Wood varnishing

Wood products are covered with colorless finishing materials that preserve or bring out the beauty of the texture and color of wood. This is achieved by waxing, varnishing and polishing..

However, it should be borne in mind that only a perfectly processed surface can withstand the test of varnish or wax, since the transparent finish does not hide, but only more emphasizes the imperfection of the finish: risks, scratches, dents.

WAXING

Of the old traditional transparent finishes, wax mastic finishes are currently used. It is recommended for large products (wall panels, frames, sculptures).

For the preparation of mastic, beeswax or its substitute – ceresin 67.

After melting wax or ceresin in a water bath, a solvent (turpentine or gasoline) is added to it in a ratio of 1: 2 by weight.

After applying hot mastic with a brush and drying for 1.5-2 hours, the surface of the product is rubbed to shine with a soft hair brush or coarse cloth.

After a day, the operation is repeated.

Wax mastics fill the pores of wood well, giving the surface a soft silky sheen. To protect the wax coating from mechanical damage and moisture, the product is coated with alcohol varnish. Nitrol varnishes cannot be used for these purposes due to the lack of adhesion to wax.

Varnishing

Traditional finishing with alcohol shellac polish, used in the practice of folk crafts, has now given way to finishing with nitrocellulose compounds.

Souvenir products decorated with carving are finished with nitrocellulose varnish (nitro varnish), followed by polishing with nitro-resin.

Before varnishing, the product is primed.

The paint and varnish industry produces ready-to-use primer formulations. It is possible to prime under varnish with drying oil or thick varnish. These soils are used in their pure form or they are diluted with thinners and, if necessary, pumice powder, chalk, talc, kaolin, tripoli, starch, wood flour or pigments are added, if it is necessary to adjust the color of the soil to the color of the wood itself.

After priming, fill up.

When processing wood with cutting tools, the hollow anatomical elements (vessels) are cut and irregularities are formed on the surface of the wood. In species such as oak, ash, walnut, the amount of structural irregularities is significant. Therefore, before varnishing or polishing these rocks, it is necessary to reduce the magnitude of these irregularities. For this, a special operation is performed, which is called porofilling..

Fillers are formulations intended for rubbing into the pores of wood in order to close them before applying transparent coatings, and forming, like primers, a lower layer of paintwork.

Depending on the property, the filler is applied to a previously primed or unprimed surface. A layer of filler helps to reduce the consumption of paints and varnishes and reduce the sagging of the coating in the pores during the operation of products.

The filler consists of a liquid part (a solution of a film-forming agent, driers and plasticizers in a mixture of volatile solvents) and a filler. The liquid part of the filler is designed to bind the filler and reveal the wood grain, give the filler elasticity and create a thin varnish layer on the surface.

The filler must have a certain Dispersion: not be coarse-grained, as this prevents it from being rubbed into small pores, and too fine-grained filler poorly fills the pores and gives a large volumetric shrinkage.

The filler is applied to the wood by hand with a swab or spatula.

It should be borne in mind that fillers veil the texture of the wood, so the excess must be removed and the surface wiped clean..

Fillers are usually supplied as two components – a film former solution and a filler.

The components are mixed before use, since the suspension of fillers is unstable – during storage, a dense, hardly soluble sediment is formed (that is, the filler is stratified).

Fillers can be colorless or tinted. Fillers KF-1, KF-2, PM-11, LK have found the greatest application.

Of great importance during operation is the adhesion strength of the paintwork to the wood surface, the so-called adhesion. It is conditioned, first of all, by the quality of paints and varnishes, conditions of their application and drying of the coating. High adhesion can be achieved only if homogeneous compositions are used in the finishing: nitro varnish but nitro primer, oil varnish but oil primer, etc. Otherwise, the finishing layer quickly cracks and then exfoliates.

Currently, the main way to achieve transparent. finishing is varnishing.

Varnishes are divided into two groups by the nature of film formation: those that form a film only due to the volatilization of solvents (for example, alcohol, nitrocellulose) and that form a film as a result of chemical reactions of polymerization and polycondensation, as a result of which they pass into an insoluble state (for example, oil, polyester, polyurethane, urea formaldehyde).

For a long time, alcoholic varnishes – solutions of resins (shellac, iditol, etc.) in high-degree alcohol – had been widely used and were indispensable for finishing wood products. In modern practice, nitrocellulose varnishes are most often used. They give a strong, elastic, fairly weather-resistant, quick-drying film. Nitrol varnishes are divided into two groups: hot-applied varnishes (at a temperature of 70-75 ° C) – NTs-223, NT-225 and cold-applied varnishes (at a temperature of 18-23 ° C) – NTs-216, NTs-218, NTs- 221, NTs-222, NTs-224, NTs-296 (former NTs-316). Varnishes NTs-49, NTs-243 give a matte film.

The nitro lacquers are brought to the working viscosity with solvent No. 646, with the exception of NTs-223 lacquer, for which the RML-315 solvent is used. All of the listed nitro varnishes can be applied to the surface of products with a brush, swab or by spraying, NC-243 varnish can also be applied in bulk.

