Shellac, a unique organic substance. Resins The link between shellac and the cosmetics industry

During the swarming period, the insects sit on tree branches and absorb tree sap, digest it and secrete a resinous substance. The lacquer peel is harvested in June and November. After it is subjected to grinding, washing and drying to obtain a loose varnish mass. Later, the varnish, placed in canvas bags with the addition of 2–3% arsenic sulfide, is melted over a charcoal fire. The molten lacquer is pressed through the canvas, after which it is melted again and cast into rectangular molds. By drawing from rectangular bars, ready-made shellac plates are obtained.

Applications

• Shellac is used to make varnishes, insulating materials and in photography.
• Before the invention of vinyl in 1948, shellac was used to make phonograph records.
• It is used in pyrotechnics as a combustible substance, for example, for signal lights.
• Shellac is edible and is used as a coating for tablets, sweets and other things (it is designated in the composition as food additive E-904).
• Alcohol-based shellac varnish is used in the furniture industry, in the shoe industry, and it is also used for finish coat acoustic musical instruments made of wood.

The connection between shellac and the cosmetics industry

In 2010, a novelty appeared on the market of the nail industry, which became truly revolutionary. The American company CND (Creative Nail Design) has introduced a hybrid of nail polish and modeling gel called Shellac. This product incorporates the best properties of lacquers (simple and quick application, the richest palette of colors, bright shine) and gels (stable nail coverage for up to three weeks while maintaining color, no smell). At the same time, it is worth noting such an important point: in contrast to the correction using conventional gels for nails, when removing gel polish, there is no need to cut the material, which means that the natural nail plate is also preserved.

In Russia and the CIS countries, the new invention was dubbed "shellac"(other spellings are shellac, shellac, shellac, and even that - shea varnish), and often they call it not only Shellac itself from CND, but also gel polishes from other manufacturers, of which there are now a huge number. Almost every company that produces products for nails has gel polishes in its catalog. And they all have their own names. But in our country they stubbornly continue to call them "shellacs". Why? For the same reason we call diapers diapers (after their most famous brand, Pampers), and photocopiers, copiers (after the first manufacturer of Xerox copiers). So, shellac is the name of a specific product - gel polish CND Shellac™, which has become a household name in the CIS, where it refers to any gel nail polishes of various brands.

Why do girls need shellac?

Shellac is a special nail coating that combines the properties of conventional varnish and gel, which makes it possible to make a manicure more durable and durable. The bottle with this tool is very similar to the usual varnish and is equipped with the same brush. However, the technique of applying shellac is significantly different from the usual one. Firstly, to create a high-quality manicure, you need four products with different compositions: basic, degreasing, color and fixing. Secondly, you need to properly treat the nail, and thirdly, all formulations must be applied correctly and each of them dried with a special UV lamp. After carrying out such a procedure, shellac on the nails looks beautiful and does not lose its decorative properties about two, and sometimes even those weeks.

The advantages of shellac

• Undoubtedly, the main advantage of shellac is the creation of a durable and durable coating that cannot be erased without special tools. In addition, it does not scratch or chip, and it can only be damaged by rough physical impact.
• According to the assurances of the creators of this tool, its regular use does not harm the nails. This is explained by the fact that in the composition of shellac, in contrast to conventional varnishes, do not contain formaldehyde, toluene and others harmful substances. This gives the tool another advantage - it can be safely applied by pregnant women and even people suffering from allergies.
• Shellac coating creates a strong film on the nail plate, which protects the structure of the nail well and prevents it from exfoliating and cracking. This greatly facilitates the growth of long nails.
• Shellac has a fairly large palette of colors and allows you to create a variety of patterns and patterns on your nails.
• To remove shellac from nails, you do not need to visit the salon and cut off the coating with a nail file. To do this, it is enough to purchase a special tool.

