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

During the swarming period, scale insects sit on tree branches and absorb tree sap, digest it and secrete a resinous substance. The varnish crust is collected in June and November. Afterwards it is crushed, washed and dried 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 melted varnish is pressed through the canvas, after which it is melted again and cast into rectangular shapes. 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 flammable substance, for example, for signal lights.
• Shellac is edible and is used as a glaze to coat tablets, candies and other things (referred to in the composition as food supplement E-904).
• Alcohol-based shellac varnish is used in the furniture industry, in the shoe industry, and it is also used for finishing coating acoustic musical instruments made of wood.

The connection between shellac and the cosmetics industry

In 2010, a new product appeared on the nail industry market that became truly revolutionary. The American company CND (Creative Nail Design) introduced a hybrid of nail polish and modeling gel called Shellac. This product incorporates the best properties of varnishes (simple and quick application, a rich palette of colors, bright shine) and gels (stable nail coating for up to three weeks while maintaining color, no odor). It is worth noting this important point: in contrast to correction using regular gels for nails, when removing gel polish there is no need to file the material, which means the natural nail plate is preserved.

In Russia and the CIS countries the new invention was dubbed "shellac"(other spellings are shellac, shellac, shilak, and even Shilac), and this is often called not only by Shellac itself from CND, but also by gel polishes from other manufacturers, of which there are now a huge number. Almost every company that produces nail products 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 why we call diapers diapers (in honor of their most famous brand, Pampers), and copiers, copiers (after the first manufacturer of copiers, Xerox). So, shellac is the name of a specific product - CND Shellac™ gel polish, 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 coating for nails that combines the properties of regular varnish and gel, allowing you to make your manicure more durable and long-lasting. The bottle with this product 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: base, degreasing, color and fixing. Secondly, you need to properly treat the nail, and thirdly, all compounds must be applied correctly and each of them must be dried using a special UV lamp. After this procedure, shellac on the nails looks beautiful and does not lose its properties. decorative properties about two, and sometimes even that weeks.

Pros of shellac

• Undoubtedly, the main advantage of shellac is the creation of a durable and durable coating that cannot be erased without special products. In addition, it does not scratch or chip, and it can only be damaged by rough physical force.
• According to the creators of this product, its regular use does not harm the nails. This is explained by the fact that shellac, unlike regular varnishes, does not contain formaldehyde, toluene and others harmful substances. This gives the product another advantage - it can be used without fear by pregnant women and even people suffering from allergies.
• Shellac coating creates a durable film on the nail plate that well protects the structure of the nail and prevents it from peeling and cracking. This makes it much easier to grow long nails.
• Shellac has a fairly large palette of colors and allows you to create a variety of designs and patterns on your nails.
• To remove shellac from your nails, you don’t need to visit a salon and file the coating off 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 your nails, because, first of all, it is decorative means, and not a medicinal drug.
• It is more convenient to apply shellac in salons: without an ultraviolet lamp it simply will not harden. You can, of course, buy an ultraviolet lamp and all the materials necessary for a Shellac manicure, but it won’t be cheap: you’ll 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. And for those who love variety, changing the color of their nails will cost a pretty penny. However, those who like to repaint their nails every day may not need shellac 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 in water every day or work on a computer, it may not last even a week.
• Overgrown shellac on nails looks unsightly, so even if the coating is in good condition, it will have to be adjusted. This will probably not be very convenient for those whose nails grow quickly.
• Shellac is not particularly resistant to temperature changes. When nail plates under the influence of moisture and heat they expand, and then in a normal environment they contract again, restoring their natural shape; micro cracks form on the coating, not visually noticeable, but capable of allowing water and dirt to enter. Subsequently, under shellac it 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, solar exposure, moisture, oxidation and polymerization. Under certain conditions, it is possible to obtain resins from balsams by distillation. The resins are transparent, sometimes cloudy, colored yellow and Brown color substances that are amorphous, glassy, ​​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 cause acidity in resins.

