What metal is called tin can metal. Tin life

For the manufacture of cans, white and varnished tin is used.

Tin cans

Tin cans are made of tinplate (thin sheet iron coated on both sides with an even thinner layer of tin). The surface of iron sheets is coated with tin to prevent oxidation of iron by atmospheric oxygen. The iron sheet has a thickness of 0.24-0.35 mm. Thinner tin is used for the manufacture of small cans, thicker - for large ones with a capacity of 3 liters or more. However, at present, the canning industry has begun to manufacture cans from thinner tin, 0.20 mm thick. Cans made of thin tin are convenient, they are much easier to open. In addition, iron consumption is reduced by almost 25%.

Tin for tinning (coating) of iron is used the purest, without any impurities of other metals, especially harmful to humans. The layer of tin covering the surface of the iron sheet is needed not only to keep the iron from rusting, but also to protect the canned food from direct contact with the iron. In the case of such contact, a rapid darkening of canned products occurs; destruction of vitamin C in them, the appearance of a metallic taste, as well as the formation of black spots of iron sulfide on the inner surface of the cans, due to the reaction between iron and sulfur compounds formed during the heat treatment of some protein products.

Tinning of tin with tin is carried out at metallurgical plants. This process is often carried out by the so-called hot method - by immersing clean pickled sheets of iron in baths of molten tin. At the same time, a thin layer of tin remains on the sheet of tin. If you cut a plate of tinplate 10 × 10 cm in size, then the weight of tin on both sides of the plate will be only 0.4-0.45 g.

But the industry has already introduced a new, progressive method of tinning tin - electrolytic. The new method makes it possible to drastically reduce the consumption of tin. In addition, the speed of tinning increases several times.

Tinplate is a good, convenient material for cans. In them, the preserved product retains its quality well.

Tin cans made of lacquered tin

Most canned food at our enterprises is produced in tin cans. However, there are many canned foods, for which the quality of a tin coating is not enough to preserve the quality (pickled vegetables and fruits containing acetic acid, or various canned foods with tomato sauce, fruit compotes from sour fruits). Under the action of acids that are part of these canned food, tin can dissolve, in some places on the inner surface of the cans there may appear areas of iron that are not coated with tin. To prevent this from happening, such canned food is made in lacquered tin cans. Tinplate is coated with a special food varnish, which completely eliminates the possibility of dissolution of metals by the product. In canning food varnishes, the presence of any substances harmful to humans is not allowed. Lacquered cans are suitable for making all kinds of canned food.

Readers may wonder - if so, why aren't all tin cans made from lacquered tin? From what has been said above, it is clear that this is simply not necessary. In addition, varnishing, of course, increases the cost of cans and should be done only in case of real need.

We should dwell on the frequently occurring cases of darkening of the inner surface of unlacquered tin cans with the formation of spots or stripes of various shapes of a bluish-brown color. This phenomenon is observed in canned foods that contain a lot of protein (stew, green peas, canned fish, etc.). When such products are heated, sulfur compounds are formed during the time, which immediately react with the tin covering the inside of the jar. The resulting substances form the thinnest bluish film. It is harmless, insoluble in water and firmly adheres to tin. Its only drawback is that it somewhat worsens the appearance of the inner surface of the can (the phenomenon of "marbling").

In lacquered tins, marbling is almost not observed. Therefore, in recent times, canned meat is often produced in lacquered jars.

The sizes of cans are standardized. The standards set the exact (up to tenths of a mm) dimensions of each type of can. There are more than 30 types of tin cans. For each species, the exact dimensions are determined, a specific number is assigned, and a list of canned food is recommended for which these cans are intended. The most common are cylindrical cans of various capacities.

Canned fish is often prepared in rectangular, oval and elliptical jars. These banks have a small height and a shape that is convenient for laying oblong fish in them without damaging them.

The most widely used tin packaging, it is light and has a high thermal conductivity. Tin containers of the required dimensions can be made at canning factories. However, tin packaging has a number of disadvantages.

When canned food is stored in tinplate containers, corrosion processes occur, i.e., the transition of the metal under the influence of the environment (air or food products) into various oxide compounds or salts of organic acids.

The outer surface of a can when stored in warehouses, especially unheated ones, begins to become covered with oxidation products (rust). This process takes place despite the tin layer covering the iron base of the tin, because the tin layer has pores. Usually, when hot-tin coated, tin has 6-10 or more pores per square centimeter. Each point is a microelement where corrosion processes take place under the influence of moisture. In autumn, spring, and for the south and in winter, during the day in warehouses, the air temperature changes dramatically and, with its high relative humidity, conditions are created when air saturated with water vapor cools when it comes into contact with stacks of canned food (the temperature of canned food does not change as sharply as air ), near the surface of the tin container, it becomes supersaturated with water vapor and drops of moisture are deposited on the tin surface. In drops of moisture that have settled on the contaminated surface of the tin, an electric element iron-tin is formed, and the conductor is water contaminated with organic and inorganic compounds. Iron and tin have different electrical potentials. Under these conditions, iron dissolves, while tin is preserved. The water dries up, and the tin becomes covered with rusty spots.

