Fabric glue: varieties, home recipes, characteristics. Water-soluble adhesive for the food industry Casein adhesive mixture
Legion Company LLC produces water-soluble adhesives for gluing all types of paper labels, excise stamps on glass bottles, jars, PET containers, tin containers on imported and domestic labeling machines
Detailed description:
Legion Company LLC produces water-soluble adhesives for gluing all types of paper labels, excise stamps on glass bottles, jars, PET containers, tin containers on imported and domestic labeling machines.
Qualitative advantages of KLM adhesives:
the dried layer of glue is transparent, which allows you to keep the inscriptions on the back side labels;
the glue has a neutral environment, which ensures corrosion resistance when using glue-applying equipment; there is no reaction with printing inks and metallized coatings;
the adhesive maintains high adhesive strength over a wide range of temperatures and humidity when storing finished products, and is also resistant to icy cold water and condensation on containers due to temperature changes;
is environmentally friendly and can be used in the manufacture of food packaging.
Technological advantages:
short time for fixing the label on the bottle;
the adhesive is intended for use in high-performance labeling machines, as well as for gluing excise stamps on different types of surfaces;
short drying time, which allows you to maintain the fixation of the label during conveyor transport and packaging of finished products;
does not require additional heating during application;
Possibility of application to wet glass containers.
Labeling adhesive KLM-002 is a water-soluble colloidal adhesive based on casein, natural resin and dispersion. For gluing excise stamps. For gluing labels: applique or overlap on both dry warm and wet cold glass containers; application or overlap on both dry warm and wet cold PET containers; overlapped onto tin containers (canned food, paints). Adhesive, can be used for both manual application, and on various types of labeling equipment.
Labeling adhesive KLM-004 is a water-soluble colloidal adhesive based on natural and synthetic polymers.
Labeling adhesive KLM-003 is a water-soluble colloidal adhesive based on modified starches. For gluing labels: on glass hot dry, cold wet containers (canned food, wine, vodka, etc.); application and overlap (more than 8 mm) on PET containers (water, household chemicals, sunflower oil, beverages); overlap onto tin containers (canned food, paints); for paper and cardboard containers; metallized label. The adhesive can be used both for manual application and on various types of labeling equipment at speeds up to 20,000 bottles/hour.
The adhesive composition is intended for gluing cardboard boxes with a varnished surface when packaging quick-frozen products. To prepare the glue, use a mixture of casein solution with active additives with a mass concentration in the range of 28-31.4%, with an alkaline solution of oxidized starch with a mass concentration in the range of 23-24.8%. In this case, the mass ratio of the components is 5:1. The adhesive composition has increased frost resistance and can withstand at least four freezing and thawing cycles.
The invention relates to compositions of water-soluble adhesive compositions for Food Industry, in particular to adhesive compositions intended for gluing cardboard boxes with a varnished surface for packaging frozen foods. A known adhesive composition includes water-soluble cellulose ether, polyethylene oxide, disodium ethylene diamine tetra acetic acid, glycerin, kaolin and water (SU 1175960 08/30/85). The disadvantage of this glue is its relatively low viability and weak adhesion to the varnished surfaces of boxes at low temperatures. Synthetic glue made in accordance with GOST 18992-80 is used as a base adhesive for gluing cardboard boxes when packaging quick-frozen products on automatic lines. The specified adhesive does not meet the requirements for highly efficient gluing of cardboard boxes with a varnished surface without introducing an additional plasticizer, which is unacceptable for use in the food industry. The closest to the proposed invention is the composition of the adhesive, which includes a mixture of acid casein, low-viscosity hydrolyzed starch with a viscosity of 7% solution at 20 o C from 300 to 1500 mPas, alkali, sodium phosphate, urea and water in the ratio of parts by weight: 0.8-1 ,0:0.1-0.3:0.02-0.05: 0.3-0.5:0.1-0.2:3.0-5.0. The adhesive composition is used for labeling metallized and fatty vessels in automatic mode, but the adhesive properties of the adhesive are insufficient when gluing paper boxes at temperatures in the range of 10-20 o C (CZ 268047A, 07/31/90). The technical result is to preserve adhesion properties glue when gluing paper boxes with a varnished surface during packaging and storage of frozen food products. This technical result is achieved due to the fact that in water-soluble glue for the food industry, including a mixture of casein solution containing active additives and a starch-containing product, the casein solution with active additives has a mass concentration in the range of 28-31.4%, and is used as a starch-containing product alkaline solution of oxidized starch mass concentration in the range of 23-24.8%, while the ratio of mass parts of casein solution with active additives and alkaline solution of oxidized starch is 5:1. As active additives, for example, urea, sodium phosphate, ethylenediaminetetraacetic acid are used, and as a starch-containing product - an alkaline solution of oxidized potato starch with a viscosity of a 2% solution at 20 o C equal to 10-13 s (according to GOST 9070-75). The advantage of the glue according to the invention is that the mixture of casein solution with a solution of oxidized starch in the presence of active additives gives the glue greater initial and final adhesion to the varnished surface of paper boxes, cooled to minus 10-20 o C by the frozen product contained in them, and during sharp temperature fluctuations during storage of frozen foods. Initial Set glue seam when gluing boxes at 10 o C it is 30-40 s, the adhesive seam is quite elastic and can withstand low temperatures from minus 5 o C to minus 32 o C. The adhesive composition is characterized by increased frost resistance. Tests of the adhesive for frost resistance at minus 40 o C showed that the composition can withstand at least 4 cycles of freezing and thawing.
Claim
Water-soluble glue for the food industry, including a mixture of casein solution containing active additives and a starch-containing product, characterized in that the casein solution with active additives has a mass concentration in the range of 28 - 31.4%; an alkaline solution of oxidized starch by mass is used as a starch-containing product concentrations range from 23 to 24.8%, while the mass ratio of casein solution with active additives and alkaline solution of oxidized starch is 5: 1.
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The invention relates to the dairy industry, in particular to the isolation of biologically active milk proteins, including pancreatic ribonuclease A, angiogenin and lysozyme
The invention relates to a method for preparing a meat replacement product, in which protein material, a hydrocolloid that is precipitated by metal cations, and water are mixed at elevated temperature until a homogeneous mixture is formed
The invention relates to the food industry. Casein is subjected to enzymatic hydrolysis at a temperature of 50±1°C for 24 hours, the ratio of enzyme concentration to substrate-protein concentration is 1:25. pH-statting is carried out with periodic stirring of a 1M sodium hydroxide solution or 1M of hydrochloric acid at a pH optimal for the enzymatic system consisting of chymotrypsin, activity 40 units, carboxypeptidase, activity 1980 units. and leucine aminopeptidase, activity 24 units. After hydrolysis, the enzymes are inactivated with live steam for 3-5 minutes. Pasteurize at a temperature of 85±3°C for 2-3 minutes and dry by sublimation drying. The invention is to increase nutritional value product with a relatively fast manufacturing process. 3 tab., 2 pr.