Rezenes, hydrocarbons of high molecular weight, are resistant to chemical reagents. Despite this, they are not the true reason for the durability of resins, because a very resistant and durable resin, Zanzibar copal, contains the same amount of resin (10%) as rosin, which is one of the least resistant resins, and the not very resistant dammara contains 60% resin.

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

in addition, they are used in the production of soap from fats; resinates increase the foaminess of soap. Lead, cobalt and manganese resinates are currently used as driers.

Based on their 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 tree bark and in the air condense 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 long-gone times, fell into the earth's crust, from where they are mined. Amber is found on the surface in sediment layers.

Based on hardness, we divide resins into two groups:

Soft resins, which include most of the resins obtained from currently growing trees - rosin, mastic, dammara, sandarac, shellac, soft copals (Manila).

Solid resins - amber, fossil copals and some varieties of copals obtained from currently growing trees.

The durability of soft resins is low. They do not sufficiently resist atmospheric influences, especially air humidity, and undergo self-oxidation; their decomposition is accelerated by the ultraviolet part of 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 dammara almost does not change.

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

Resin solubility. Soft resins dissolve in organic solvents at normal temperature. Mastic, dammara 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 when preserving paintings, since varnishes that dissolve easily can be washed off later without fear of destroying the painting. In contrast, varnishes made from soft resins that dissolve only in alcohol may subsequently cause destruction of paintings when these varnishes are removed with ethyl alcohol.

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

Solid resins either do not dissolve at all or partially dissolve; for the most part they only swell in solvents. If it is nevertheless possible to dissolve some resins by exposure to a solvent for many months, then subsequently, as the varnish film dries, they fall out in the form of a dull, cloudy porous (spongy) mass. For this reason, resin varnishes with an easily evaporated solvent are not made from solid resins: they are processed mainly into oil varnishes after preliminary heat treatment at high temperature. In this case, partial decomposition of the resin is observed, as a result of which the solid resins are colored 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.

Pour point. 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 fluctuates 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, 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.

The elasticity of resins is low. They are as fragile as glass and must be made more resilient by adding 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, silicon and titanium white, forming salts. This is accompanied by an increase in the viscosity of the resin varnish or resin precipitation. Therefore, resins intended for mixing with pigments are partially neutralized with basic substances (calcium hydroxide, zinc oxide) or esterified. In both cases, the acid number decreases significantly.

Resins have a high refractive index of light. Moreover, the refractive indices of light of different resins are not very different from each other and range from 1.515 to 1.540. Resins also give paints greater depth and darker shade than all other binders, be it oil ( P= 1.48—1.49), wax ( P=1.48) or water-soluble adhesives, gums and starch, the refractive index of which is below 1.45.

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

Rosin contains 90% free resin acids and a small amount of resenes and resinols. These acids, abietic and pimaric, are similar in composition, have two unsaturated bonds and therefore oxidize in air. This manifests itself in the fact that 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, rosins differ from each other not only in origin, but also in composition.

Rosin is an amorphous, brittle, glassy substance ranging 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 adhesives are made from rosin. Rosin is added to more expensive resins - shellac, dammar, sandarac, and it reduces their quality. A small percentage of rosin is a necessary additive in the manufacture of oil copal varnishes, as it (rosin) facilitates the melting of solid resins. Rosin is also added to dammar varnishes with an easily evaporating solvent, as it eliminates the milky haze formed by dammar wax.

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

Because of these properties, rosin was considered a low-value waste product obtained from the distillation of turpentine oil. Modern methods, mainly by esterification and hardening, rosin is refined and its properties are somewhat improved, so at present it is a widely used raw material for the production of technical varnishes.

Cured rosin is obtained from natural rosin by neutralizing resin acids with calcium oxide hydrate in the form of a fine powder. To 100 parts of molten rosin, add 9 parts of powdered calcium oxide hydrate in portions and the mixture is heated until all the lime is dissolved. Cured rosin is also obtained by melting natural rosin with zinc oxide or dissolving it in varnish gasoline and heating the solution with calcium oxide hydrate. This last method of production produces a fairly light rosin. Cured rosin is a nearly neutral, harder product that resists moisture better and does not react with base pigments.