In contact with canned food products containing organic acids, the electrical potential of tin changes depending on the pH of the canning medium, and the transition of tin to canned food begins. For this reason, health authorities have rationed the tin content of canned foods. The maximum content of tin in vegetables and other types of canned food should not exceed 200 mg per 1 kg. Coating with varnish or enamel on the inner surface of the cans significantly reduces the transfer of tin into canned food.

In addition to hot-tinned tinplate, canneries use white rolled tinplate without varnish and varnished grades ZhKL (hot-tinned lacquered can) and EZhKL (electrolytic tinned can lacquered) for the manufacture of cans and lids for glass containers. Rolled lacquered tinplate should have a shiny surface without lacquer drips, bubbles, unlacquered spots. The surface color of the tin should be uniform. The tinplate is available in various widths to reduce waste when making cans.

To reduce the consumption of tin, electrolytic (non-hot) tinned rolled tin is produced. The consumption of tin during electrolytic tinning is reduced by 2-3 times. Electrolytic tin plate is coated with a double layer of varnish.

In addition to tinplate, rolled tinplate of the ZhChKL brand (black lacquered canning tinplate) is produced, from which lids for glass containers are produced.

A number of works were carried out on the use of aluminum for the manufacture of canning containers and lids. Aluminum molds well. Any violations of the aluminum surface during stamping are not as important as in tin, because the oxide film in places of violation under the influence of oxygen, air is quickly restored. Aluminum surface lacquering provides additional protection against corrosion. Aluminum corrosion products are white and are not regulated by health authorities. But when using aluminum, there are also a number of difficulties: aluminum cannot be soldered, therefore it is impossible to make prefabricated cans from it, it has a lower mechanical strength compared to tin, therefore, the rejection of cans increases during their manufacture and during loading and unloading operations. Aluminum has a reduced corrosion resistance to the acidic environment of canned food, therefore, despite the varnishing of the inner surface of the cans, it is only suitable for packaging canned food with a pH of about 7 (meat, fish in oil, natural vegetables).

To combat corrosion, tinplate or other materials from which cans are made must be varnished. Varnishes and enamels used to cover tin should not contain harmful impurities: salts of heavy metals, substances that give the product an extraneous taste, smell or color.

Lacquer and enamel films must withstand mechanical and thermal processing, which is necessary for the manufacture of cans and technological processes. The film should not flake off the surface of the tin, form cracks, but it should withstand heat without change during sterilization for 2 hours. at a temperature of 100 ° or 1.5 hours at a temperature of 121 °.

The density and strength of the lacquer film is checked by boiling samples of varnished sheet metal for 2 hours. in 50% sugar solution, 3% common salt, 12% tomato puree and 3% acetic acid. Lacquer coatings must not be altered by this treatment.

The tin from which containers for canned food containing a lot of protein substances (crab, chicken) are made is coated with protein-resistant enamels.

Enamel must withstand two hours of boiling in a 3% sodium chloride solution or in a solution of 3% gelatin and 1% sodium chloride. The solution is saturated with hydrogen sulfide (H 2 S).

The composition of varnishes includes natural or synthetic organic resins (copal, etc.), oils (tung, linseed) and solvents (turpentine, spirit).

Protein-resistant enamel is made from varnish with the addition of zinc oxide (ZnO). This is necessary because during the sterilization process, protein compounds begin to break down under the influence of temperature, and in the process of decomposition, sulfur compounds are released, which, reacting with tin tin, give deposits on the surface of the tin (black-blue color) tin sulphide (SnS). If these protein breakdown products come into contact with an enamel film that contains zinc oxide, then white zinc sulfide (ZnS) compounds will form on the surface of the film, and not black-brown deposits (SnS).

Rotary machines are used to apply varnishes and enamels on tin. A special mass is applied to the shafts of the machine, which includes gelatin. After coating, the tin sheet enters the furnace. The varnish is annealed at a temperature of 180-220°. During annealing, the solvent evaporates from the varnish and the oil polymerizes. The film is made hard, elastic and insoluble in canning products.

To obtain good coatings (non-porous), the varnish is applied in two layers. The thickness of the coatings is 10-15 microns. The outer side of the can is sometimes lithographed. They apply drawings, printing, paints on special machines. In recent years, canneries have been equipped with machines capable of lithographic printing in four colors. A jar, the inner surface of which is varnished, and the outer surface with lithography and varnish, is much less exposed to corrosion.