Cons of shellac

• There is no need to hope that shellac will significantly improve the condition of the nails, because, first of all, it is decorative means and not a medicinal product.
• Shellac is more convenient to apply in salons: without an ultraviolet lamp, it simply will not harden. You can, of course, purchase an ultraviolet lamp and all the materials necessary for a Shellac manicure, but it will not be cheap: you will have to pay at least 7 thousand rubles for everything together.
• To remove shellac, it is advisable to use special means and special devices, so it should be removed again in the cabin. Yes, and changing the color of the nail coating for lovers of diversity will cost a pretty penny. However, for those who like to repaint their nails daily, shellac may not be needed at all.
• Shellac is not for everyone! As practice shows, it is not suitable for all nails. On thin, weakened nails and on hands that are daily in water or work on a computer, it may not last even a week.
• Overgrown shellac on the nails looks ugly, so even if the coating is in good condition, it will have to be adjusted. This, for sure, will not be very convenient for those who have fast growing nails.
• Shellac is not particularly resistant to temperature extremes. When nail plates under the influence of moisture and heat, they expand, and then narrow again in a normal environment, restoring their natural shape, micro cracks form on the coating, which are not visually noticeable, but are able to let water and dirt in. Subsequently, under shellac is created good environment for the development of bacteria that can lead to fungus and other nail problems.

Video

Most natural resins are the final stage of the gradual transformation of balms, which occurs under the influence of atmospheric oxygen, sun exposure, moisture, oxidation and polymerization. Under certain conditions, it is possible to obtain resins from balms by distillation. Resins are transparent, sometimes cloudy, colored yellow and Brown color substances that are amorphous, vitreous, softening and melting when heated. A characteristic feature of resins is their insolubility in water, while in organic solvents they either dissolve or swell. They consist of various organic substances, the most important of which are:

Resin acids, for example, abietic and pimaric acids (C 20 H 30 O 2) found in rosin and other resins, succinic acid (C 4 H 6 O 4) contained in amber. Free resin acids are the cause of the acidity of resins.

Resenes, high molecular weight hydrocarbons, are resistant to chemicals. Despite this, they are not the true reason for the resistance of resins, for a very resistant and durable resin - Zanzibar copal contains the same amount of resen (10%) as rosin, which belongs to the least resistant resins, and not very resistant dammara contains 60% resen.

When boiled with alkalis, the resins turn into brown-colored salts of resin acids - semi-solid, even solid, sticky soaps, the so-called resinates, which are used together with aluminum sulfate when sizing paper;

in addition, they are used in the manufacture of soap from fats; resinates increase soap lather. Resinates of lead, cobalt and manganese are currently used as driers.

By origin and method of extraction, we divide resins into those obtained from currently growing trees and fossils - from long-dead trees.

Resins obtained from currently growing trees - mastic, dammara, sandarak and soft copals flow from the cut bark of trees and thicken in air into drops, sticks and “tears” of a characteristic shape. Rosin is extracted from liquid balsam by distillation or extraction from crushed wood.

Shellac, which is a product of animal origin, has a completely different character.

Fossil resins - copals and amber, formed in bygone times, fell into the earth's crust, from where they are mined. Amber is found on the surface in alluvial layers.

By hardness, we divide resins into two groups:

Soft resins, which include most of the resins obtained from currently growing trees - rosin, mastic, dammar, sandarak, shellac, soft copals (manila).

Hard resins - amber, fossil copals and some varieties of copals obtained from trees now growing.

The resistance of soft resins is low. They do not sufficiently resist atmospheric influences, especially air humidity, and undergo autoxidation; their decomposition is accelerated by the ultraviolet part of the light rays. Some types of resins are not affected by ultraviolet rays, while others turn yellow under their influence. Shellac is the most resistant to moisture; in the light, the color of the dammara almost does not change.

The resistance of hard resins is incomparably greater, but we are unable to fully use this property for the preparation of varnishes, since solid resins are very poorly soluble. Resins are superior in light resistance to hardening oils; when aging, compared with oils, they turn yellow, turn brown and darken much less.

Resin solubility. Soft resins dissolve in organic solvents at normal temperatures. Mastic, dammar and rosin dissolve in turpentine; shellac, sandarac and soft manila resins - in alcohol. The easy solubility of dammara and mastic in various solvents is their important advantage in the conservation of paintings, since varnishes, which dissolve easily, can later be washed off without fear of destroying the painting. In contrast, varnishes made from soft resins, soluble only in alcohol, may subsequently cause the destruction of paintings when these varnishes are removed with ethyl alcohol.

By solubility, resins can be roughly divided into the following groups:

Solid resins either do not dissolve at all, or dissolve partially; for the most part they only swell in solvents. If, nevertheless, it is possible to dissolve some resins by many months of exposure to the solvent, then subsequently, during the drying of the varnish film, they fall out in the form of a dull, cloudy porous (spongy) mass. For this reason, resin varnishes with an easily evaporating solvent are not made from solid resins: they are processed mainly in oil varnishes after heat treatment at high temperature. In this case, partial decomposition of the resin is observed, as a result of which solid resins are colored in dark color and partially lose their valuable properties acquired by them during a long stay in the ground. However, after heat treatment, the resins become softer, more soluble and darker in color.