The invention relates to compositions of water-soluble adhesive compositions for the food industry, in particular to adhesive compositions intended for gluing cardboard boxes with a varnished surface when packaging frozen foods
Based on the nature of the base, adhesives are divided into inorganic, organic and organoelement. The classification of adhesives is shown in Fig.
Rice. Classification of adhesives
Inorganic based adhesives can be divided into silicate, aluminophosphate, ceramic and metal.
Organic adhesives include compositions based on natural and synthetic polymers, oligomers and monomers, and artificial ones. Moreover, during curing, monomers and oligomers turn into polymers. In the production of adhesives based on natural polymers, substances of animal (collagen, albumin, casein) and plant (starch, dextrin) origin are used. Synthetic rubbers and resins are used to produce adhesives based on synthetic polymers.
The classification based on the thermal properties of adhesive bases is based on their thermoplastic or thermosetting nature, which in most cases determines the areas of application of adhesives and sealants.
Thermoset compounds are typically the basis of structural adhesives. Thermoplastics and rubber-based compounds are generally used for gluing non-metallic materials. Adhesives based on thermosetting resins are often classified as compounds (English compound - composite, mixed). Compounds (epoxy, polyester, polyurethane, silicone, acrylate) harden as a result of spontaneous cross-linking of the base when a hardener is introduced or under external influence, for example, moisture from the air.
According to the gluing conditions, adhesives are divided into contact (gluing occurs without pressure) and sticky (gluing occurs instantly under pressure).
Contact adhesives are, as a rule, all adhesives containing highly volatile solvents. The least toxic, highly volatile substances are usually used as solvents: light hydrocarbons, cyclohexane, methyl ethyl ketone, acetone, xylene, ethers, chlorinated hydrocarbons. After applying the glue
on one or both surfaces and a short drying period, bonding occurs.
According to the nature of gluing, adhesives and adhesive joints are divided into reversible and irreversible in relation to the adhesive seam to heat, exposure to water or organic solvents.
Some of the irreversible synthetic adhesives do not require heating to cure, and therefore they are divided into cold- and hot-curing adhesives.
Useful from a practical point of view is the classification of adhesive materials according to the water resistance of the adhesive joint into highly water-resistant (the adhesive joint can withstand boiling in water), water-resistant (the adhesive joint can withstand being in water room temperature) and non-waterproof (the adhesive seam is destroyed under the influence of water).
Based on consistency, adhesive materials are divided into solid (in the form of tiles, flakes, powders, films, etc.), solution, dispersion, encapsulation and melts.
Solution adhesives are a solution of any polymer in water (water-soluble) or an organic solvent. Water-based mortar adhesives are based on animal (bone glue), artificial (methyl, CMC glue), synthetic (polyvinyl alcohol, melamine glue) or inorganic (silicate glue) origin. Such adhesives are the most environmentally friendly. Organic solvent adhesives have a synthetic base (a solution of synthetic rubber in cyanoacrylate). Their setting time is an order of magnitude shorter than that of water-soluble adhesives, but evaporation of the solvent worsens their environmental properties.
Dispersion (PVA) adhesives are a dispersion of a polymer in water, into which water-soluble polymers with high adhesion - polyvinyl alcohol, cellulose derivatives - can be added to enhance bonding strength. Water makes it possible to successfully use such adhesives for gluing porous, hygroscopic surfaces. Their disadvantages include a long setting time and low microbiological resistance of the adhesive joint (can be increased by introducing fungicides).
Encapsulated adhesives are contained in capsules to prevent them from curing prematurely.
Hot melts are thermoplastic adhesives that become fluid at elevated temperatures and remain solid at room temperature. Hot-melt adhesives are solid polymer granules, usually in the form of balls or sticks. A polymer pencil is used to charge a special device - a thermal gun, which is connected to the mains. The molten polymer is applied to the surface to be glued using the dot method. If the glue is made in the form of balls, then they are placed between the surfaces to be glued, and one of them is heated until the balls melt.
Mortar and dispersion adhesives can be thick, medium, or liquid. Thick adhesives are available in tubes and have a longer drying time. Medium adhesives are produced in bottles equipped with an applicator - a brush attached to a stopper. Liquid adhesives are produced in polymer bottles with an applicator - a thin steel needle.
Depending on the degree of readiness, adhesives can be single-component or multi-component. In the first case, they are produced and sold in finished form. Multicomponent adhesives (usually two-component, for example epoxy) are prepared at the point of consumption from components.
According to their intended purpose, household adhesives are divided into household, special, office and universal (semi-universal).
In practice, classifications are used according to the area of application of adhesives (for example, shoe, furniture, construction, labels), according to specific characteristics (for example, according to the types of load experienced by adhesive joints during operation (Appendix 2), classifications according to OKP and HS (adhesives are included in 35th group).
In the production of textiles, it is not always possible to get by with just a thread and a needle. In some cases, it may be necessary to connect fairly small parts. To solve the problem, you need to use a special glue that can withstand the effects of washing, ironing and other external influences.
Careful selection of the chemical composition of the glue makes it possible to make the substance stable enough so that the adhesive joints of the fabric do not lose their strength during operation.
Although the well-known PVA or instant glue is often used when working with fabric, it is better to use a professional product from the chemical industry. This glue has a number of advantages:
- it does not spread;
- it is completely transparent, operates without traces, odor, and stains;
- good textile glue can survive many washes with aggressive agents.
These qualities are especially important in needlework: when creating decoupage, appliques or other kinds of crafts. In addition to being water resistant, the textile adhesive should also be heat resistant as it will often need to withstand hot ironing.
Textile glue, when applied, forms an elastic film on the fabric that can provide high-quality fastening even when the fabric stretches. This allows the glued parts to adhere firmly to the base.
Another positive property is the long hardening time, due to which it is possible to correct the necessary parts during the joining process to make the work more accurate.
Colorless glue is quite versatile - it can easily cope with gluing wool, cotton fabrics, synthetic and artificial products.
Types and scope of application
When working with textiles and other types of materials, several types of adhesives are popular:
- Contact glue is made on the basis of water and various types of solvents. It is used as furniture adhesive, when laying floor coverings, to ensure the connection of textiles with materials such as plastic, wood, glass, etc.
- Polyurethane synthetic based adhesive. Suitable for gluing PVC, plastic, wood, tiles, glass, etc.
- Neoprene adhesive composition. Used when working with textiles, leather, wood, rubber. It features increased heat resistance and strength.
- Nitrocellulose adhesive solution. It is most widely used in footwear factories, as it successfully bonds textiles to leather, etc.
- Rubber based adhesive. Quite elastic, used when working with leather, glass, textiles, rubber, wood. One of the varieties is latex glue.
