POLISHING WOOD WHICH HAS ATTRACTIVE GRAINS
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.
Staining.
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.
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.
Finishing.
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.
Must read: Types
of Paint Used in Construction and Its Uses
Must read: Guidelines
of Home Painting
Must read: How
to do whitewashing and colour washing
Must read: How
to Do Painting With Cement Paint
Must read: How
to Do Painting With Dry Distemper
Must read: How
to do painting of plastered walls with plastic emulsion paint
Must read: How
to do painting iron and steel with enamel paints?
Must read: How
to do painting new / old woodwork with synthetic enamel paint
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