Preparation of the wood surface for processing

Preparation of the wood surface for processing

The wood to be painted must be dried to a moisture content of 10-12%, and the wood to be varnished and polished to 8%. For wood surfaces with high humidity (20 to 30%), paint and varnish coatings are poorly accepted and wear out quickly. The reason for this is that the wood's dimensions decrease in the radial and tangential directions during drying, and increase during wetting. If the changes in the dimensions of the wood are within larger limits, then the elasticity of the paint and varnish becomes insufficient, and when the wood dries, the shell also wrinkles, and when it gets wet, it separates from the wood or tears in several places.

The quality of the paint and varnish coating is all the better if the wood surface is better prepared. Therefore, the wood, which should be coated with painting materials that form an opaque scrum, should be planed on planers with a wave length of 4 to 2.5 mm, and then sanded with sandpaper 120 so that the cleanliness of the surface corresponds to class VI or VII. The surface to be varnished must be planed on planers with a wave length of up to 2 mm, sanded with sandpaper 120 - 140 and must correspond to VIII or IX cleanliness class.
For polishing with shellac polish, the surface of the wood must be planed on planers with a wave length of up to 1 mm, and sanded on an iron (cycling machine), then sanded with sandpaper 140 - 170. The cleanliness of the surface must correspond to X class.

Before painting, all unevenness on the surface should be smoothed and filled (knots, scratches, cuts, etc.). Openings from dropped knots should be plugged in such a way that the direction of the fibers of the plug coincides with the direction of the fibers of the elements.

Before polishing and varnishing, the surface of the wood should be lightly moistened with water, and then, after 2 to 3 hours of drying, smooth it with sandpaper 170 to 200, placed over a pad made of a piece of soft wood with dimensions of 100 X 100 mm. Sanding must be done along the grain of the wood with even movements, after which the product or element should be rubbed with a piece of soft cloth and the dust should be cleaned with a brush.

Before coating the wood with paints and varnishes that form opaque coatings, it is primed with oil or another primer. Then, if necessary, local puttying and puttying is done over the entire surface. The primer should close the pores, bond the coating with the wood and improve its adhesion. The color of the primer and putty used for filling should match the color with which the product should be painted. During varnishing and polishing, grouting is done with special transparent primers or varnishes and polishes, which will also be used for processing, and for this purpose, they should be significantly graded. For example, for high-quality treatment with shellac polish, the wood surface is primed with 10% shellac polish.


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