Acrylic glue can also be used for textiles. It has gained a reputation for being versatile by providing good joints between different materials.
Additionally, classification can be made based on the method of applying glue to the fabric surface. This category distinguishes between aerosol adhesive, sold in a can, and sprayable textile adhesive in the form of a spray.
Make your own fabric glue
It is not always possible to purchase professional textile glue. Therefore, if you have the necessary components of the mixture at hand, and you need to glue something together as quickly as possible, you can do adhesive solution on one's own. Here are a couple of recipes:
Dextrin glue
To prepare the composition you will need water and starch. The latter should be placed in enamel dishes, then place in drying cabinet. It must be there at a temperature of 160ºC for at least 2 hours.
The next step is to boil water and add the resulting dextrin to it in a 1:1 ratio. Stir the mixture until the dry crumbly substance is completely dissolved in the water. Adhesive composition must be applied as soon as possible as it hardens quickly.
Casein glue mixture
As in the previous recipe, you only need 2 ingredients - casein and water in a 2:1 ratio. The liquid is added to the container with dry casein in a thin stream.
The mixture should be stirred constantly to achieve homogeneity. This mass also quickly hardens and becomes unusable.
How to remove glue from fabric
Sometimes it is necessary not to glue the fabric, but rather to clean it of the adhesive. For example, if during work the adhesive gets on your clothes. Depending on the type of adhesive solution that got on the textile, the method for removing the stain is selected.
Various substances can play the role of a cleaner:
- vodka
- acetone
- warm water
- cold water
- talc
- vinegar
- solvent
- special paint removers
- gasoline, etc.
Here are several working methods for removing glue:
- Glue moment quite easily soluble with readily available substances - it is removed from the fabric using a rag soaked in gasoline. If the stain is dry, you will need to use solvents or paint removers. But this is only when the fabric is sufficiently resistant to such substances.
- Rubber glue can be removed using a swab soaked in gasoline. The spot of the stain is also treated with gasoline, after which it must be blotted with a sponge and sprinkled with talcum powder.
- Wood glue can be removed by simply soaking the item for 5 hours in cold water and then washing.
- Removing Super Glue carried out using acetone. Before use, it is advisable to test its effect on a small piece of fabric. If textiles react poorly to the substance, it is better to use acidified water. For 1 glass of water add 1 tbsp. l. vinegar.
Textile glue is often called liquid thread because it can hold fabric parts together much more firmly than a regular needle and thread.
Handicraft stores, construction stores, or other specialized stores offer their customers a wide selection of products. Examples include types of textile glue such as Secunda, Alleskleber or Ekon.
Aqueous (water soluble.— Ed.) Paint binders are colloidal substances that are highly adhesive, so most of them are also known as adhesives. According to their composition, they are divided into carbohydrates of plant origin, which include gum arabic, starch, tragacanth and cherry glue, and protein substances of animal origin - casein, protein, albumin and skin, bone and fish glue. In addition, these include water-soluble cellulose derivatives, as well as water-soluble artificial resins.
Persistence. All of the listed substances are very stable, especially from the optical side, because they do not turn yellow or darken at all (except for egg white); With this very valuable property they are superior to both drying oils and resins. Their disadvantage is that they swell in a humid environment and then easily undergo decomposition caused by microorganisms, mold and rot. In this regard, the most stable are cellulose ethers, such as tylose, which do not decompose when exposed to water. They dry as a result of simple evaporation of water, that is, a definitely physical process, and after drying they no longer undergo either oxidation or polymerization. Therefore they are completely resistant in dry environments.
Light refraction. Dissolved aqueous binders, as a rule, contain from five to eight times the amount of water, which, upon evaporation, leaves cavities filled with air between the pigment grains. Since air has a very low refractive index, it is quite natural that gouache and tempera paints after drying turn out to be more opaque even when they contain
glaze pigments in oil technology. Their optical character appears only with a very strong binder when no significant evaporation of water occurs: gum arabic, cherry glue, dextrin, which have a high refractive index of light ( n==1.45) and giving darker and more saturated colors than other water-based binders. Blue paints retain their excellent tone even in a thicker coating layer only with low refractive index binders - glue, gelatin and protein.
Rice. 14. Paint changes when drying
A - wet water paint: pigment grains are surrounded by a liquid aqueous binder; B - the same paint after drying: binders are concentrated between the contacting surfaces of the pigment particles. The remaining space is filled with air. When dry, tempera paint is lighter in color; C - dried oil paint: pigment particles are completely surrounded by solid linoxin. Oil paint does not change during the drying process.
Solubility. Most of these substances dissolve directly in water and can be dissolved again when dry. Due to this property, they belong to reversible colloids. However, some of these binders only swell in water and dissolve in it only at elevated temperatures or after the addition of other substances, such as alkaline ones. Since after drying they are no longer soluble in water, they are classified as irreversible colloids.
Some soluble binders can be rendered insoluble by appropriate additives, such as glue by adding formalin, or by certain processes, such as albumin by heating to 80°C. Waxes and resins that repel water can either be emulsified or partially saponified by exposure to basic compounds, thereby obtaining aqueous paint binders that do not dissolve after drying. All irreversible binders are very well known in painting, since they allow work on a painting to continue immediately after the paints have dried, and the painter does not have to fear that the lower layer will dissolve or be damaged. In the attached table, aqueous binders are divided into two groups depending on whether they are water soluble after drying or not.
|
Aqueous binders |
Soluble (after drying.— Ed.) |
Insoluble (after drying.— Ed.) |
|
a) Plant origin |
Gum arabic |
|
|
Cherry glue |
Saponified resins |
|
|
Dextrin |
||
|
b) Animal origin |
Glue, gelatin, protein, albumin |
|
|
Wax emulsion |
||
|
Shellac, water soluble |
||
|
Glue with alum added |
||
|
Albumin with the addition of formalin or calcium hydroxide 49 |
||
| c) Artificial | Polyvinyl alcohol | Aqueous dispersions of polybutyl methacrylate, polymethyl methacrylate and polyvinyl acetate |
Elasticity. Aqueous binders contain a greater or lesser percentage of moisture, which to some extent determines their degree of elasticity. The water content of binders is not constant; it fluctuates depending on changes in atmospheric humidity. This can manifest itself in dry environments by such a significant reduction in elasticity that the whole picture is compromised. For these reasons, hygroscopic substances are added to aqueous binders, the elasticity of which is usually not high enough, which retain some moisture in them even in very dry weather and prevent cracking and peeling of the painting. These include honey, sugar, molasses, glycerin, glycol, glucose and vegetable juices.
Chemists and technologists generally speak very disapprovingly of these plasticizing substances. Nevertheless, the latter have proven themselves well in the tempera of the old masters and in modern watercolors. Obviously, everything depends on the correct ratio between plasticizer and binder. For example, adding a small amount of honey makes the glue more elastic, but a large percentage of honey makes it sticky, especially in a humid environment; if you add it to paints, it will ruin them in a relatively short time.