According to the manufacturing method, tin cans are divided into prefabricated and seamless. The main type is a prefabricated cylindrical tin can (Fig. 3); it consists of three parts: body, bottom and cover. The body of the can is made from a blank (blank) having a longitudinal seam. The bottom and lid are connected to the body with a double seam. The longitudinal seam is made into a lock inside the can and soldered outside.

On the left - the ends of cans: 1 - with a bent flange; 2 - with a rounded flange; on the right - a double seaming seam: 1 - before the rollers work; 2 - after the first operation; 3 - after the second operation.

The end parts of the longitudinal seam are overlapped. If the longitudinal seam along the entire height is made into a lock, then when it is connected to the lid and bottom, so many layers of tin will be obtained (eleven instead of seven) that the tightness of the seam cannot be achieved.

The bottoms and lids have reliefs that create the elasticity of the jar, so the shape of the jar, after its increase due to the volumetric expansion of the products during the sterilization process, is restored upon cooling.

Whole-stamped cans do not have a seam. They are obtained by stamping on a special press (the body of the jar and the lid are stamped).

Characteristics of prefabricated cans are given in table. 6.

Mass production of cans is carried out on automatic lines, the productivity of which is very high - up to 300 cans per minute. On fig. 4 shows a diagram of an automatic tin can line.

1 and 1a - feeders; 2 - curly scissors; 3 - presses; 4 - pasting machines; 5 - disk shears; 6 - body-forming machine; 7, 10, 13, 16 - elevators; 8, 11, 14, 17 - heat; 9 - flange bending machine (flange); 12 - seaming machine; 15 - testing machine (tester).

According to the scheme, tin sheets are laid on the receiving platform of the automatic feeder, the sheets are fed by the feeder to the curly shears, where they are cut with a curly knife into curly strips. The use of a shaped knife reduces the waste of tin in the production of cans.

The cut strips are stacked in piles in the receiving part of the automatic presses. Two presses are installed in the line, on which bottoms and lids for cans are stamped from figured strips. They flow through the estrus to the curling disc, which curls the lids or bottoms (ends) and stacks them in piles. Subsequently, the stacks of ends are transferred to pasting machines. Two machines are installed in the line, which apply rubber paste to the ends. The pasting machine has a dryer in which the paste is dried and only the rubber base remains at the ends. After the pasting machine, the dried ends are transferred and placed in the receivers of the seaming machines. This completes the production of ends for cans.

The machines carry out the body of the can, soldering it, connecting it to the bottom and checking the finished can; machines work in the following order.

The feeder feeds sheets to double disc shears, on which the sheet is cut into rectangles according to the dimensions (blanks) necessary for the manufacture of the can body. These rectangular strips of tin are called blanks in factory practice. The latter are manually stacked in piles in the receiving part of the body-forming machine, where the body is molded, a longitudinal seam is formed, it is riveted and soldered with solder (40% tin and 60% lead). The soldered finished body of the can is lifted up by the elevator and sent along the chute to the flange-bending machine (flange), where the body is bent on both sides, i.e., it is prepared for connection with the bottom and the lid. The beaded bodies are transported by an elevator and a chute to a seaming machine. Previously, it was indicated that bottoms are placed in the seamer shop. After seaming, the manufactured cans are fed by the elevator through the chute to the testing machine, which is called in factory practice testor. The test is carried out with compressed air. If the can is sealed, then the air pressure in it does not change during the test period; if the can is not sealed, the pressure drops, and the machine rejects such a can. The cans that have passed the test are sent to the elevator and by chute to the packaging warehouse.

Metal tin cans are made mainly from tinplate - thin sheet iron, coated on both sides with a layer of tin (half). Some factories have recently started making cans from aluminum sheet and aluminum alloys.

Until recently, for the manufacture of cans, tinplate with a thickness of 0.24 to 0.32 mm was used, but in recent years, thinner tinplate with a thickness of 0.20-0.22 mm has been mastered. The use of thin tin can improve the quality of tin cans, reduce metal consumption by 12-16%, as well as reduce the power of electric motors by 10-12% and extend the service life of tin can equipment.

Depending on the thickness, the tin is divided by numbers. The plate number shows its thickness in hundredths of a millimeter. For example, tin plate No. 25 has a thickness of 0.24-0.27 mm, tin plate No. 28 - 0.27-0.30 mm, etc.

For the manufacture of cans, the following types of tin are used:

1. Hot tin plate, hot rolled and cold rolled first and second grade tin plating.

The amount of tin applied to 200 cm2 of the surface of the first class tin (or 100 cm2 of the sheet tinned on both sides) should be 0.39-0.45 g, of the second class tin - 0.28-0.38 g.