Fluidity temperature. Resins are thermoplastic, amorphous substances; when heated, they gradually soften and eventually become fluid. The transition to the fluid state of resins is not determined by one point on the temperature scale, but varies within a few degrees Celsius. Soft resins soften at the following temperatures:

Hard resins soften at much higher temperatures (190-300°). For these resins, the transition to a fluid state is shifted beyond the limit at which their decomposition begins. Therefore, the softening of resins that are subject to dissolution in oil is associated with their partial destruction.

The degree of hardness of resins is determined by the ambient temperature. In the cold, resins have the greatest hardness and the least elasticity; with increasing temperature, the hardness of the resins decreases, but their elasticity increases.

Resin elasticity is low. They are as fragile as glass and must be made more resilient by the addition of balms and raw natural or polymerized oils. Modern plasticizers for technical varnishes - esters of phthalic, adipic and phosphoric acids - are not suitable for artistic purposes.

Resin acids react with basic pigments, such as zinc, silica and titanium white, to form salts. This is accompanied by an increase in the viscosity of the resin lacquer or precipitation of the resin. Therefore, resins intended to be mixed with pigments are partially neutralized with basic substances (calcium hydroxide, zinc oxide) or esterified. In both cases, the acid number is significantly reduced.

Resins have a high refractive index of light. Moreover, the refractive indices of light of various resins are not very different from each other and fluctuate within 1.515-1.540. Resins also give paints greater depth and darker tint than all other binders, be it oil ( P= 1.48-1.49), wax ( P=1.48) or water-soluble adhesives, gums and starches with a refractive index below 1.45.

Rosin is one of the most common and cheapest types of resin. Rosin is a solid residue obtained by distillation of turpentine balsam extracted from different types pines. By type of pine, we distinguish individual varieties of rosin: French from maritime pine (Pinusmaritima), Russian from Siberian pine (Pinussiberica), American from swamp pine (Pinuspallustris), German from common pine (Pinussilvestris), Austrian from black pine (Pinusfaricio), Indian from Pinuslongifolia, Australian from Pinuslarix.

Rosin contains 90% free resin acids and a small amount of rezenes and resinols. These acids - abietic and pimaric, similar in composition, have two unsaturated bonds and therefore oxidize in air. This is manifested in the fact that the rosin becomes less soluble and turns brown as a result of aging. The main component of French rosin (acid number 140-150) is pimaric acid, American rosin (acid number 160-175) is abietic acid. Consequently, rosin differs not only in origin, but also in composition.

Rosin is an amorphous, brittle, glassy substance that ranges in color from yellow to brown. It melts at 80-120°. Rosin dissolves well in turpentine oil, alcohol and other solvents. Cheap varnishes (not suitable for painting due to their low durability), mastics and glues are made from rosin. Rosin is added to more expensive resins - shellac, dammaru, sandarak, and it reduces their quality. A small percentage of rosin is a necessary additive in the manufacture of oil copal varnishes, since it (rosin) facilitates the melting of hard resins. Rosin is also added to dammar varnishes with an evaporating solvent, as it eliminates the milky haze formed by dammar wax.

The main disadvantages of rosin are, first of all, its too much fragility and softness, and then its low moisture resistance. The lacquer film, initially transparent and shiny, quickly becomes cloudy, turns yellow and even turns brown and gradually turns into powder. Due to the high acid number, rosin varnishes thicken or precipitate when in contact with basic pigments (for example, zinc, titanium and lead white). Pigments that are unstable in an acidic environment (ultramarine) can completely change.

Because of these properties, rosin was considered a low-value waste, which was obtained by distilling turpentine oil. Modern methods, mainly by esterification and curing, rosin ennobles and somewhat improves its properties, therefore, at present, it is a widely used raw material for the manufacture of technical varnishes.