The elasticity of the binder can be tested by the following simple method: a thin layer of the binder or associated paint is applied to the cardboard and left to dry. When bending the cardboard, the dried binder should neither crack nor come off; if this happens, then the binder is not elastic enough. In the same way, dried coatings on glass should not come off after being cut with a sharp knife, and the edges of the cut should be free of burrs 1*. If binder films remain in humid air sticky, this means that they contain too many hygroscopic substances, and this deficiency can also damage the painting.
Gelatin and all types of skin glue are highly elastic; bone and fish glue are somewhat less elastic; Starch is the least elastic. Dextrin, casein and gum arabic are fragile.
Surfactants. In addition to plasticizers, water paints they also add substances that have the ability to reduce the surface tension of water, which makes it possible for easier wetting of the soil with paint, as well as stronger adhesion of the paint to the soil. Substances with this property include ox bile, borax, alum (when painting on gold) and surfactants, which are produced in large quantities by modern industry. These are soaps of various compositions (and resin), sulfonated oils (so-called Turkish red oils), sulfonic fatty alcohols and various saponates. For painting purposes, we currently use only ordinary (traditional) means, such as, for example, ox bile, which we know has no harmful effects. New substances should be tested and the necessary experience gained. A good primer for miniatures painted with watercolors is ivory coated with ox gall, on which the paints adhere firmly when dry and do not peel off. Another example is an aqueous fixative (2% solution of gelatin or casein in water), which, due to the high surface tension of water, is difficult to wet pastels and charcoal drawings. If we add approximately 30% ethyl alcohol to such a solution, which reduces the surface tension of water, then the fixative moistens pastel or coal dust more easily, and the fixing result is more favorable.
For preserving aqueous binders, we can primarily recommend camphor, which perfectly preserves and protects aqueous solutions from decomposition and molding. It is enough to add a few small pieces of camphor to the bottle with the solution to protect it for several weeks. Camphor floating on the surface disinfects the air space above the liquid; it dissolves very slightly in water (fractions of a percent) and completely evaporates when the paint dries. We can also add a small amount of a saturated solution of camphor in turpentine or ethyl alcohol to aqueous solutions. Since in practice, preservation with camphor has fully justified itself, it is unnecessary to use other often recommended means, such as acetic, carbolic and boric acids, since these acids can adversely affect both pigments and binders.
Glue. The main raw materials for the production of glue are bones, cartilage and skin, which contain a protein substance called collagen. As a result of heating to 80-90 ° C, collagen turns into gelatin, which is not pure, since it contains other proteins (keratin, elastin, mucin, chondrin) and, in addition, various inorganic salts and up to 15% water. The adhesives are extracted from bones and skin by boiling. The color and transparency of the glue are not indicative of its quality, which depends both on the purity and on the type of raw material from which it was obtained.
Skin glue is commercially available as gelatin or rabbit glue in varying degrees of purity. We distinguish it from bone glue by the fact that its aqueous solution does not become cloudy when alum is added.
Gelatin is sold in the form of thin, transparent and completely colorless slabs. The purest is gelatin for bacteriological purposes. Edible gelatin is also very pure. Its distinctive property is elasticity. Gelatin tiles can be bent and twisted and are unbreakable at normal air humidity. Due to this elasticity, gelatin is indispensable in the manufacture of chalk soils, the elasticity of which is the main condition for the strength of the picture. Technical gelatin, sold in thin yellowish slabs or as a granular powder, does not have the elasticity of edible gelatin.
Rabbit glue is imported from France. It is brownish-gray in color, opaque, and sold in the form of tiles (usually square rather than oblong) with strongly projecting edges. Goldsmiths and carpenters (who make frames) who have extensive experience working with chalk gold primers (very similar to painting primers) consider this type of glue to be the best.
Bone glue - regular variety wood glue, has a slightly lower adhesive ability and elasticity 51 than leather glue. Sold either as thick slabs or as brown grains. The tiles have very jagged edges; they are difficult to grind. Their fracture is conchoidal and glassy shiny. Bone glue is acidic and therefore its solution must be neutralized. The acidity level of the adhesive is determined by placing wet blue litmus paper on the adhesive tile. White glue is bone glue containing some white pigment such as chalk, lithopone, barite or zinc white.
Fish glue is obtained from fish bones and scales 52 . It is hygroscopic and easily dissolves in water. The best type of fish glue is Astrakhan. With the addition of 30% acetic acid it produces a well-known technical adhesive that remains liquid in the cold, called syndeticon.
Sturgeon glue 53 goes on sale in the form of transparent, fibrous and flat pieces that swell slightly in cold water and slowly dissolve in hot water. This type of fish glue belongs to the strongest adhesives in general.
Glue solubility. As a typical colloidal substance, glue does not dissolve in cold water, but swells strongly; it absorbs minimally as much water as it weighs. If we heat the swollen glue to 35-50 ° C, then it melts into a syrupy liquid, which cools again and turns to cold. And only as a result of strong dilution with water in a ratio of 1:50 (that is, 20 G glue dissolved in 1 l water) the glue remains in a liquid state and at normal temperatures. We do not dissolve the glue by directly boiling it in water, since boiling would cause it to lose its adhesive ability. Place the glue tiles in cold water for 12 hours and, after they swell, dissolve them in a water bath. The glue has the special property that at a temperature close to the boiling point of water, it becomes partially insoluble in water and settles on the walls of the vessel, where it burns. The most suitable solution for dissolving glue is a copper pot with a jacket, which is filled with water. The glue then does not lose its elasticity even with repeated heating 54 .
By its nature, the glue is a reversible colloid. Once dry, it can again be dissolved in water. Some substances, such as alum 55, formalin and tavnin, give it the properties of an irreversible colloid. We add alum to the adhesive solution in an amount from 1/5 to 1/3 of the weight of dry glue. Chromium alum is even more effective; however, it turns the glue yellow. Under the influence of formalin, the glue turns into a waterproof substance - formogelatin. It can only be destroyed by prolonged boiling in water or 15% hydrochloric acid. Glue painting or adhesive coating fix by spraying a 4% solution of formaldehyde in water or its mixture with ethyl alcohol. The same effect can be achieved by treating the coating with formaldehyde vapor. From experience with the gelatin coating of photographic plates cured with formaldehyde, the suspicion arises that the formaldehyde spoils the glue, which after a few decades turns into powder on the surface. The safest is considered to be the addition of alum, which, however, acts as a weak acid and adversely affects pigments that are sensitive to an acidic environment.