Esterified rosin is produced by esterifying resin acids with glycerol. Molten rosin is mixed with ten or more percent glycerin 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 elastic, hard and durable than natural rosin. It is soluble in hydrocarbons, turpentine, benzene, and when fully saturated it is insoluble in alcohol.

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

Zinc resinates, made from rosin, are added to oil varnishes and paints. This promotes hardening of the varnish over the entire thickness of the layer and prevents the surface of the varnish film from wrinkling. Cobalt resinates are the most commonly used modern driers.

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

The mastic bush spontaneously secretes a balm from its bark, which after three weeks hardens in air into an elastic resin with an aromatic odor 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°. As it ages it turns yellow and orange. In this regard, mastic is less valuable than dammara, which has greater light resistance. Significant initial elasticity of fresh mastic, which contains 1-3% essential oils, falls quickly; mastic gradually becomes more and more brittle, and under the influence of moisture it 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 primer with lead white, after a year it turned yellow, like copal oil varnish. In addition, under the influence of atmospheric influences, the mastic varnish became completely cloudy after a few months, but the film of copal varnish did not collapse and remained transparent.

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

Dammara comes 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 powdery 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, glassy 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-resene, which is soluble in ethyl alcohol, and 22% beta-dammar-resene, insoluble in ethyl alcohol. Its acid number is 16-35. Dammara is soluble in turpentine oil and most hydrocarbons, but only partially soluble in alcohol. By this feature, dammar 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 resistance: when aging, it does not turn yellow at all or turns yellow only slightly, which is superior to all other soft resins. Therefore, it is the most widely used raw material for the production of painting varnishes and binders.

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

Greater durability and strength are imparted to soft resins, and therefore to dammar, by the addition of wax or hardening oils. Let us remember that technical varnishes intended for external coatings and exposed to atmospheric influences contain about 60% oil; while “interior” 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 paintings, since the influence of the oils and drying agents contained in large quantities in these varnishes causes yellowing and browning of the film and, in addition, they dissolve and wash off very poorly. For painting we must choose the least yellowing grade of hardening oil; this is 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 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 wax added, since it is quite stable and easily dissolves.

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

36 parts white shellac,

11 parts crystallized borax,

150 parts boiling water.

Shellac dissolves 15% in turpentine oil, 20% in benzene, 40% in chloroform; It dissolves completely in alcohol and, after the alcohol evaporates, gives a hard, shiny and durable varnish film, a well-known furniture polish. Flake shellac varnishes are among the most durable alcohol varnishes.

Bleached shellac is made 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 formed into sticks of shellac gloss. This type of shellac loses its ability to dissolve in alcohol when exposed to air, and therefore should be stored under water, although even then, after prolonged storage, its ability to dissolve is reduced by residual bleaching agents. If the bleaching agents are carefully removed, the solubility of shellac is not reduced. (The solubility of old shellac can be improved by first allowing it to swell in a small amount of ether and only then adding ethyl alcohol.) Bleached shellac is more brittle than flake shellac and contains up to 15% water, which must be removed from the crushed powder before making the 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 softeners are not suitable for this purpose because 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 to three percent shellac solution (which, however, gradually turn yellow), and, finally, they are used to isolate absorbent chalk soils for painting. As varnishes for oil painting they are completely unsuitable, since alcohol, which is an excellent solvent for linoxin 13, promotes the swelling of slightly dry oil paint. In addition, shellac varnishes dry too quickly and, when they set, cannot create an even layer. Shellac, perhaps, could be used to varnish tempera, which dries to form a hard layer and is written on a solid base; however, even for tempera, the most suitable varnish is made from dammara and wax, which does not turn yellow and can be easily removed.

