The Technique of FURNITURE MAKING

CHOICE OF GRITS

For all preparatory sanding and levelling off an 80 grit firm-backed cabinet-paper is suitable, and coarse-grained woods such as oak or teak rarely require any finer treatment. For close - grained woods the first coarse sanding should be followed up with a 120 grit finishing paper, and finely veneered surfaces with 180 grit which can be used with a circular movement over mitred corners, etc. For the most delicate work and for easing down polishes a 240 grit can be used. The foregoing are. of course, only suggestions based on the practical experience of the writer, and as individual touches differ other workers may prefer coarser or finer papers. For comparable results with orbital sanders the grits can be coarser, i. e. 60 grit for preparatory work, followed up by 100 grit, and 150 grit if necessary.

Some woods are woolly textured so that the grits tend to crush rather than cut the fibres, and these should be given a very thin wash coat of white french polish or cellulose lacquer (5 parts spirit or thinners to 1 part polish), and allowed to dry hard before the final sanding. The wash coat raises the grain and sets the loose fibres in an upright position so that they can be cut off. In the best work surfaces are always 'flared off by damping them with water to raise the grain. This flaring off can be done several times if necessary, but wherever water is used it is essentialto dust the surfaces very thoroughly with a stiff brush, for if they have been scraped with steel scrapers iron mould stains may appear, which will have to be bleached out with oxalic acid. The time spent on careful sanding will be well repaid in the excellence of the finished furniture.

All abrasive papers should be stored in a dry place (ideally at 70° F [21° C] and 45 per cent humidity) and warmed slightly before use if the backing is at all damp.

Hardness of grits

Relative hardness of the various types of abrasive in comparison with the diamond which is given a MOH value of 10 are as follows:

SELECTION OF HAND - AND MACHINE-SANDING PAPERS

Aluminous oxide Glue or resin

finishing-paper A 400-60 Open Wood

All finishing operations in hard - and softwoods and flattening cellulose with white spirit/wood alcohol

Garnet finishing-paper Glue or resin A 320-60 Open Wood

Finishing of softwoods, etc.