Purity. In factories, glue is bleached with bleach or sulfuric acid, and therefore it often contains residues of these substances. If the water in which the tile adhesive is placed for swelling turns brown or greenish, this means that the adhesive contains soluble salts. In such cases, the water must be changed several times until it becomes clear. The presence of acid in the adhesive solution is determined using blue litmus paper. If the paper turns red, the glue is neutralized with ammonia, which is added drop by drop until the litmus paper turns blue again.
Elasticity. The most valuable property of glue is its elasticity. The elasticity of the glue in relation to other adhesives used for the production of pictorial soil was determined experimentally as follows: gelatin, casein and gum arabic were applied to the glass in layers of equal thickness. When they were dry and removed from the glass as thin transparent films, the gelatin film could be bent and rolled without cracking; casein - it was impossible to bend at all, since with slight bending it cracked; in the same way, the gum arabic film turned out to be fragile. Since the strength of the painting depends on the elasticity of the soil, which must overcome the stress that occurs when the base is bent, casein is a completely unsuitable binder for soils. It is necessary to carefully select the highest quality grades of leather glue and not to use less elastic grades 56 .
The elasticity of adhesives has a significant impact relative humidity air. At normal atmospheric humidity and temperature, gelatin contains 14-18% water, which acts as a plasticizer. When the air is significantly dry, gelatin loses most of its water, as a result of which its elasticity decreases. If you heat a slab of gelatin for a certain time to 60-80°, it becomes so fragile that it can be easily broken. The same thing happens if you dry adhesive primers in direct sunlight or near an oven; they crack even though they were cooked just a few hours before. Microscopic cracks may form in the ground, invisible to the naked eye, which are the source of further destruction of the painting. Glue that has dried out in the sun or at high temperatures is a factor that can accelerate the destruction of a painting by several decades. To reduce this danger, hygroscopic substances are added to the glue to increase its elasticity. These are honey, glycerin, molasses and candy sugar (candy). Excessive addition of these agents should, however, be avoided as if large quantities are added the adhesive becomes sticky in wet weather.
Strength. In a dry environment the adhesive is very strong. Its adhesive ability, adhesion, strength and elasticity do not decrease over time. Wooden boards and the parts of the statues, glued together with glue, remain for centuries more durable than the wood itself. As a result of aging, the glue swells less in water and becomes insoluble. It is one of the most durable organic substances. With chalk or unfired gypsum it produces primers for painting that have been perfectly preserved for several thousand years, since the time of the most ancient Egyptian dynasties. However, the glue is fragile in a humid environment, in which it decomposes under the influence of microorganisms. Its strength in a humid environment can be increased by adding alum, carbolic or boric acid 57 .
The reasons why glue, which is superior in elasticity to other water-soluble binders, is used relatively little as a binder for paints, should be sought primarily in two of its properties that are unfavorable for painting: 1) it causes strong surface tension, 2) its solution gelatinizes under normal conditions. temperature.
1. In professional language, we talk about glue that it “pulls.” In enamel or porcelain vessels in which glue was stored and on the walls of which it dried, enamel or glaze, and often pieces of porcelain, quickly jump off. This phenomenon, indicating the high tension that the glue causes on the surface of the material on which it was applied, gives an idea of possible damage to the painting if too much glue was added to the paint or primer. If pigments are rubbed on an aqueous solution of glue whose concentration exceeds the ratio of 1:10, the paint peels off easily. Adhesive binders of lower concentrations from 1:15 to 1:20, although they do not have this disadvantage, however, after drying the paint becomes lighter, since as a result of the evaporation of such a large amount of water, air penetrates between the pigment particles. Although such an adhesive binder does not contribute to the destruction of paint layers, it is not enough for the paints to retain their saturation even after drying. Therefore, the use of glue as a binder for paints is limited only to gouache techniques 58 and decorative painting.
2. The gelatinous state of the adhesive solution at normal temperatures is also a significant obstacle when painting with adhesive paints. Clay mugs with paints have to be heated, and in colder weather the paint freezes directly on the brush so much that it becomes impossible to paint. Only very weak solutions remain liquid in the cold. Therefore, painters have long sought to produce a more concentrated adhesive solution that would remain liquid even at normal temperatures. The adhesive solution acquires such properties both as a result of prolonged boiling and putrefactive processes, during which its colloidal gelatinous structure is destroyed. In past times, indeed, they wrote with such glue. Currently, glue is produced that does not gelatinize in the cold: either a large amount of acids (acetic, oxalic or hydrochloric) is added to the glue, or the glue is boiled with alkaline substances, that is, with caustic soda, lime 2*, and finally, various salts are added - thiocyanates , salicylates, nitrates and chlorides 59. The liquid glue produced in this way serves as a pillbox as a technical glue. For painting, it is possible to obtain glue with such properties and without harmful effects on it - only by adding chloral. Chloral hydrate has the form of transparent, colorless crystals that spontaneously evaporate in air without leaving a residue. Added in an amount corresponding to half the weight of dry glue contained in the adhesive solution. After twenty-four hours of exposure, the adhesive jelly turns into a liquid, which is suitable for use as a binder for paints or as a component of distemper.
Alkaline glue that does not gel in the cold is prepared as follows:
100 parts of glue are left to swell and then dissolved
by heating. Then they add:
20 parts slaked lime or caustic soda
20 parts water.
All this is heated in a water bath until the glue stops getting cold after cooling. However, such glue is much more fragile than regular glue.
Glue is also used to make artificial materials, casting compounds, adhesive solutions and fixatives for pastels. When gluing plywood, hexamethylenetetramine is added to the glue, which releases formaldehyde when heated, which hardens the glue.
Adhesive solutions:
100 parts gelatin,
35 parts water
100 parts glycerin,
60 parts sugar
1.5 parts boric acid.
Glue has been used as a binder for paints and chalk or gypsum primers since the early Egyptian dynasties. In the dry climate of Egypt it turned out to be absolutely durable. Pliny names glue in the list of binders of Egyptian painting along with vegetable glues, milk, eggs and wax. In medieval painting, glue was of great importance in the countries located north of the Alps. It was also the main binder of colors in oriental painting - Indian and Chinese.
The glue from which chalk and gypsum primers for paintings on boards were made in the Middle Ages was leather. Heraclius (12th century) writes in chapter 26 3* about glue: “Take parchment or its trimmings, put it in a pan of water and boil it.” According to Theophilus (XII century), chapter 18 4*, glue was made from horse, donkey skins and the skins of large cattle, cut into small pieces.
Cennino Cennini also made glue from leather for gypsum primers. He writes about this in chapter 110: “It is a glue that is made from goat or ram parchment and from the scraps of such skins. The trimmings are thoroughly washed and soaked the day before. IN clean water cook for a long time until the glue mass boils by 1/3. And if you don’t have tile adhesive, use this glue and not another to prepare gypsum primer for boards. There cannot be a better glue” 5*. According to Herminea, Mount Athos manuscript, chapter 4, the glue was made from a skin that was soaked in lime water for a week, thereby removing hair and dirt. Then it was boiled until it was mushy; After cooling, the resulting glue was divided into tiles and dried.
When in a later technical literature Renaissance and Baroque eras mention glue for soils, they always mean parchment glue obtained from the skins of lambs and goats. (Vasari, Filarete, Palomino, de Mayerne and other authors of recipes all cite this type of goat glue.) Blue pigments were bound with glue back in the days when oil painting was already completely dominant. In the 18th century, gouache paint, loosely bound with glue, replaced the old tempera, which was almost completely forgotten. In his dictionary of painting (DictionnaireportatifdePeinture), A. J. Pernety described several different varieties glue.
1. Glove glue from scraps of leather from which gloves were made. These scraps were soaked for several hours in hot water, and then cooked on low flame. This type of glue was also made from waste parchment.
2. English glue (colle-forte), made from large fish, cartilage, hooves and cattle hides.
3. Flemish glue, which differed from English glue only in that it was cleaner and better made. Served for painting with watercolors.
4. Colleabouche (corresponding to the glue used in Italy under the name "colladolce", and in Germany "muudleim"), made from Flemish glue, to one pound of which was added a little water and 8 lots of candy sugar.
5. Orleans glue was obtained from pure colorless fish glue, which was soaked for 24 hours in weak lime milk and then boiled in water.
6. Gilding glue (colleadorear) was a mixture of eel skin glue and egg white.
From this review it is clear that, along with leather glue, other types of glues began to be used in the 18th century, especially bone and fish glues, which Van Dyck considered unsuitable for soils back in the 17th century 60 .
The first industrial production of glue was organized in Holland at the end of the 17th century. With modern industrial production After using glue, the skins are first treated in lime water, then they are dried, cut and boiled in closed boilers, where steam is supplied under pressure. The boiled glue falls onto the cooler bottom and does not burn. Then the adhesive solution is concentrated in a vacuum, cleaned and poured onto water-cooled tables. After hardening, it is divided into slabs and dried on sieves.
Casein is a phosphoroprotein contained in milk in the form of calcium salt 61 . It is obtained (from skim milk.— Ed.) precipitation of casein with lactic or hydrochloric acid in the form of cottage cheese, which is washed with water, dried and ground into a light yellow granular powder of an acidic nature. Casein powder does not dissolve in water, it only swells slightly in it. Swollen casein can be easily dissolved by moderate heating by adding alkalis - soda, caustic potassium or sodium, borax, ammonia or lime. To obtain neutral salt soluble in water, you must add 100 G casein 2.8 G caustic sodium. For painting purposes, casein is dissolved with ammonia, or with ammonia salts, the excess of which completely evaporates, or with lime (for wall painting).
Ammonia casein is obtained as follows: 40 G casein is left to swell at 1/4 l cold water for 2 hours, then heated to 50-60 ° C, slowly add 10 Gammonia and stir for several minutes. From the milky-turbid casein solution, contaminants and undissolved components quickly separate out and settle to the bottom, which are separated by decantation. Old casein, which has been stored for more than a year, does not completely dissolve; some grains only swell; they should be removed by straining or filtering. Casein intended for the production of halalite is sometimes commercially available. This variety is obtained from milk by precipitation with enzymes rather than acids. It dissolves only slightly with alkalis, and therefore cannot be used in painting. When purchasing a large amount of casein, it is recommended to test it for solubility: 150 G casein soak for 2 hours at 60 cm 3 cold water; to the swollen casein add 2.3 g of borax dissolved in 15 cm 3 water, and stir for 10 minutes in a water bath at 50°C. Casein should be completely dissolved and there should be no swollen grains 6*.
Casein has great adhesive ability; Usually 5-10% solutions are strong enough. It remains liquid at 15-20% concentration; more concentrated solutions become gelatinous, like glue. Since casein quickly undergoes putrefactive destruction, it should be prepared just before use. However, if we add camphor to it, it will last for several weeks.
Casein is a typical irreversible colloid, because after drying it does not dissolve in water. It reaches maximum insolubility after 7-14 days. After drying, it gives a transparent, shiny coating, characterized by extraordinary fragility, much greater than that of animal glue. This property should be kept in mind when determining its suitability as a binder for primers or paints with which we want to write on movable substrates, in particular on canvas. Glycerin, of which the so-called Viber casein soil contains a significant amount, will not particularly help in this case, since glycerin evaporates over time.
Casein has an affinity for lime. It forms insoluble salts with it, due to which it is directly intended for wall painting. Its inherent lack of elasticity does not pose a danger in a fixed wall environment. It is best to prepare casein directly from fresh cottage cheese, which is first ground finely and then mixed with either 1/2 - 1/3 parts of powdered calcium oxide hydrate or with 1-2 parts of slaked lime. This thick, well-ground glue is diluted with water and left to settle so that the pure dissolved casein is separated from the excess lime that settles to the bottom. Lime casein dries and hardens unusually quickly; It absorbs carbon dioxide from the air, which converts calcium hydroxide into insoluble carbonate. If casein contains an excess of lime, it is not decomposed by bacteria and molds as easily as casein with a small amount of lime or as casein obtained with ammonia, borax, or soda.
Lime casein is added to paints when painting on fresh plaster and to insoluble paint coatings that must resist the effects of atmospheric agents.
Casein emulsifies with waxes, balms and oils into insoluble temoers. A solution of casein with borax or ammonium carbonate is prepared as follows:
A. 100 parts casein,
250 parts water;
B. 18 parts of borax (or 12-20 parts of ammonium carbonate), dissolved in
30 parts water.
Dissolved casein is diluted with another 250 parts of water before use.
Very weak 1-2% solutions of casein with 1/3 ethyl alcohol serve as fixatives for pastels and charcoal drawings.
Casein was already known in ancient times as a very strong wood ley. In the Middle Ages, Theophilus and Cennino Cennini mentioned him in this sense. Casein, however, was not used for the production of soils, and experiments in this direction began to be carried out only in the 20th century. Casein began to be used as a paint binder in the Baroque era, and only for wall painting. During this era, the Renaissance fresco technique had just been replaced by casein painting (on both dry and fresh plaster). Currently, a large amount of casein is spent on the production of artificial horny mass (galalit.— Ed.), which is casein treated with formaldehyde, or for gluing plywood. Insoluble putties are also made from casein using resin soaps or water glass.
Starch is obtained from potatoes, rye, corn and rice. It is obtained by washing in the form of a white, shiny, silk-like powder. It does not dissolve in cold water; in hot water it swells strongly and forms a so-called starch paste. The properties of starch depend on the type of plant from which it was obtained. Potato starch gelatinizes at 72°C, wheat starch at 62°C, and rye starch at 68°C. Individual varieties of starch can be distinguished using a microscope by the structure of the grains.
Starch paste is not stable; after 2-3 days, starch grains are released and it loses its stickiness. By repeated heating, you can again obtain a paste, but since it decomposes very easily, it must always be prepared just before use. The rapid decomposition of starch paste can be prevented by adding a small amount of formaldehyde 62 . Starch glues paper and other substances, but not wood. It is a much weaker adhesive than animal glue and does not cause such strong tension. Its adhesive ability can be enhanced by adding aqueous solution animal glue. In painting it serves as a binder for paints, and during restoration it is used to glue new canvas onto the canvas of old paintings 63 . For this purpose, starch paste is emulsified with balms. From the point of view of painting technology, its significance lies mainly in the fact that when it dries, it does not dissolve in water and only as a result of cooking does it go back into solution. Therefore, colorful glue with a starch binder can be applied a second time without fear of dissolution of the underlying layer.
The most common type of starch is potato starch. Starch paste is prepared from it in a simple way: stir 15 G starch in a small amount of cold water and then add 1/3 l boiling water The paste with less than fifteen times the amount of water is so thick that it cannot be applied with a brush. Starch paste mixed with powdered pigments produces gouache paints that dry like pastels, so they can be used for underpainting pastels. Starch binds paints weakly; when twenty parts of the water evaporate, only a small amount of solid adhesives remains, and therefore starch-bound paints can be used only in a narrowly limited volume, although they are optically completely stable, durable and insoluble in water. Like cherry glue, the starch binder gives the paint a pasty character, the paint does not flow and is more suitable for covering large surfaces than for miniature painting, for which it lacks fluidity and flow from the brush. Starch paste made from fine rye flour is more suitable for painting and preservation purposes than potato starch, since it produces less viscous solutions. It binds well to balms in tempera and can be added to other water-soluble substances, such as casein, with which it forms a good glue.
The starch paste turns into a liquid solution when heated to 120°C, and the starch grains isolated from it with ethyl alcohol then directly dissolve in cold water. The action of alkalis, oxidizing agents (hydrogen peroxide, permanganate), then acids, enzymes or ultraviolet rays also destroys the structure of the starch gel: although starch powder is similar to ordinary starch, it does not gelatinize, but dissolves directly in cold water; in this case, it loses its irreversibility in proportion to this solubility. Soluble starch, sold under various names, usually contains silken substances and must be neutralized with hydrochloric acid before use.
Starch coatings lose their elasticity over time and become brittle (either due to a decrease in the hygroscopicity of starch as a result of aging, or as a result of the activity of microorganisms), therefore it is useful to add small amounts of plasticizers to them - sugar 64, glycerin.
1. Starch paste made from rye flour:
100 parts finely ground rye flour,
100 parts cold water; after mixing add
500 parts boiling water and 5 parts formaldehyde.
Then dilute with water as needed.
2. Starch paste made from potato starch:
150 G potato starch,
100 G cold water; after mixing add 1/4 l boiling water.
3. Basic starch (liquid):
100 parts potato starch,
200 parts cold water,
10 parts of caustic potassium dissolved in
400 parts water.
The solution is neutralized and the medium is checked using litmus paper.
4. Starch emulsion with Venetian turpentine:
Add 40 parts of Venetian turpentine to the finished starch paste No. 1 and No. 3.
5. Starch glue:
100 parts starch paste made from rye flour,
90 parts yellow dextrin,
10 parts molasses,
30 parts Venetian turpentine.
The preparation of starch paste from starch grains has been known since ancient times. In China, documents glued with starch dating back to the beginning of the 4th century AD have been preserved. Cennino Cennini describes in chapter 105 the preparation of a starch paste made from sifted flour and water. In Vasari's time, canvas for painting was covered with primer, which also contained starch or flour. This type of soil did not disappear later, because kaolin soils bound with starch were described in manuals of the 19th century, for example by Bouvier.
When ordinary starch [containing 10-20% water] is rapidly heated, dextrin 65 is obtained. Dextrin can also be obtained by the action of acids on starch.
Yellow dextrin completely dissolves in hot water, and its 25% solution remains liquid even in the cold. When borax is added to the solution, it turns slightly brown and becomes even more liquid. Its properties (mainly in that when it dries it gives a shiny film 66 and again dissolves very easily in water) it is somewhat reminiscent of gum arabic. However, it is more fragile, and its adhesive ability and adhesion are much less. In any case, hygroscopic plasticizers should be added to dextrin: glycerin, sugar or honey. Dextrin has a high refractive index, and therefore, when mixed with pigments, it produces rich, deep tones. Together with glycerin, dextrin is used to produce cheap watercolor and water-soluble paints in tubes.
Dextrin solution:
100 parts yellow dextrin,
200 parts hot water,
30 parts glycerin,
camphor seed.
Dextrin glue for paper:
10 parts of borax are dissolved in 200 parts of water and 200 parts of yellow dextrin are added. Heat to a boil and add such an amount of hydrogen peroxide that the liquid becomes light. Preserve with two parts of carbolic acid.
White dextrin is less soluble than yellow dextrin. WITH hot water it forms a white paste, which upon cooling becomes so hard that it is not suitable as a paint binder. Office glue is made from it and gum arabic is adulterated with it.
Egg white contains 85-88% water, 12-14% a mixture of different proteins, mainly egg albumin, a small amount of mineral salts and fatty substances. In a thin layer, egg white, after drying, gives a transparent, shiny, but brittle film, while in a thicker layer, after drying, it cracks and hairline cracks form in it. Fresh, somewhat thickened and gelatinous whites become liquid when you beat them and let them sit. When heated to 65 ° C, it curls. It forms insoluble salts with lime, and when treated with tannin, it no longer dissolves in water when it dries. Unlike other aqueous binders, egg whites either turn yellow or turn orange-brown as they age.
Dry protein is a transparent, gum arabic-like substance that first swells and then dissolves in lukewarm water. By heating to 75°C it turns into a substance insoluble in water.
In painting techniques, protein is added to tempera or used as a binder for paints intended for miniatures. Since it is fragile, candy sugar is added to it, which increases its elasticity and eliminates its tendency to crack. Some painters use mixtures of proteins and sugar for temporary varnishing of insufficiently dry oil paintings, from which they wash off this varnish after about a year, replacing it with permanent resin varnish. Since protein is stabilized by light and is not easily washed off, it is more correct to abandon temporary varnishing 67 . In the polyment gilding technique, protein and polyment provide a high-quality primer for gold foil, which can be given a high shine by grinding and polishing with agate.
Egg white was the main binder of paints in medieval miniature painting. Already in old treatises of the 11th-14th centuries, where manuscripts with miniatures are reported, we find instructions on how to make the protein liquid so that the paint flows off the brush or pen more easily. Then the protein was beaten or pressed through a cloth or sponge and sugar, honey, and in some cases a small amount of yolk were added to it. However, protein was not used as a binder for all pigments without exception. Blue pigments, for example, were ground with gum arabic, which gave them greater transparency and depth.
