الزيوت والراتنجات والمواد الأسفلتية ٤_a , من كتاب تكنولوجيا التصوير د.م محمد حماد

Pentaerythrite is a neutral resin and more solid than rosin. It is used under the name “ester gum” in alcoholic or cellulosic gomme ester varnishes used for wood, as well as fatty varnishes.

acide abiétique lévopimarique maléique resins: They are produced from the condensation of maleic acid anhydrides around 200-5250 m on the double-armed resinous acids of rosin (abietic acid and levopimaric). The acidic condensation product is converted to an ester in union with a polyalcohol (glycol, or pentaerythrite) to form a solid resin, but it can also be broken. It is neutral and its fluidity depends on the percentage of the amount of maleic acid anhydride in it.

If the esterification with a polyhydroxy alcohol was preceded by a graded process that spreads the double arms of the resin acids, then the resulting resin is known as hydrogenated rosin, and its color is dull and does not yellow as a result of exposure to light.

(C)

The resins richest in maleic acid anhydride are the alkyd resins resulting from multiple acids with multiple alcohols and hardened by heat, modified in combination with oils that improve their ductility, and they form the flexible material for enamels that solidify by placing them in ovens. Species with less maleic acid anhydride (containing more rosin) are also solid, but fusible resins, and are used in some greasy varnishes. Finally, those that have the lowest percentage of maleic acid anhydride similar to ester gums are used in alcoholic and cellulosic varnishes.

(D) Other transformations of rosin: rosin can be combined with some industrial resins (phénoplastes of phenolic compounds and glyceric resins, with a phthalate that improves its solubility and reduces the cost price in industrial works (glycerophtalique) which

By heating the rosin between 5300 and 5400 C, a chemical reaction occurs through destructive distillation or decarboxylation of the resin acids, resulting in resin oils used in printing and engraving inks if they are dry, or lubricating oils if they are not dry.

- les copals

Cobalts are resins that are not from Europe, but rather resins from hot countries, and their composition is more complex than that of rosin. It is now often used in the manufacture of varnishes and resins that are less expensive and more stable. They include:

(a) Frozen cobalt extracted from a tree in an old place, and it may run on the sand and mix with it, so it is extracted from the soil. In its old age, it underwent transformations that increased its hardness and melting point (150 to 5350 C), and it became insoluble in solvents. It does not dissolve in oil except with the temperature between 300 and 350 Celsius, and thermal copal Congo is also used sometimes in the manufacture of fatty varnishes

(b) Green cobalts, such as rosin, which is extracted by stripping the bark of the resin-producing tree.. Contrary to the above, it is directly soluble in oils and some solvents. In this group we can put dammar resin, gomme laque, sandaraque (which is similar to mastic in its appearance) and soft manel resin. They are also used in cellulosic varnishes for light woods, in fatty varnishes and depending on the nature of their solvents in alcoholic varnishes (lacquer) or in Petroleum solvents (white dammar resin varnish). manual tendre

Asphalt products:

Asphalt materials are solid, dark-coloured groups, consisting of compounds of non-volatile solid and liquid hydrocarbons. They mainly include natural bitumens (such as gilsonite), which are similar in origin to petroleum and coal and petroleum tar, which are the distillation residues of coal tar and crude oil, respectively. They form When dissolved in hydrocarbons (xylol and petroleum solvent) black varnishes are given after the evaporation of the solvent a layer that does not save water and resists acids and alkalis thanks to the chemical inertness of its constituent hydrocarbons. Linen oil is always added to it to improve its viscosity.. and above all, solid industrial products are added to it. Coumaroniques, phenolic and epoxides coatings, which increase their hardness and resistance to heat and chemical agents.Therefore, asphalt products in industrial works are an excellent waterproofing primer over wood and surfaces, and anti-rust coatings (which are painted with aluminum powder) in carpentry works and steel epoxydes phénoliques.

Some types of varnishes are made using asphalt materials, and one of their most important characteristics is their water-repellent qualities and their luster. They also do not undergo developments such as oxidation, polymerization or condensation. Rather, the asphalt remains as it is and becomes subject to dissolution in solvents (such as carbon disulfide, petroleum, mineral turpentine, and dusting). . And if a paint is applied over it that contains these solvents, it will make it. It is prone to liquefaction and mixing with the second paint.. Among the defects of asphalt varnishes is their sensitivity to thermal vibrations of the atmosphere, and this results from their natural properties as they soften with heat, especially in hot, rugged areas.
Methods of application and application of varnishes and coatings

There are several ways to use varnishes and coatings, including manual methods with brushes, whether large or small, rolling cylinders, stamps or knives, as well as the wet or dipping method, then mechanical methods such as spraying with a gun or airbrush of various forms, as well as methods in which electricity is used .. and we will talk here About the methods that interest the artist in his work, which are Bedouinism and spraying with a gun or airbrush of all kinds

- Manual methods: - This is the method that has been used since ancient times and includes:

(1) Using a large or small brush, which is a common method used in industrial works for protection, and in artistic and decorative works. The brush used is usually made of pig hair, animal hair, or synthetic fibers (nylon) and soft, branched fibers. Sometimes horse or mule tail hair is mixed with these fibers, which is less expensive.

The use of the brush is suitable for decorative paints and oily varnishes, whose slow drying makes them easy to use, especially on wide surfaces. The brush is also used in building works, decorative works, or painting and painting on walls

(B)

Other Bedouin methods, such as using rotating cylinders covered with felt, sheepskin, or sponge nylon. It is usually used on wide surfaces instead of a brush.

As for the use of stamping or printing, it is used in repeated motifs

But this method is slow in varnishing and furniture painting, and the knife is used only in the case of putty and the like to apply thick colors with the help of a narrow or wide putty knife, depending on the nature of the work itself.

2- Using the varnish with a gun: This method includes: spraying the varnish or paint with a compressed air stream. This method became popular after 1918 with the appearance of cellulosic varnishes whose rapid drying does not allow the use of a brush. It began with a simple mouth-blowed airbrush (such as a pastel fixative spray or a koji airbrush) and is now commonly used with synthetic resins, cold-drying varnishes and lacquers, emulsion paints, kiln enamels, furniture coatings, car and aircraft bodywork, etc. The most important types are: