiled, but light-coloured timbers, such as sycamore, ash and beech, become dirty and discoloured; softwoods, for example pine, are unsuitable for oil finishes.

Application: prepare a mixture of 1 part linseed oil and 1 part pure turpentine. Apply the mixture liberally, working it well into the timber across the grain with a brush or cloth.

Leave for an hour or two, then wipe off the surplus with a soft, dry, non-fluffy cloth. Leave for at least two days, then apply a second coat. Non-oily timbers may require up to four applications of the mixture.

Build up a sheen by hard rubbing with a soft cloth. Use a little wax polish to get a better finish.

Teak oil

This oil contains drying agents and varnishes which greatly speed up the drying process and give an improved resistance to marking, compared with pure linseed oil.

Use olive oil, which is odourless, in preference to teak oil or linseed oil, on articles which come into contact with food, such as salad bowls.

Application: apply liberally with a cloth or brush, working the oil well into the timber across the grain.

After about half an hour, wipe off the surplus oil and allow the surface to dry for at least eight hours before applying a second and much thinner coat. Do not aim to build up a coat on top of the timber; this can result only from too much oil being used.

When the second coat is dry — probably on the following day, or even later — rub down with fine steel wool (grade 00 or 000) impregnated with wax polish. Clean off with a dry, soft, non-fluffy cloth. Some non-oily timbers may require more than two coats of oil.

Destroy all cloths after use as they are self-igniting and highly inflammable.

Petroleum jelly

Vaseline can be used instead of oil for a finish but it is more difficult to apply. It is best used to give a finish to close-grained timbers, for instance teak and rosewood.

Application: rub the Vaseline well into the grain. Next day, rub off any surplus from the surface and buff up with a dry cloth. Vaseline fills the grain more than oil, but builds up a surface resistant to marking.

Wax polish

Traditionally, wax polishes were prepared from a mixture of beeswax, turpentine and carnauba wax. Modern wax polishes contain silicones and driers which cut down the work of application and give a better resistance to marking. Use a good silicone wax, not a cream or spray.

Wax polish can be applied direct to raw timber, but the finish will not be durable. It is more practical to seal the timber first with another finish, such as Ronseal, before applying the wax.

Wax finishes, like oil, have to be maintained and need more careful treatment than lacquer finishes. Their appearance, however, is pleasing, with a satin gloss that improves with age and can be quite easily repaired.

Most timbers can be successfully waxed. Oak, in particular, is well suited to waxing, but light-coloured timbers, such as sycamore and ash, tend to look dirty after a while as the wax works into the grain.

Use wax for maintaining or enhancing other finishes, such as oil or French polish.

Application: apply a light coat of the sealer by brush or cloth direct to the unfilled timber, working it well in and finishing evenly with the grain.

Allow to dry thoroughly, then sand lightly with fine abrasive paper. Some porous timbers may require two light coats, but do not apply any more than is needed to seal the surface.

Apply a heavy coat, of wax by cloth or, on flat surfaces, with a stiff brush. Work it well into the timber and finish off by stroking with the grain before leaving to harden. Leave for several hours before rubbing up with a soft brush — a shoe brush is ideal. Finally, buff with the grain with a soft cloth.

For sealed timber, apply three coats (one heavy and two light) with a lapse of several days between each.

Polyurethane lacquer

This gives an extremely tough finish, superior to cellulose and French polish in its resistance to heat, water, spirits and abrasion. It is easy to apply and maintain.

One- and two-pack varieties are available. The two-pack varieties, containing separate lacquer and catalyst, are preferable where maximum toughness is required. In the one-pack varieties, such as Ronseal, lacquer and catalyst are premixed and begin to cure on exposure to air. Do not use polyurethane lacquers on new floors.

Application: polyurethane lacquers are best applied direct to the sanded timber. If grain filling is required, use a special polyurethane filler.

For staining, use an acid-resistant product. If the manufacturers of the polyurethane do not specify a particular type, buy a water or naphtha stain.

With two-pack varieties, follow the maker’s instructions carefully, as proportions of lacquer and catalyst to be mixed vary from make to make. Mix them thoroughly and allow the mixture to stand for five to ten minutes before use. Mix only enough for the job in hand, as the lacquer remains viable for only about 24 hours.

Apply the lacquer either by brush or by spray. Generally, a heavier film is less attractive in appearance but greater in resistance to damage than a lighter film.

For most jobs, such as shelves, bookcases and vertical surfaces, one or two coats should be sufficient. None of these lacquer finishes achieves maximum hardness in less than seven days, although they are touch-dry in four to six hours.

With brush application, lay the first coat across the grain and finish off by brushing out with the grain. Allow to dry overnight. Lightly sand with fine, dry abrasive paper before applying a second coat of polyurethane.

The final coat should also be sanded to remove high spots, then rubbed down (with the grain) with grade 00 or 000 steel wool. A thin coat of wax polish can then be applied if required.

If polishing unfilled timber, first remove any white deposit in the grain by wiping the surface with a cloth dampened with white spirit.

