The large group of the materials, which are the solutions of the film-forming substances (resins or polymers) before the organic solvents or the water, is called varnishes. After drying they form solid transparent (colorless or colored) film.

Varnishes are used for obtaining the transparent coatings, when it is necessary to protect and simultaneously to preserve or to especially emphasize the structure of the painted surface, mainly the valuable species of wood. In this case the varnish is brought down the prepared surface of article. Varnish as the last layer before the system of multilayer coating will give a good exterior view to it and will increase the performance properties.

The assortment of varnishes is sufficiently diverse. Bituminous, oil, alkyd, nitrocellulose and other varnishes in private life most frequently adapt.

Bituminous varnishes are obtained based on bitumens of special stamps with the addition of different resins, oils. During drying bituminous varnishes form the black film, which possesses resistance to water and some chemical reagents. However, the anticorrosive properties of bituminous film due to the atmospheric conditions are insufficiently high. Most frequently bituminous materials (varnish [BT]-577, paints [BT]-177 and [BT]-184) use for the temporary protection of metal, since they are considerably cheaper than other materials.

Oil varnishes are obtained as far as the dissolution of natural or synthetic resins before drying vegetable oils with the addition of siccatives and solvents. Of the natural resins more frequently use rosin, shellac and amber. Copals, to [dimmaru], sandarac, to paste, an acaroid, imported from India and other countries, use in essence for the artistic and decorative painting. Natural resins, besides rosin and amber, are scarce materials and adapt [ogranichenno]. Them they substitute by the synthetic resins (polymers) - by perchlorovinyl, alkyd, coumarone-indene, phenol-formaldehyde and other

As a rule, oil varnishes form the solid clear sheets of yellowish color. As a result of the low weather resistance of coatings the oil varnishes are used for finishing the articles indoors, for example for giving of luster to the worn coatings the wooden sexes.

Spirit varnishes and varnishes obtain as far as dissolution before alcohol of some natural of resin- shellac, sandarac (concentration of varnish 30-45%, varnish 15-25%). These materials give coating [s] grow prettier by mechanical strength and by adhesion to different surfaces, by high luster. Coatings are polished well, but they are characterized by low water resistance.

Oil and spirit varnishes are let out before insignificant quantities because of the scarce and expensive natural raw material. They adapt predominantly for the special purposes, for example with the production of musical tools.

[Neftepolimernye] varnishes - new group of the varnishes, which are substantially cheaper than oil-tar, but are capable of replacing the latter, exceeding them on the resistance to the action of the cleaning agents and different reagents.

These varnishes (Np -2129, Np -2130) are obtained in the form compositions, the solutions of [neftepolimernykh] resins before the organic solvents for the sake of different modifying additives.

Alkyd varnishes - most common in private life from the varnishes used. Are the solutions before the organic solvents of synthetic alkyd (pentaphthalic or glyptal) resins. The films of alkyd varnishes are solid, are transparent, weakly painted; they possess grow prettier by adhesion to different surfaces, they are water-resistant. They adapt both for the internal and for the external works. (Although traditionally varnishes rarely they are used with the fulfillment of external works.)

Before the custom alkyd varnishes are erroneously called oil. This is erroneous because although with the production of alkyd resins adapt vegetable oils, by the chemical composition and the structure alkyd varnishes differ based on the oil, and about the properties they substantially exceed them.

Let us give the basic information about the most suitable for the application before the household conditions alkyd varnishes.

Varnish [GF]-166 (pF -283) is the solution of modified by vegetable oils of [alkidnoi] glyptal (pentaphthalic) resin before the organic solvent for the sake of the addition of siccative nF -1. It gives uniform glossy clear sheet. It is intended for the coating by means of the oil paints, the wooden and metallic surfaces outside and indoors. It is brought by brush, roller or paint sprayer. It is diluted if necessary by mineral spirits or solvent RS -2. Expenditure of varnish for single-layer coating - 70-75 [g]/[m]2. Duration of drying single-layer coating - 48 hours.

Varnish [GF]-177 is the solution of the glyptal resin, modified by cotton-seed oil, before the organic solvents for the sake of the addition of siccative. It is intended for coating of the wooden, grounded or painted metallic surfaces, exploited due to the atmospheric conditions. It is recommended also for painting the kitchen furniture. Before the work varnish they dilute by solvents 649, 650, RS -2, solvent or turpentine and filter through 2 layers of gauze. To wooden surface for the safety it should be additionally processed by imputrescible compositions, conducted [porozapolnenie] and painted (for example, processed by mordant). The grounded or previously painted metallic surface should be [proshlifovat] and wiped through for the sake of mineral spirits. The duration of the drying of single-layer coating - 24 hours, by brush the second layer of varnish applies after 36 hours. Expenditure of the varnish for single-layer coating - 60- of 90 [g]/[m]2.

Alkyd- carbamide varnishes ([MCH]-52) are the solution before the organic solvents of the composition of alkyd resin for the sake of the aminoformaldehyde (urea-melamine-formaldehyde) or undertaken together before the specific relationship. They dry in air at a normal temperature only during the introduction before them before the use of the given quantity of the acid catalysts. With the hardener the period of the fitness of varnish is limited from several hours to several days. Such materials can dry, also, without the hardener, but with the hot drying (80-120°[S]). Alkyd- carbamide varnishes with the hardeners form the sufficiently rapidly drying in air films, which are characterized by the increased hardness, by good water and by wear resistance. Adapt these varnishes for coating of parquet sexes, furniture and different articles through the tree, exploited indoors.

Nitrocellulose lacquers (nitrate dopes) are obtained by the dissolution of cellulose nitrate before the mixture of active organic solvents. The properties of varnishes are regulated by introduction beside the composition of different resins (alkyd, aminoformaldehyde and other). Nitrate dopes form the solid transparent, practically colorless quick-drying films. Most frequently nitrate dopes ([NTS]-221, [NTS]-222, [NTS]-218, [NTS]-228 and other) use for varnishing the articles through the tree.

Polyurethane and alkydurethane varnishes give the films, which possess extremely high by mechanical strength and by wear resistance. By them varnish parquet hems, furniture, musical tools.

Epoxy varnishes are the solutions of epoxy resin before the organic solvents. Before the varnishing to them is added the hardener, whose quantity depends on the type of resin and hardener, conditions of consolidation and it is indicated before the instructions beyond the application. Varnish films possess high waters and alkali resistance, mechanical density, adhesion to different materials; however, it is insufficiently weatherproof. In private life epoxy varnishes frequently are used for the preparation of putties, gluing, production of the souvenirs and other purposes.

Polyacrylate varnish [AK]-156 is the solution of acrylic copolymer before the mixture of organic solvents for the sake of the additions of organic dyes. It is intended for creating the decorative coating along the metal, the glass and the tree of different species. Varnish gives the required nuance to wood and emphasizes its texture, it protects materials from the atmospheric action. It is let out different colors: colorless, yellow, orange, red, blue, green, brown. Before the putting the varnish should be thoroughly mixed; if necessary it is possible to dilute by acetone or diluent 646. The duration of the drying of each layer - 24 hours, for the single-layer coating will be required 60 [g]/[m]2 of varnish.

Especially one should stop against the special varnish compositions, utilized for the protection of wood. These are the varnishes “Of [luksol]” (Czech Republic) and “[Pinoteks]” (Finland). They reliably protect wood from the formation of mould and rotting for several years.

The varnish “Of [luksol]” is the solution of the mixture of alkyd resins before the organic solvents for the sake of the additions of dispersed organic and inorganic pigments. It is intended for the external and internal surface finishing from the tree of different species, it gives the required nuance to wood and emphasizes its relief, simultaneously protecting wood from the atmospheric action, mould, the wood-attacking caps and insects. Varnish can be used for finishing of garden houses, furniture, windows, doors. It is let out different colors: light yellow, yellow, dark brown (rose wood), green, red-brown ([makhagon]), black (ebony), brown (chestnut).

The varnish “Of [pinoteks]”, giving surface decorative form, simultaneously protects wood from the mould, rottings, damages by the insects also of atmospheric actions. It is let out different colors. It adapts for the external and internal work. By it is possible to process wooden external walls, cornices, doors, windows and so forth

Source: PROEKTSTROY.RU