Hardened rosin is obtained from natural rosin by neutralizing resin acids with calcium hydroxide in the form of a fine powder. To 100 parts of molten rosin, 9 parts of powdered calcium hydroxide are added in portions, and the mixture is heated until all the lime is dissolved. Hardened rosin is also obtained by melting natural rosin with zinc oxide or dissolving it in lacquer gasoline and heating the solution with calcium oxide hydrate. By this last method of production, a sufficiently light-coloured rosin is obtained. Cured rosin is an almost neutral, harder product that resists moisture better and does not react with basic pigments.

Esterified rosin is made by esterifying resin acids with glycerol. Molten rosin is mixed with ten or more percent of glycerol and after a few hours heated to 290 °. At the end of the reaction, the acid number drops to 5-8. The resulting ester is more resilient, hard and durable than natural rosin. It dissolves in hydrocarbons, turpentine, benzene, and fully saturated does not dissolve in alcohol.

Both varieties of rosin - esterified and hardened - give with wood oil or with polymerized oils, oil varnishes that resist weathering quite well. Currently, in the manufacture of technical varnishes, they satisfy a significant part of the need for resinous raw materials.

Resinates * zinc, made from rosin, are added to oil varnishes and paints. This contributes to the curing of the varnish throughout the entire thickness of the layer and prevents wrinkling of the surface of the varnish film. Cobalt resinates are the most commonly used modern driers.

Mastic flows from the bark shrub plant Pistacialentiscus, which grows on the Mediterranean coast. The resin obtained from the island of Chios is considered the best. Mastic from other Mediterranean islands is not as valuable. The resins brought from Bombay and South America, although similar to mastic, are also less valuable.

The mastic bush spontaneously secretes a balsam from its bark, which, after three weeks, hardens in air into an elastic resin of fragrant smell and pleasant taste. Mastic is also distinguished from other resins by the fact that it can be chewed like chewing gum, while other resins crumble. Mastic differs from dammara in that it dissolves well in ethyl alcohol and acetone, but does not dissolve in kerosene. Only part of the resin dissolves in petroleum ether. Mastic softens at 99°C and completely melts at 95-110°C. Turns yellow and orange as it ages. In this regard, mastic is less valuable than dammara, which is more lightfast. Significant initial elasticity of fresh mastic, which contains 1-3% essential oils, falls rapidly; mastic gradually becomes more and more brittle, and under the influence of moisture becomes cloudy and, finally, disintegrates into dust. According to my observations, a film of mastic varnish with the addition of 3% castor oil, applied to the primer with lead white, after a year turned yellow, like copal oil varnish. In addition, under the influence of atmospheric influences, the mastic lacquer became completely cloudy after a few months, while the film of copal lacquer did not collapse and remained transparent.

Mastic has long been a favorite resin for making painterly varnishes. We are currently replacing it with dammara. In its pure form, it is fragile as a picturesque varnish, and therefore it is necessary to increase its strength and elasticity by adding 10-30% wax or 5-15% polymerized oil **.

Dammara is brought from Malaya, the Sunda Islands and India. It flows from trees and plants - St. John's wort and araucaria. Dammara goes on sale in the form of transparent, shapeless pieces with a mealy surface. The worst grade is dammar dust, which contains a large amount of contaminants of mineral and organic origin. Dammara is a colorless or slightly yellowish resin, vitreous when fractured. It is softer than gypsum and slightly harder than rosin. It softens at 85-120°C, contains 23% dammarolic acid, 40% alpha-dammar-resen, which is soluble in ethyl alcohol, and 22% beta-dammar-resen, insoluble in ethyl alcohol. Its acid number is 16-35. Dammar dissolves in turpentine oil and in most hydrocarbons, but only partially in alcohol. On this basis, dammaru can be easily distinguished from rosin and manila, soft copals, which dissolve in alcohol without residue.

Of all the properties of dammara, the most important for painting is undoubtedly its great light fastness: when aging, it does not turn yellow at all or turns yellow only slightly, which surpasses all other soft resins. Therefore, it is the most widely used raw material for the manufacture of pictorial varnishes and binders.

When dissolved in turpentine, dammar gives a very shiny, transparent and completely colorless film, which, however, is not moisture resistant enough and becomes cloudy after a short time from atmospheric exposure. In a humid environment, the dammar film turns white and becomes completely opaque. Despite some valuable properties of dammara, such as light resistance and good solubility, one cannot ignore the above disadvantage and neglect it. Oil glazes containing significant amounts of some soft resins gradually turn gray and lose depth and intensity of tone (sometimes after several years). As a consequence, the acceptability of glazes with soft resins is problematic. The use of soft resins, soluble only in turpentine, as varnishes for glazes and top varnishes, on the recommendation of the famous technologist Max Derner, is the greatest mistake made in the technique of painting in recent decades. The Pettenkofer regeneration method, which seems to correct the shortcomings of soft resins, has proved unsatisfactory: the results achieved by this method are quickly lost, and the regeneration of cloudy varnishes has to be repeated at increasingly shorter intervals.

Greater durability and strength are given to soft resins, and hence to dammar, wax additives or hardening oils. Recall that technical varnishes intended for exterior coatings and exposed to weathering contain about 60% oil; while "internal" varnishes, that is, varnishes for indoor coatings, contain only 30% oil, and this amount ensures their strength. However, such varnishes are not suitable for varnishing pictures, since the action of the desiccant oils contained in these varnishes in large quantities causes yellowing and browning of the film, and, moreover, they are very difficult to dissolve and wash off. For painting, we must choose the least yellowing grade of hardening oil; such is the polymerized linseed oil used in painting. Of all the oils, its film retains its elasticity the longest and is the most moisture resistant. The ratio between resin and oil should be kept within the limits that ensure easy solubility (washability) of the varnish, therefore, a maximum of 10-15% oil. There is no need to limit the amount of added wax, as it is quite stable and dissolves easily.

Shellac. Unlike other resins, shellac does not flow from the cut bark of trees, but is a metabolic product of the insect Tachardialacca. Sprigs of the Indian fig tree, covered with shellac a few millimeters thick, are broken off and processed into raw shellac, which, in addition to aleuritic, dihydroxyphycoceryl and shellolic acids, also contains shellac wax (up to 5%), water (2% or more), pollutants ( up to 9%) and water-soluble dye (5%). Raw shellac is crushed, washed with water to remove the dissolving dye. It is then melted, applied to a shaft on which it hardens, and finally it is scraped off in the form of thin flakes. In addition to this brown flake shellac, button shellac is also sold, formed by curing drops of molten resin, and ruby ​​shellac, a less valuable residue in the production of flake shellac.

36 parts white shellac

11 parts crystallized borax

150 parts of boiling water.

In turpentine oil, shellac dissolves by 15%, in benzene - 20%, chloroform - 40%; dissolves completely in alcohol and, after evaporation of the alcohol, gives a hard, shiny and durable lacquer film, a well-known furniture polish. Shellac varnishes are among the most durable alcohol varnishes.

Bleached shellac is obtained from brown resin, which is dissolved in a two percent solution of soda in water. This tar-soda solution is then bleached with bleach; after bleaching, the resin is isolated with acid, washed in water, and shellac gloss sticks are formed. This grade of shellac loses its ability to dissolve in alcohol in air, and therefore it should be stored under water, although even then, after long storage, its ability to dissolve is reduced by residual bleaching substances. If the bleaching agents are carefully removed, the solubility of shellac does not decrease. (The solubility of old shellac can be improved by first allowing it to swell in a small amount of ether and only after that ethyl alcohol is added.) Bleached shellac is more brittle than flake shellac and contains up to 15% water, which must be removed from the crushed shellac before making varnish. resin by heating. The elasticity of rather fragile shellac varnishes can be increased by adding 3% - maximum 5% castor oil or 5% Venetian turpentine. Other oil emollients are unsuitable for this purpose, since they do not dissolve in alcohol.

Shellac varnishes are superior in moisture resistance to varnishes made from dammara, mastic and soft manila copals. Most often, furniture polishes are made from shellac varnishes, sometimes charcoal drawings are fixed with a two-three percent solution of shellac (which, however, gradually turn yellow), and, finally, they are used to isolate absorbent chalk soils for painting. as a varnish for oil painting they are completely unsuitable, since alcohol, which is an excellent solvent of linoxin 13, contributes to the swelling of slightly dried oil paint. In addition, shellac varnishes dry out too quickly and, when set, cannot create an even layer. Shellac, perhaps, could be varnished on tempera, which dries to form a hard layer and is written on a hard base; however, dammara and wax lacquer is most suitable for tempera, which does not turn yellow and can be easily removed.