Transparent coloured polyurethane

Coloured polyurethane finishes will allow the natural grain of the wood to show. They give a tough surface which resists chipping, scratching and even boiling water.

They are excellent for use on new wood that has few blemishes and fillings. When choosing whitewood furniture to be finished with coloured polyurethane, select pieces with a good, unbroken grain.

Old wood that has been treated with paint, varnish or any other finish must be cleaned right down to the bare wood.

Application: clean off all grease and wax with an abrasive and white spirit; do not apply the finish in humid conditions.

Apply the first coat, preferably of clear Hardglaze, with a cloth pad. Leave this to dry for at least six hours, then apply further coats with a paint brush. If you wait for longer than 24 hours between coats, rub down the previous coat with fine glasspaper or a medium grade of steel wool.

Obtain a matt finish, if preferred to the normal glossy finish, by giving a final coat of clear Ronseal Mattcoat.

Clean treated surfaces with a damp cloth. In areas of heavy wear, apply a wax polish for added protection. Cloths used for application arc highly inflammable, so destroy them after use.

Do not use these finishes on linoleum, thermoplastic PVC or rubber.

Coloured polyurethane paint

One-pack opaque polyurethane paints are extremely tough and scratch-resistant and give an ideal finish for nursery and kitchen furniture. They withstand temperatures up to 100°C (212°F) without discolouring, and table tops in these finishes are not harmed by contact with hot plates.

Polyurethane paints are durable when used outdoors. They are available in gloss and eggshell finishes.

Application: no special preparation of the timber is necessary. After a coat of polyurethane primer, apply with a brush or spray unit in the same manner as ordinary paint.

For best results, lightly sand between coats, taking care to remove all dust and allowing not more than 24 hours between applications of successive coats.

Previously painted surfaces do not require priming but do need careful cleaning, to remove dirt and grease, followed by a light rubbing down with abrasive paper. Exposed surfaces need at least two coats; a single coat may suffice indoors if the new paint is much the same colour as the one it is covering.

Most polyurethane paints are touch-dry in about three hours, are ready for sanding within six to eight hours, and are fully hard after three or four days.

Clean brushes or spray equipment immediately after use with white spirit.

Floor sealers

Some floor sealers on the market, such as Bourne Seal, are also suitable for finishing general woodwork and some furniture. They are, in many ways, a compromise between oil and lacquer finishes and are well suited for wood finishing in the home.

They are applied in the same way as oil finishes. They penetrate deep into the timber and, like oil, tend to darken it. With successive coats, a fairly resistant film can be built up if required. This will not have the toughness of two-pack lacquers, but it can be repaired and recoated fairly easily; and with average wear and use it will require little maintenance.

Application: apply with a brush or a pad of non-fluffy cloth to the unfilled timber, working across the grain and well into it. Finish by brushing out or wiping off any surplus, this time working with the grain, before allowing to dry.

Drying is slow, and the surface is best left overnight. Lightly sand between coats to remove high spots.

On all vertical surfaces, such as panelling, and on shelving, one or two coats are sufficient. Leave the final coat for a few days before rubbing down, with the grain, with steel wool, grade 00 or 000. Remove dust and apply a thin coat of wax polish.

Horizontal surfaces, likely to have to withstand harder wear, may require three coats. Further coats can be applied periodically, but only after all traces of wax or grease have been removed.

These finishes can be applied to any timber and are well suited where the extreme hardness of two-pack lacquers is not essential.

French polish

This is a traditional finish and is applied to many valuable antiques. The basic material is shellac dissolved in methylated spirit.

There is little point in French polishing at home except on repair work and when matching existing furniture — although it provides an excellent finish, it is easily marked by heat and liquids.

Various proprietary brands of French polish make the job simpler for the amateur and, applied with care, give a satisfactory result.

Garnet polish, button polish, white polish and transparent polish are all forms of French polish, having a base of shellac and differing only in colour; true French polish is a rich brown, the others being degrees lighter, down to near-transparent.

Techniques in application vary according to the type of polish and the user’s skill. The following serves as a general guide to polishing procedure and should be within the capabilities of a careful amateur.

Preparation: the timber must be well sanded and clean, and the grain filled with a grain filler. Choose the shade of polish you require, bearing in mind that darker polishes darken wood considerably. When matching colour, experiment first on sample pieces of timber. Any staining must be done before applying the polish.

Equipment: the most important implement in French polishing is the polishing rubber; it is with this simple tool that the best work is produced. It consists of a pad of cotton wool, which acts as a reservoir for the polish, and a cover of soft white linen or cotton fabric, similar to a well-worn handkerchief, which acts as a filter.

The rubber must never be dipped into the polish; it is charged by pouring the polish on to the pad with the cover removed. Avoid over-soaking the rubber; the polish should ooze slightly through the cover when a light pressure is applied.

Application: work evenly over the surface with a slow figure-of-eight motion until the timber is coated with a thin layer of polish. The object is to apply a series of thin coats, allowing only a few minutes for drying between coats. Make sure that corners and edges get their full share of polish.