Albumin is dried animal blood serum 68 . Unlike glue, it dissolves in cold water, but when the solution is heated to 80°C, it precipitates. With the addition of ammonium salts or lime it becomes insoluble in water, and since it is cheap, it is mainly used for insoluble decorative wall painting and for coating.
Albumin solution is prepared as follows: Water 90 parts,
albumin 50 parts,
ammonia (specific weight 0.9) 2 parts,
slaked lime 1 part.
The specified ratio must be strictly observed 7*.
Gums are air-hardened colloidal substances that flow from the cut bark of trees. For painters, gums that dissolve in water are important - gum arabic and gum fruit trees.
Gum arabic comes from the African acacia tree. It consists of potassium and calcium salts of arabic acid (C 5 H 3 O 4) n. Sold in the form of colorless or yellowish lumps with a highly shiny, conchoidal fracture. The most valuable variety is considered to be Hashab, originating from the Kordofan province. The Senegalese variety of African gum differs from the Kordofan variety in having a rougher surface, less shine, and also in the fact that it is slightly hygroscopic and produces thicker solutions. The Indian gum, called ghatti, and the Australian, called wattle, are less valuable varieties. Crushed gum arabic is also available for sale, but it is adulterated with dextrin, which is more fragile and has poorer adhesive properties.
In cold water, gum arabic dissolves slowly and gives a thick, highly sticky solution in a ratio of 1:2. A thin layer of dissolved gum arabic dries into a colorless, shiny, glass-like, hard film that can be easily redissolved in water.
In a dry environment, the film is very stable, does not turn yellow, or becomes cloudier? and does not weather, but it is very fragile, and therefore it is necessary to add hygroscopic substances such as glycerin, glucose or sugar to it. Gum arabic reacts slightly acidic, and its solutions quickly turn sour and moldy. To prevent this, a grain of camphor, borax or a microscopic amount of formaldehyde is added to the solutions. Solutions of gum bica have low viscosity, they are liquid and at a significant concentration, and with this property they are superior to all water-soluble binders. Therefore, miniatures are very suitable for the technique, because they allow precise execution of even the smallest details. Refractive index of gum arabic ( P= 1.45) and the paints rubbed on it are distinguished by their saturation and depth. Gum arabic easily forms emulsions with oils, balms and distemper varnishes, which are shiny after drying. Gum arabic solution:
100 parts of Kordofan gum arabic
150 parts water
leave to swell for a day, after which it is dissolved by heating, then a piece of camphor is added for preservation.
Solution for the formation of an elastic film of gum arabic:
100 parts Kordofan gum arabic,
200 parts water,
10-50 parts glycerin,
These solutions can be neutralized with lime or borax (three parts borax to 100 parts gum arabic). However, some varieties of gum arabic become very thick with alkalis and only after adding sugar they become liquid again.
Already in the Middle Ages, gum arabic, along with egg white, served as a binder for paints for miniatures. We find mention of this in the oldest medieval recipe books. A 12th-century Neapolitan codex gives a mixture of gum arabic with egg white and honey as a colorless primer for gold foils. Boltz von Rufach, in his Illuminierbuch, published in 1526, names gum arabic among the main binding paints for miniatures.
Cherry gum (cherry glue.— Red.).Gums flow from the wounded bark of fruit trees, which, depending on their origin, are called cherry, plum, etc. glue. In appearance, these gums are similar to gum arabic; they differ from it only in that they do not dissolve in water, but only swell. They absorb from twenty to thirty times the amount of water and only if the swollen gum is heated and pressed through a sieve can it be made into mucus, which can be used for painting. Since the solubility of fruit tree gums decreases greatly with longer storage, it is better to dissolve freshly harvested gum, because it gives a more liquid and, moreover, more concentrated solution. Paint containing cherry gum, even with a very weak binder, is pasty, plastic and does not spread. Currently, cherry gum is used only as an additive to special temperas. Under the influence of hydrochloric acid, cherry gum dissolves directly in water; however, this solution must then be neutralized. Cherry gum is a soluble colloid; hence, once dry, it is soluble in water.
According to Theophilus' tract DiversarumartiumSchedula, it can be judged that in Northern Europe in the 12th century they wrote only with this gum. According to the description, the paints were applied three times successively, and then varnished with a thick oil varnish, which was dried in the sun. Since Theophilus writes in his treatise that the gum should be cut (but in no case crushed), it can be assumed that then the gum was not as hard as the varieties currently sold. Freshly harvested gum was soft, plastic and gave concentrated solutions, like gum arabic.
Tragant is the dried sap that oozes from the cracked or cut bark of certain shrubby species of Astragalus native to Greece and central Asia. In water it swells greatly and turns into jelly, which should be heated and pressed through the canvas so that it becomes at least a little liquid. In exceptional cases, tragacanth is added to tempera, and pastels are bound with its 2% solution.
Water-soluble cellulose ethers. Various varieties Methyl-, dimethyl-8* and hydroxymethylcelluloses are marketed as water-based paint binders and as adhesives. Dissolved in ten times the amount of water, they form more or less viscous solutions that serve as distemper bases or direct binders for the preparation of paints, suitable, for example, for decorative painting on walls. They are completely neutral and do not degrade as easily as vegetable and animal glues. They are alkali-resistant, easily form emulsions with tempera oil, and grated paints are easy to work with. A wide variety of derivatives with different properties are available for sale under the name tylose, glutolin or glutofix. For painting, only those varieties that are specifically intended for this purpose should be used.
Synthetic water-soluble binders. Some artificial resins also have the ability to dissolve in water; such solutions are used both as adhesives and as binders for paints and primers. Similar water-soluble artificial resins include:
polyvinyl alcohol (polyviol),
polyvinylacetal (movital),
polyvinyl methyl ether (igevin),
phenolic (phenolic-formaldehyde.—Ed.), water-soluble resins (resinol).
In the field of artistic painting, these new materials have not been sufficiently tested, but they have proven themselves in the production of technical emulsion varnishes. Polyvinyl alcohol has shown good properties for preserving fabrics and for fixing falling paint layers on wall paintings.
1* E. Stock. TaschenbuchfurdieFarben- und Lackindustrie (Handbook of the paint industry), 1943.
2* D.I. Kiplik (“Painting Techniques,” p. 117) advises adding 4% slaked lime to a 20% adhesive solution.
3* Negaslius. De coloribus et artibus Romanorum. 1873,
4*Theopbilus. Schedula diversarum artium. 1874
5* TranslationF. Topinki.
6* E. Stock, part I.
7* N. Neaton. Outlines of Paint Technology. London, 1947.
8* Apparently carboxymethylcellulose and methoxycellulose are assumed (ed.).