Oil varnishes form a strong, elastic, weather-resistant, but not enough decorative film with a strong hard gloss. According to their composition, they are solutions of solid natural and synthetic resins in drying oils with the addition of desiccants (compositions that accelerate the drying of oils) and a mixture of volatile organic solvents (turpentine, white spirit, etc.). Natural readily soluble resins include copal, amber, rosin processing products. Copal varnish is considered one of the best oil varnishes. Drying oils are used as the main components – linseed, hemp, tung.

For wood finishing, oil-resin varnishes 4C, 5C, 7C were used earlier – for light species; 4T, 5T, 7T – for dark rocks (drying in 48 hours), and now they use pentaphthalic varnishes PF-231, PF-283 (formerly 4C).

Varnish PF-231 – light, forming a durable glossy coating, drying in 72 hours at a temperature of 18-23 ° C. Applies well both by brush and spray.

In many respects, oil varnishes made from natural and synthetic resins are close to each other and can be interchangeable.

Polyurethane varnishes have good water, atmosphere and wear resistance, which are applied by spraying and pouring with cold curing or with heating to 45-50 ° C. In terms of properties, they are close to polyester varnishes, and in some respects they are superior. Known polyurethane gloss varnishes of the grades 1.653.031, 1.641.0231 and 17642.0230, which are applied by pouring and spraying, semi-matt varnish 1.653.0300 two-component, matt one-component, spray applied.

Amateur carvers use waterproof matte varnish UR-277M with Supersec 3240 hardener and RL-227 solvent at the rate of 82.5% hardener per 100 g of varnish, and solvent – to the required viscosity.

Varnishes are applied to a dry wood surface, free from dust, in uniform thin layers without smudges about 3-5 times. Dry each layer. Before coating with the next layer, the previous one is treated with used fine sandpaper. This ensures the alignment of each layer and better adhesion between the layers..

Finished products can be soaked several times with hot drying or semi-drying vegetable oil or natural linseed oil. The oil or drying oil should be heated in a water bath (in a glue boiler) and applied to the product with a wide brush or a swab fixed on a wooden handle.

When the first layer of linseed oil or oil is absorbed and dries, the second is applied and dried, and then the third. When using oil, keep in mind that it takes a very long time to dry. To speed up drying, small products can be kept in the oven of an electric or gas stove for 10-12 hours at a temperature of 90-100 ° C.

Features of finishing products for food.

For a transparent protective coating of decorative and applied products intended for food products (candy bowls, salt shakers, bowls, trays, bread bins), wax mastics, alcohol or nitrocellulose varnishes, linseed, hemp, camelina, soybean, poppy or sunflower oil should be used. Tung oil is the third in terms of drying capacity (for linseed – taken as a standard – and hemp), but it cannot be used because of its toxicity. It is also undesirable to use varnish and oil varnishes, since they contain special additives – driers that accelerate drying, which, as a rule, are oxides, peroxides and salts of lead, cobalt and manganese.

POLISHING

To give the wood surface a stable velvety shine, polishing is used. This is the best type of finish, in which all shades of color and wood grain are revealed and deepened on the surface. The polished surfaces of walnut, Karelian birch and mahogany are especially beautiful. Naturally, the surface must be perfectly prepared for polishing. For a long time this method was the only and rather widespread, but due to its high labor intensity (150-200 thin layers are applied with intermediate drying) and duration (the process lasts more than a month), it has now been replaced by more productive.

The decoration of the products must correspond to their purpose. For example, wax is used to cover those items that are not handled or they are little taken in hand; furniture must have a finish that can be cleaned well,

Glossy or matte finish?

In wood products, one can clearly see the very diverse attitude of artists and craftsmen to surface finishing. Others polish it to a mirror shine, finish with mastics and varnishes, but there is also a desire to preserve the natural beauty of wood, that is, to leave the product unpainted and unvarnished. But unfinished products quickly lose their appearance. Craftsmen strive to find such a finish that would allow, while preserving the original appearance of the product, its novelty, leaving the feeling of the living natural beauty of wood. Therefore, more and more often, when finishing, craftsmen use wax mastics or special matte varnishes that do not give a shiny, brightly glittering (glossy) surface, leaving it soft, velvety.

The varnish can be made matte. If you were unable to purchase matte varnish, do not be upset.

It can be made from ordinary glossy oil varnish by adding up to 0.5% of laundry soap and up to 10% of white spirit.

The soap solution is prepared as follows:

Laundry soap (40%) is cut into shavings, dissolved in a small amount of hot water (at a temperature of 70-80 ° C).

The resulting solution is mixed with white spirit and, with stirring, is introduced into an oil glossy varnish. When soap is added, the strength of the lacquer film is somewhat reduced, so it cannot be washed and wiped with damp rags. Clean products with dry brushes or with a vacuum cleaner