Sandarac stems from the coniferous trees of Callitris quadrivalvis growing in the Mediterranean region, in northern Africa and in Australia. It goes on sale as Madagascar or Alexandrian sandarak in the form of small yellow pieces. oval shape or in the form of sticks. Sandarak is fragile; melts at 135-150°C and is readily soluble in alcohol, while it is only partially soluble in turpentine oil. Alcohol varnish from sandarak gives a shiny, brittle film that is harder than that of mastic and dammara; however, the film turns red as it ages. To reduce its high fragility, a small amount of Venetian balsam, castor oil or elemi is added to the alcohol solution. When benzene is added, in which it dissolves only partially, sandarak gives a varnish that dries to form matte surface. As a result of boiling sandarak with oil, we get quite strong oil varnishes, but they are painted orange or brown.

Characteristic indicators for soft resins

Amber is the resin of extinct coniferous trees that grew in the Tertiary period on the coast of the Baltic Sea. It has the appearance of transparent or translucent pieces of yellow or brown-red color. Conchoidal fracture, resinous luster. Amber contains mainly esters of succinic acid, but also other acids. It melts at 300-375°C. The refractive index is P= 1.546. The most valuable varieties - transparent and light yellow - are sold under the name succinite. Amber does not completely dissolve in any of the known solvents; it partially dissolves only in alcohol, acetone, benzene and ether. To make varnishes from it, you must first melt it, while it partially decomposes (by dry distillation) and at the same time loses 20-30% in weight. Fused amber, the so-called amber rosin, is a brown resin that is softer and more brittle than the original amber. It dissolves in turpentine oil, alcohol, and, at elevated temperatures, in hardening oils. Amber varnishes on volatile solvents are colored brown-red, even dark brown. After removing the solvent, a brittle film remains. Oily amber varnishes, also dark-colored, but they have significant weather resistance. Currently, however, they are not produced, and lighter copal or synthetic varnishes are sold under the name of amber varnishes.

We distinguish amber resin from other hard resins by the fact that it does not dissolve in cajeput oil, in which hard copals dissolve. Amber differs from artificial phenolic resins in its refractive index. By pressing amber waste at elevated temperature, a homogeneous ambroide is obtained, which has a more matte luster than real amber.

Kopals. The common name "copal" refers to a large number various resins, differing in origin and properties. We divide them into two main groups: soft and hard.

Soft copals (also called fake) manila, Indian and kauri, have a hardness not exceeding the hardness of soft resins - dammar, mastic and rosin. Of these, quick-drying alcohol and turpentine varnishes of poor quality are made.

Hard copals (also called real copals) are found at a depth of several tens of centimeters to 1 meter in sandy soil in the form of the remains of trees that once grew. These are resins, fossil or semi-fossil, which, as a result of a long stay in the earth, have acquired their characteristic properties: hardness, high melting point and insolubility in organic solvents.

The hardest varieties are sold as Zantzibar copals, but they are also found in other remote places in Africa. They are pieces of various shapes and sizes with an opaque crust, which is removed at the place of extraction. They are amorphous, have a resinous sheen, conchoidal fracture and a rough surface, the so-called "goosebumps". Most often they are yellow, like amber, which they look like not only appearance, but also a property, so they are often passed off as amber.

In addition to fossil varieties, there are also semi-fossil Zanzibar copals, located underground near living trees. Other, fresh resin varieties are extracted directly from the copal tree (Trachylobium verrucosum).

In total, about seventy varieties of Zanzibar copal are known. There are a huge number of all copal resins; they differ only in origin. More detailed data regarding the origin and properties are not given. Before going on sale, the upper opaque layer is removed from the copals mechanically - by scraping or washing in a two percent soda solution. Copals are distributed according to variety, color and size; they are supplied to paint and varnish factories of a certain established quality.

The hardest are East African kopals: Zanzibar, Madagascar and Mozambique. Of the West African copals, the best known are Congo copals, fossil varieties of which are the main, most suitable raw material for the manufacture of hard oil varnishes. Fresh copals are harvested from the Copaifera Demensi tree, native to the Belgian Congo. This group also includes copals - Angolan, Benguela, Gaboon, Cameroonian, semi-solid Benin and fresh Sierra Leone from the Copaiferaguibourtiana tree, giving light, elastic and durable varnishes. The hard Australian resins, marketed as kauri copals, come from Agathisaustralis trees. They melt easily and with oil give a varnish, the film of which does not swell in water. Indian hard copals - Manila are known as agathocopales; some of them come from the Agathisalba tree. Other resins imported under this name from the Philippines are softer than other resins. South American copals, of which the Brazilian, Colombian and Venezuelan varieties are best known, are almost never found in European markets.

All of the listed hard copals are difficult to dissolve. Hard copals can be distinguished from soft copals and soft resins by the fact that they do not change even after half an hour of boiling in water (soft resins become cloudy). Bottler ranked them in order of hardness, from hardest to softest, in the following order: Zanzibar, Mozambique, Angolan Red, Sierra Leone, Flint, Benguela Yellow, Benguela White, Cameroonian, Congo, Manila Hard, Angolan White and kauri.

Hard copals dissolve only partially and very differently in alcohol, turpentine oil, chloroform and other organic solvents. So, for example, Zanzibar copal does not dissolve in turpentine oil, while Madagascar copal, which is very close in hardness to it, dissolves in it by 40%. The solubility of the copals can be slightly increased by heating at 100° for 48 hours, after which they should be immediately crushed and placed in a solvent. The dissolution process can be accelerated in another way, namely by exposing the pulverized resin in a thin layer to air for a long time. AT recent times it was possible to completely dissolve some varieties of copals in newly discovered very effective solvents - ketones.

Volatile copal lacquers, which, however, we are not able to produce of satisfactory quality, are, so to speak, of no importance in comparison with oil copal lacquers, which until recently were the best in durability, strength and hardness. The fluidity temperature of copals varies depending on the type of resin within 150-360 ° C. When heated, copals, like amber, partially decompose, and the weight of the resin decreases by 20-25 % . The softened resin, the so-called copal rosin, dissolves both in organic solvents and at elevated temperatures in hardening oils. Different heat resistance of individual varieties of copal affects the quality of the oil varnish. The hardest oil varnishes are made from Congo and cowrie copals; although these resins are softer than East African copals, they are less degradable when softened. Copal softening can be facilitated both by heating for several days at 200°C, and by adding small pieces of rosin covering the bottom of the boiler in which the copal is heat treated. According to Bottler's data, copals melt at the following temperatures: angola red copal - 305 °, Zanzibar copal - 269 °, lindi - 246 °, white angola copal - 245 °, flint - 220 °. Sierra Leone - 185 °, Benguela white - 175 °, Benguela yellow - 170 °, Cameroon - 160 °, Manila hard - 135 °. Softening temperatures may deviate somewhat from the figures given, since copals of the same variety often have slightly different composition and properties.

Copals are esterified. The acid number of copals, as well as rosin, can be significantly reduced by esterification, that is, by fusing the resin with 6% glycerol. When heated, glycerin combines with free butyric acids of copal, forming neutral esters, and the acid number of copal drops to 8-12, and the specific gravity increases. Copal esters are soluble in most organic solvents, with the exception of ethyl alcohol. They also dissolve much easier in hot oil, which no longer needs to be heated to high temperature needed to dissolve natural copals. For this reason, ethercopal varnishes are lighter in color.

Esterified copals are also used in combination with artificial resins and cellulose derivatives. In artistic painting, they have not been used to date.

The name "copal" resins is derived from the Aztec word Kopalli. The original name anime, which was already used in antiquity and by which completely different resins (gummianime) are currently designated, we find in recipes of the 17th and 18th centuries. In the old days, kopals were quite often confused with amber.

In the Middle Ages, the Arabs traded copal. In the XVIII and XIX centuries copals were highly valued, as the most durable varnishes were made from them. The name "carriage lacquer", which was meant to express resistance to rain, sun and frost, has survived to this day as a trade name for valuable solid oil lacquers.

In earlier times, and even as far back as the 19th century, copal varnishes were made from hard, refractory fossil resins - Zanzibar copal and similar varieties. At the end of the 19th century, fossil New Zealand kauri resins, which softened at a lower temperature than East Indian resins, took advantage. The locations of these resins were, however, soon exhausted, and at the beginning of our century, during the period when the Belgians occupied the Congo, they began to extract copal congo on a vast territory. This resin then became the main raw material for the most valuable oil varnishes.

Recently, the importance of fossil resins has fallen due to the exhaustion of their reserves, and mainly due to the organization of the production of quick-drying varnishes from artificial resins and cellulose derivatives.

Characteristic indicators for solid resins

Artificial copals are modified artificial phenol-formaldehyde, acrylic and other resins, combined with oil into resistant technical varnishes. They differ significantly from natural copals in their chemical composition. They go on sale under different trade names, of which the most famous are: pergomoles, bekacites, abifenes and albertols. (See the chapter on artificial resins.)

