POLISHING may be employed to produce varying degrees of gloss according to the type of medium used. All must rely to some extent upon friction for the final levelling and smoothing of surfaces treated, but perfect uniformity of gloss will also depend upon the checking of excessive porosity of the surface.
The three methods of polishing in general use are:—Wax polishing, french polishing, and oil polishing, the last being capable of withstanding long exposure to weather. All can be applied to new timber, or upon stain; or if required, they can also be coloured and made to combine the duties of stain and polish. Wax gives a rather dull gloss; french polish a high gloss; and linseed oil produces a semi-gloss finish.
This term originally referred to the application of a simple mixture of beeswax and turpentine, but is now applied to different proprietary brands of wax base polishes which include varying quantities of other waxes, gums, resinous substances and spirits. These additions to a wax base do, undoubtedly, assist in obtaining a fine polished surface, but the simple beeswax base possesses a characteristic gloss which has its attractions. Although it is often more convenient to purchase a ready-made compound, the preparation of wax polish is simple; precautions must be taken to prevent the ingredients catching fire. A good method is to shred the beeswax into an earthenware jam jar, using just sufficient to half fill the vessel, place the jar in a pan half filled with water and heat over a low flame until the wax melts. Any tendency to boil over can be countered by the immediate removal of the pan away from the flame.
Take the jar of melted wax out of doors, or at least well away from any naked flame before adding the turpentine (or turpentine substitute). This should be added in the proportion of one part of turpentine to two of wax, the mixture being stirred well, and the jar should then be covered to prevent loss by evaporation.
Wax polish imparts a smooth, hard-wearing finish to new hardwood floors or furniture, but several coats rubbed well into the woodwork at daily intervals are required before the best results are obtained. When the more porous softwoods have to be treated, it is advisable to apply a preliminary coat of raw linseed oil (mixed with driers), or a coat of oil stain, in order to reduce excessive porosity. Such work is often carried a stage further and varnished prior to wax polishing; see VARNISHING, p. 179.
It is well to remember that surfaces finished with wax polish cannot be varnished or french polished unless one is prepared to tackle the difficult job of completely removing every trace of wax.
Although the process is not widely known and has the disadvantage of being rather tedious and slow, it produces an extremely tough and durable finish particularly suitable for new hardwoods. Preparation consists of filling holes with plastic wood, sand-papering the whole surface and finally removing all dust.
The oil is prepared by mixing half a pint of refined linseed oil with one tablespoonful of liquid driers. This is applied sparingly with a piece of clean rag, giving about four applications at weekly intervals. The final coat is rubbed briskly to produce a gloss which, when hard, is capable of withstanding hot dinner plates.
While absolute perfection in this craft demands considerable experience, there are many amateurs quite capable of producing a good finish upon straightforward work. Given the right working conditions and materials, any beginner should make good progress, in a few hours.
Conditions of dryness and warmth are of great importance. A cold draught, or damp atmosphere is almost sure to cause French polish to dry with a permanent whitish bloom, or with considerable loss of brilliance.
Brown french polish should be prepared from the very best quality orange shellac, or button lac. White french polish should be made from the best bleached shellac. Both can be bought prepared.
A stock mixture contains 4 to 5 oz. Of shellac for brown french polish dissolved in one pint of methylated spirit or industrial alcohol. The standard mixture for white french polish contains approximately 6 oz. Shellac dissolved in one pint of methylated spirit or industrial alcohol.
If the polish is to be brush-applied, the addition of one or two ounces of gum benzoin, or sandarac, will improve the gloss. The resin dissolves in about 24 hours, after which time the mixture is sieved through muslin, and bottled.
Other requisites will vary according to the demands of each class of work, but a fairly complete stock includes the following:—spirit stains, water stains, methylated spirit, plastic wood, grain filler, No. 00 sandpaper, refined linseed oil, camel hair mops, cotton wool, and clean calico, the last two being required to make rubbers for the application of the french polish.
Preparation of surfaces and polishing are generally carried out in clearly defined stages, in the following sequence:—(a) stopping and smoothing down, (b) staining, (c) grain filling (essential with open grained and soft woods), (d) oiling in, (e) bodying up, (f) spiriting off. Both new and old work should, as far as possible, be dismantled, handles and other obstructions being removed to allow free play for the rubber.
Cracks and nail holes may be stopped or filled up with plastic wood, which hardens so rapidly as to permit a general glasspapering of the surface within half an hour. Always rub in the direction of the grain, using a flat block of cork inside the glasspaper. If this fails to level the surface, a carpenter’s scraper must be employed. Either method will clean as well as smooth the work, but any rust or ink-stains will have to be bleached out by several applications of oxalic acid solution.
Chemical staining, of considerable value as a means of darkening the softer parts of wood grain, thereby increasing contrast, may be used as an alternative to the ordinary water stain but it may also precede the application of a water stain. The usual materials dissolved in warm water, are (a) washing soda, (b) Epsom salts, (c) lime, (d) ammonia, or (e) bichromate of potash. The staining intensity of the solution of one or other of these materials should be determined by testing, and altering the proportion of water or stain material to suit.
Water stains are available in several forms, chief of which are the ready-prepared powder colours, alkaline dyes, concoctions of tea, coffee, saffron, turmeric, etc.; and the slightly opaque Vandyke brown, mahogany lake, burnt sienna, etc. They may be applied with either a brush or a sponge.
Spirit stains, obtainable in powder form, are dissolved as required in methylated spirit. These have the advantages of being quick drying and deep penetrating and can also be used to colour french polish. A soft brush should be employed for the application of spirit stain, the work being covered a section at a time, and particular care being taken to finish off neatly and squarely at each joint, without overlapping upon the adjoining section.
Where the timber has open pores, it is quicker to fill these with grain filler, rather than with repeated coats of polish. A reliable composition is made from whiting, turpentine, and an appropriate colouring matter such as umber, raw sienna, mahogany lake, etc., which may be in either powder form or ‘ground in linseed oil. Mix to a creamy consistency and rub well into and across the grain, using clean rag as a rubber . Surplus filler should be removed by fine sandpaper.
This simply involves a sparing application of linseed oil to check excessive porosity of the dry filler, a clean rubber being employed for the purpose.
This stage is mainly concerned with building up the body or thickness of the shellac, and also with the production of a smooth level surface. The first one or two coats of polish may be brush-applied, the stock polish being thinned with an equal amount of spirit. Always allow time for the hardening of each coat, and sandpaper whenever necessary, between coats. Use No. 00 sandpaper.
The rubber, cotton wool, wrapped in two layers of calico, is employed for all later coats. This is fed at intervals with half strength polish, the rubber being unwrapped to permit these additions to the top side of the wool. The polish can thus penetrate slowly and evenly to the face of the rubber, enabling it to be used in a semi-dry condition. The rubber must be kept on the move in a series of overlapping circles, any tendency to ‘stick’ being prevented by the addition of a very small quantity of linseed oil to the face of the rubber. The best method of doing this is to allow one drop of oil to fall on the tip of the finger, then rub the finger tip on the face of the pad so as to make an even dispersal of the oil. This procedure should not be resorted to very frequently if it can be avoided, or an oily sheen will soften the brilliance of the finished surface.
A separate rubber charged with quarter strength polish and applied in long strokes following the direction of the grain, should remove any rubber marks and produce a uniform gloss . The work is then finished with a clean rubber barely moistened with spirit only.
These are prepared by washing with a warm solution of washing soda, followed by a rinse of clean water. Repair small defects with plastic wood and touch up with coloured polish. The work is then bodied up with the rubber, using slightly coloured polish to restore richness of hue.