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

Characteristics for soft resins

Amber is the resin of extinct coniferous trees that grew in the Tertiary period on the Baltic Sea coast. It looks like transparent or translucent pieces of yellow or brown-red color. The fracture is conchoidal, the luster is resinous. Amber contains mainly esters of succinic acid, as well as 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 known solvent; it is partially soluble only in alcohol, acetone, benzene and ether. To make varnishes from it, you must first melt it, during which it partially decomposes (dry distillation) and at the same time loses 20-30% in weight. Fused amber, the so-called amber rosin, is a brown resin, softer and more fragile than the original amber. It dissolves in turpentine oil, alcohol, and at elevated temperatures - in hardening oils. Amber varnishes based on easily evaporating solvents are colored brownish-red, even dark brown. After removing the solvent, a fragile film remains. Oil-based amber varnishes are also dark-colored, but they have significant weather resistance. At present, however, they are not produced, and lighter copal or synthetic varnishes are sold under the name amber varnishes.

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

Kopaly. 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 cowrie have a hardness that does not exceed the hardness of soft resins - dammar, mastic and rosin. They are used to make low-quality, quick-drying alcohol and turpentine varnishes.

Hard copals (also called real ones) are found at a depth of several tens of centimeters to 1 meter in sandy soil in the form of the remains of once-growing trees. These are resins, fossils or semi-fossils, which, as a result of a long stay in the ground, 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 mined in other remote places in Africa. They are pieces of various shapes and sizes with an opaque crust, which is removed at the extraction site. They are amorphous, have a resinous sheen, conchoidal fracture and a rough surface, the so-called “goose bumps”. Most often they are yellow, like amber, which they resemble not only appearance, but also properties, which is why they are often passed off as amber.

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

In total, about seventy varieties of Zanzibar copal are known. There is a huge amount of all copal resins; they differ only in origin. More detailed information regarding origin and properties is not provided. Before going on sale, the top opaque layer of copals is removed 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 factories of a certain established quality.

The hardest are the East African copals: Zanzibar, Madagascar and Mozambique. Of the West African copals, the most famous are the Congo copal, the fossil varieties of which are the main, most suitable raw material for the manufacture of hard oil varnishes. Fresh Congo copals come from the Copaifera Demensi tree, which grows in the Belgian Congo. This group also includes copals - Angolan, Benguela, Gaboon, Cameroon, semi-hard Benin and fresh Sierra Leone from the Copaiferaguibourtiana tree, which produce light, elastic and durable varnishes. The hard Australian resins marketed as kauri copals are obtained from Agathisaustralis trees. They melt easily and, when combined with oil, produce a varnish whose film does not swell in water. Indian hard copals - Manila ones are known as agatocopals; 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 most famous are the Brazilian, Colombian and Venezuelan varieties, are almost never found on European markets.

All of the listed solid 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 boiling for half an hour in water (soft resins become cloudy). Bottler ranked them according to their degree of hardness, from hardest to softest, as follows: Zanzibar, Mozambique, Angolan red, Sierra Leone, flint, Benguela yellow, Benguela white, Cameroon, Congo, Manila hard, Angolan white and cowrie.

Solid copals dissolve only partially and very unequally in alcohol, turpentine oil, chloroform and other organic solvents. For example, Zanzibar copal does not dissolve in turpentine oil, while Madagascar copal, which is very close in hardness, dissolves in it by 40%. The solubility of 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 powdered resin in a thin layer to air for a long time. IN Lately It was possible to completely dissolve some varieties of copals in newly discovered very effective solvents - ketones.

Volatile copal varnishes, which, however, we are unable to produce of satisfactory quality, have, so to speak, no significance in comparison with oil-based copal varnishes, which until recently were the best in durability, strength and hardness. The flow temperature of copals varies depending on the type of resin within 150-360 ° C. When copals, like amber, are heated, partial decomposition occurs, 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. The different heat resistance of individual copal varieties 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 destructible when softened. The softening of copals can be facilitated either by heating for several days at 200°C or by adding small pieces of rosin to cover the bottom of the boiler in which the copals are heat treated. According to Bottler, copals melt at the following temperatures: Angola red copal - 305°, Zanzibar copal - 269°, Lindy - 246°, Angola white copal - 245°, flint copal - 220°. Sierra Leone - 185°, Benguela white - 175°, Benguela yellow - 170°, Cameroon -160°, Manila solid - 135°. Softening temperatures may deviate somewhat from the given values, since copals of the same variety often have slightly different composition and properties.