* The acids that make up rosin form salts with metal ions - resinates.

** Rosin falsification test according to Storch and Moravsky: mastic contaminated with rosin, dissolved in acetic anhydride, turns red when sulfuric acid is added (author's note).

Shellac is an organic substance of natural origin, the secretion of Lacquer bugs that live on some types of trees in Southeast Asia and India. Shellac is secreted by insects to protect their bodies, they drink the sap of the tree and process it into varnish resin. The female lays her eggs in a resin nest, in which the larva then develops. Having got out of the nest, the larva settles nearby on a branch and begins to actively drink the juice, covering its body with lacquer resin, the layer of which becomes thicker and almost completely covers the insect. An insect develops from an egg to an adult in about 6 months, so shellac is harvested twice a year, leaving part of the population on the branches for reproduction.

Harvesting consists of scraping off the resin from the branches. Then the resin is dried, washed, cleaned. For the final cleaning, shellac is melted in canvas bags: the resin seeps through the fabric, leaving all the debris inside the bag. The molten resin is poured into molds to form a vitreous mass. For sale, shellac is produced in the form of scales, thin plates, vitreous fragments, tablets (“buttons”).

Properties

Shellac consists of organic fatty acids, a water-soluble dye, water and shellac wax (up to 15%). It dissolves well in alcohols (methyl, ethyl), alkalis and their solutions, but very poorly in gasoline, fats and oils.

Compound, physical properties and color of shellac depend on harvest time and cleaning methods. The most expensive is bleached shellac and lightly cleaned of wax. yellow color. The shellac varnish cleared of wax differs in good water resistance. The color of shellac can vary from pale yellow (discolored) to dark brown, almost black, with a reddish tinge.

Shellac does not conduct current, conducts heat poorly, melts at a temperature of 80 to 120 ° C, softens at a temperature of about +65 ° C.

For application, dry shellac is dissolved in alcohol. Shellac lacquer goes on sale in dry form or in the form of a ready-made concentrated solution, which should then be diluted to the desired consistency. In our store chemicals you can buy high-quality technical shellac varnish in the form of a bulk mass.

Dry shellac can be stored for a long time at room temperature, without sudden changes in temperature and humidity, and without access to sunlight. Liquid shellac varnish can be stored for no more than 1 year, preferably no more than 6 months.

The finished shellac lacquer gives a thin lacquer coating that is well polished to a glossy sheen. The coating is quite plastic, durable, under mechanical influences on the tree, it does not chip off the surface, but bends along with the board. Shellac lacquer is characterized by high adhesion (adhesion) to any surfaces, both porous and very smooth. Lacquer is applied in several layers, as the first layer is absorbed into the wood.

Shellac is edible and completely non-toxic.

Application

- The most common use of shellac is as a varnish and polish for furniture. It is believed that shellac lacquer best emphasizes the beauty of valuable wood, so it is used in the restoration and repair of antique and antique furniture, caskets. Before the invention of synthetic lacquers, shellac lacquer was the most common furniture finishing material used as a polish and primer. Shellac wood dye has been known since 250 AD.
- Lacquer shellac is used to cover the wooden cases of the most expensive musical instruments.
- Shellac is also used to prepare the surface for gold leaf and sometimes to set the gold finish. In India - for varnishing and finishing decorative items (beads, bracelets).
- Discolored shellac varnish is used to protect paintings and icons. The advantages of this method include its reversibility. The varnish can be easily removed from the painting if necessary.
- Included in some varieties of drying oil, rubber, sealing wax.
- Based on it, insulating materials for the electrical industry are produced.
- In the food industry and pharmaceuticals - glazing agent for sweets, chocolate, dragees, chewing gums, fresh fruits, nuts, coffee beans, flour products, tablets (additive E-904).
- In photography.
- Until the middle of the 20th century, when vinyl was invented, shellac was part of the mass from which records for gramophones were made.
- Shellac is an ingredient in pyrotechnic colored charges, such as flares (green), tracers and bullets.

The store of chemical reagents in Moscow and the region "PrimeChemicalsGroup" offers to buy both shellac and other substances and materials, including those of organic origin. We sell BAU activated carbon, potato starch, sucrose, alkali and much more - the range is very wide, and the prices are more than affordable.