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Even though exterior woodwork needs painting for durability, interior surfaces and furniture which are made of wood with attractive grains (as in teak wood) can be given a finer polish with the following clear finishes:

1. Clear and shellac varnish (varnishing)

2. Spirit of French polish (French spirit polishing)

3. Melamine based finish (melamine finishing)

4. Polyurethane-based finish (polyurethane polishing)


Method of Polishing Wood

The polishing of wood is carried out by the following four operations:

(a) Knot filling, glue sizing and filling of holes

(b) Staining

(c) Sealing

(d) Finishing by varnish, spirit polishing or clear paint


Knot filling.

The first operation is knot filling, glue sizing and filling of holes. Glue size is a glue-like substance that stiffens with time. We first rub down the wood with fine emery paper to expose the grains. Then we apply glue size to seal all the pores in the wood to prevent the absorption of moisture and the oil from the varnish. First, a thin layer of size is applied all over the surface. When dry, it is rubbed down smooth with sandpaper and cleaned. A second coat is also usually applied and rubbed down with fine sandpaper and cleaned. Alternately a transparent wood filler coat may be used. Any holes, etc. are also filled with metal paste (used for automobile repair) and rubbed down. The filler coat can also be prepared by mixing 1.5 kg of whiting (ground chalk) with 1 litre of methylated spirit.



This second operation, staining, enhance the beauty of wood. Desired stains can be applied evenly by brushing. Staining of furniture is usually carried out by dissolving staining colour powder in clear varnish and applying it to the wood.



Sealing is the third operation. A suitable readymade sealer available in the market is applied on the stained surface to seal it from subsequent coats.



The fourth operation is the final finish. It is carried out by one of the following finishes.

(i) Finishing by varnish.

It is obtained by applying two or three coats of varnish. Usually, Copal varnish obtained by dissolving Copal resin in denatured spirit is used. Each coat should be applied with a full brush and allowed to dry. Special fine hard brushes, and not ordinary paintbrushes, are to be used for this procedure. The surface is then rubbed down and flattened after each coat with fine sandpaper. The final finished surface should be uniform and glossy. (Types of varnishes have been covered in the book on Building Materials.)


(ii) Finishing by French spirit polishing.

French polish is a product obtained by dissolving shellac in commercial alcohol. The surface for French polish is prepared as already described by first sizing the knots and coating it with a filler compound such as that made of mixing 1.5 kg of whiting (ground chalk) with 1 litre of methylated spirit. This process is to fill the pores. It is allowed to dry. Then it is rubbed down with sandpaper and cleaned. On this prepared surface, French polish is applied with a polishing pad of absorbent woollen cloth covered with a fine cloth (and not by brush). The pad is moistened with polish and then rubbed hard with quick light strokes along the grains of the wood. On drying, the surface is rubbed down with fine sandpaper and cleaned. Several coats are applied to get the described finish.


(iii) Finishing by melamine-based and polyurethane-based finishes.

These special paints are available as clear paints. Melamine-based paints are available in transparent and opaque finishes and polyurethane paints are available as a clear finish. Polyurethane paint is cheaper and is recommended for the clear painting of external doors and windows. They also have a good tolerance to climatic change and humidity when compared to French polish.


Note: French polish is cheaper than varnish but the surface gets easily scratched and stained. It does not withstand weathering and hence is suitable only for inside work, for polishing furniture, etc. It is not suitable for external work.

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