When you have obtained a level and even-bodied surface, the work is ready for the second stage, spiriting off.

Allow the work to stand for at least eight hours, then take a fresh rubber with a double thickness of cover material and charge it with methylated spirit. Wring out until practically dry — the cover of the rubber should feel damp and no more. This is vital, as too much spirit will simply dissolve the polish.

The object of spiriting off is to remove the rubber marks and to give that brilliance of finish associated with French polish. The motion of the rubber should be the same as before, figure-of-eight, with increasing pressure as the rubber dries out. Replace the covers with fresh pieces of cloth from time to time.

Finally, work in the direction of the grain and continue until the surface is free from smears and rubber marks. Leave to harden off. French polish dries quickly but takes several days to acquire maximum hardness.

Shellac-based polishes can also be applied by brush, each coat being allowed to dry thoroughly and rubbed down lightly with fine abrasive paper.

The finish obtained in this way, whilst being satisfactory for many uses, does not compare with French polishing in quality of film and finish.

Ebonising

Ebonising is a process of giving wood a dense, matt, black finish resembling ebony, without obscuring the grain. The timbers most suitable for this finish are the close-grained, whitish hardwoods, such as boxwood, sycamore, beech and birch.

Application: the timber must be clean and well sanded, and the grain left unfilled. First stain the timber with a black dye — Joy make an ebony dye, and Furniglas a black oak dye.

Finish by applying a light coat of matt polyurethane. For greater resistance, two or more coats may be necessary, but avoid forming a heavy build-up, as that can only obscure the grain. When tin finish is thoroughly dry, rub down with grade 00 or 000 steel wool.

Liming

This is a traditional finish for oak. Though not used extensively today, it gives an attractive finish which is still favoured for some church and restoration work. The process entails filling the grain with a dense, white lime paste which will contrast with the surrounding timber.

Application: open the grain with a wire brush worked evenly along the timber in the direction of the grain. If the wood is to be stained, do it at this stage. Next apply the finish, then the lime paste filling Work in that order so that the finish will not discolour the filling. Finally, apply a thin coat of white polish with a rubber, as used in French polishing.

Proprietary brands of liming pastes are made but are not widely available. The paste must be rubbed into the grain by a cross-grain action to fill all the pores. Wipe off the surplus, also across the grain, allow to dry for a couple of hours, then rub firmly with a dry cloth or fine abrasive paper, with the grain.

If you cannot obtain a proprietary paste, you can make a paste yourself. Mix whiting with water to form a stiff paste, or mix unslaked lime with water to the consistency of paint and allow it to cool.

Both mixtures are applied in the same was as a proprietary paste, but the whiting should be followed with two thin costs of white polish, the lime with only one.

Fuming

This, like liming, is a traditional finishing process for oak. It is a method of darkening the timber by exposing it to the fumes of ammonia.

Ammonia 880 is specially formulated for this purpose and is obtainable from some paint suppliers and chemists. The colour achieved is very even and the shade can vary from a light to a very dark brown, depending on the strength of the solution used and the length of the period of exposure.

On oak, fuming is generally more effective than staining and gives the surface an appearance of depth and age which cannot be obtained by any other means. This is why it is used for church and restoration work, where it is often necessary to match in with centuries-old work.

Much work in oak is left rough from the cutting tools and not sanded, and sanding is not essential for fuming. All glue, oil and finger marks must, however, be sanded off to avoid uneven colouring.

Application: to fume small pieces, prepare an airtight box or tent with sticks and polythene sheets to contain the work and two or three saucers with a little of the solution in each. While the actual process is effortless, the difficulty arises in controlling the depth of colour. To assist with this, a small glass or Perspex ‘window’ is an advantage so that you can easily see when the work has achieved the colour required.

Place the saucers evenly around the work. Remember that the fumes will take effect only on exposed surfaces; if interiors and edges of doors are to be coloured, remove doors from cabinets and treat separately.

To fume large pieces, a large polythene tent or a shed is necessary, but it must be adequately sealed off. The fumes of ammonia are poisonous, so avoid inhaling them. Do not carry out fuming inside the house.

It is impossible to give any direction on the amount of time required. Much depends on the timber — some varieties of oak darken more quickly than others — and on the size of the chamber. Fuming may take anything from 1 to 12 hours; should the full depth of colour required not be achieved first time, the process can be repeated with more ammonia. If a number of pieces are to be fumed to the same colour, a time-table should be worked out using the same amount of time and ammonia for each operation.

On completion, remove the work from the tent, expose it to the air and finish it. For preference, use either pure linseed oil or wax polish.

Should any portion be too dark, it can be bleached with a solution of oxalic acid and methylated spirit (oxalic acid is obtainable from any chemist). Apply the solution carefully with a brush, using masking tape to cover the surrounding area. Finally, wipe over with vinegar and allow to dry. This process raises the grain, and a light sanding is needed.

29. June 2011 by admin
Categories: Treatments and Finishes, Woodworking | Tags: , , , | Comments Off on Different Types of Wood Finish

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