Esterified copals. 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 more easily in hot oil, which no longer needs to be heated to high temperature, necessary for dissolving natural copals. For this reason, ether-copal varnishes are lighter.

Esterified copals are also used in combination with artificial resins and cellulose derivatives. They have not yet been used in artistic painting.

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

In the Middle Ages, Arabs traded copal. In the XVIII and 19th centuries copals were highly valued, since the most durable varnishes were made from them. The name “carriage varnish,” which was intended to express resistance to rain, sun and frost, has survived to this day as a trade designation for valuable solid oil varnishes.

In earlier times, and even as early 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, fossilized New Zealand cowrie resins, which softened at lower temperatures than East Indian resins, took advantage. The locations of these resins were, however, soon exhausted, and at the beginning of this century, during the period when the Belgians occupied the Congo, Congo copal began to be mined there over a vast area. 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 depletion of their reserves, and mainly due to the organization of the production of quick-drying varnishes from artificial resins and cellulose derivatives.

Characteristics for solid resins

Artificial copals are modified artificial phenol-formaldehyde, acrylic and other resins, combined with oil to form durable 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: pergomols, bekatsites, abifens and albertols. (See chapter on artificial resins.)

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

** Test for adulteration of mastic with rosin 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 lac beetles 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 lacquer resin. The female lays eggs in a resin nest, in which the larva then develops. Having emerged from the nest, the larva settles nearby on a branch and begins to actively drink the juice, covering its body with varnish resin, the layer of which becomes thicker and almost completely covers the insect. An insect develops from egg to adult in about 6 months, so shellac is collected twice a year, leaving part of the population on the branches for reproduction.

Harvesting involves scraping the resin from the branches. Then the resin is dried, washed, and cleaned. For 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 glassy mass. Shellac is produced for sale in the form of flakes, thin plates, glassy fragments, and tablets (“buttons”).

Properties

Shellac consists of organic fatty acids, 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 the color of shellac depend on harvest time and cleaning methods. The most expensive is considered to be bleached shellac and lightly cleared of wax. yellow color. Shellac varnish, cleared of wax, has good water resistance. The color of shellac can vary from pale yellow (discolored) to dark brown, almost black, with a reddish tint.

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

For use, dry shellac is dissolved in alcohol. Shellac varnish is sold 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 chemical reagents You can buy high-quality technical shellac varnish in the form of a loose mass.

Dry shellac can be stored for quite 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.

Ready-made shellac varnish gives a thin varnish coating that is well polished to a glossy shine. The coating is quite plastic, durable, and under mechanical stress on the wood it does not break off the surface, but bends along with the board. Shellac varnish is characterized by high adhesion (adhesion) to any surface, both porous and very smooth. The varnish is applied in several layers, as the first layer is absorbed into the wood.

Shellac is edible and absolutely non-toxic.

Application

- The most common use of shellac is as varnish and polish for furniture. It is believed that shellac varnish best emphasizes the beauty of valuable wood, so it is used in the restoration and repair of ancient and antique furniture and boxes. Before the invention of synthetic varnishes, shellac varnish was the most common material for finishing furniture, used as a polish and primer. Shellac wood dye has been known since 250 AD.
- Shellac varnish is used to coat the wooden bodies of the most expensive musical instruments.
- Shellac is also used to prepare surfaces for gold leaf and sometimes to set gold trim. In India - for varnishing and finishing decorative items(beads, bracelets).
- Bleached 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.
- It is used to produce insulating materials for the electrical industry.
- In the food industry and pharmaceuticals - a glazing agent for sweets, chocolate, dragees, chewing gum, 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 a component of pyrotechnic colored charges, such as signal charges (green), tracers and bullets.

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