First-class tin is mainly used to make jars for canned crab, intended for very long storage.

2. Hot-tinned, cold-rolled tinplate, ZhK grade, first and second class for tin coating. Due to its good malleability, tinplate is widely used for the manufacture of one-piece stamped cans of various shapes and capacities. The possibility of producing this tin in the form of strips of various widths determines its rational cutting (stamping of cans and lids) with a minimum amount of waste.

3. White rolled tinplate, electrolytic tinned, varnished, first grade, class I SEL. This tin is made of mild carbon steel, coated on both sides with tin (coating thickness on each side of the tape 0.8-1 microns) and over the tin with varnish or enamel (dry varnish film thickness 8-12 microns).

The lacquer film must be resistant to pure (distilled) water, vegetable oil (at 120°C), 3% sodium chloride solution, 2% tartaric acid solution, 3% acetic acid solution and standard protein solution. (3% gelatin, 1% sodium chloride and 0.2% sodium sulfide). After 2-hour boiling of tin plates in any of the indicated solutions, the varnish film should remain intact and retain its gloss and elasticity.

4. Electrolytic tinned white sheet, unvarnished, first grade and first class. For 200 cm2 of the surface of this tin there should be 0.12-0.15 g of tin. This tin can only be used for the manufacture of stamped jars and lids, subject to the obligatory double coating of them on both sides with hot baked food varnish.

Aluminum cans are produced only from seamless aluminum sheets A-0 and A-00 or its alloys with magnesium and manganese, which makes it possible to reduce the thickness of the metal from 0.4 to 0.3 mm, since the strength of the alloys is higher than the strength of pure aluminum .

Aluminum and its alloys have the same corrosion resistance. The corrosion resistance of aluminum and its alloys is improved by electrochemical anodizing and subsequent varnishing with epoxyphenol varnish 3-30-59.

In foreign countries (GDR), black (without pewter) lacquered tin is also used for the manufacture of cans.

In the USSR, the production of canned fish in cans of lacquered black tin has been mastered at canning factories in the Kaliningrad region and should be used in other enterprises in the future.

During the sterilization of canned food, the protein substances of the fish are partially destroyed with the release of sulfur compounds, which interact with the tin coating (half) on the inner surface of the cans made of tinplate. As a result, tin sulphide (SnS) is formed on the inner surface of the cans in the form of a bluish tint. With increased porosity of the semidry, the formation of iron sulfide (FeS) is possible, which also causes darkening of the inner surface of the cans and even of a part of the product adjacent to their walls.

To prevent darkening of the inner surface of the cans, reduce the amount of tin passing into the product, and prevent corrosion of the cans, usually tin or finished cans are varnished, and tinplate is sometimes passivated.

The essence of passivation is to create a protective film of tin oxides on the surface of the semidry by treating sheets of tin or finished cans with a solution of an oxidizing agent - sodium or potassium dichromate and caustic soda. The protective oxide film is formed as follows. When a tin plate is immersed in an alkaline solution of an oxidizing agent (sodium bichromate), at first a certain amount of tin dissolves with the formation of stannite and sodium stannate:

Sn + O + 2NaOH -> Na25n02 + H20 Sn + 20-"r 2NaOH -> Na25n03 + H20

The stannite and stannate then react to form tin oxides:

Na25n02 + NaoSnOz -] - 2H20 -» ​​BnOg + SnO + 4KaOH.

As a result of supersaturation of the tin solution layer adjacent to the metal, crystallization centers are formed on the metal surface, which, growing, turn into a continuous oxide film. The protective oxide films formed under the action of oxidizing agents can be divided into three groups depending on the thickness:

Thick - clearly visible films with a thickness of more than 5000 A (1 mmk \u003d 10000 A);

Medium thickness - films found on metal in the form of "temper colors", with a thickness of 400 to 5000 A;

Thin - invisible films, detected only by indirect methods, less than 400 A thick.

Passive oxide films on tinplate belong to the third group of films - invisible films.

The process of passivation of tin (or finished cans) consists of the following operations: degreasing of tin or cans;

Actually passivation - immersion of tin (cans) for a few seconds in an alkaline solution of an oxidizing agent;

Rinsing passivated tin (cans) with cold and then hot water to remove the passivator solution.

Passivation is a simpler and cheaper way to protect tin from corrosion than coating with varnishes and enamels, it significantly increases the resistance of cans to corrosion and in some cases can significantly reduce the tin content in canned food.

One of the new ways to protect cans from corrosion is to apply thin invisible layers of oil lubricant to their surface with the addition of surfactants (0.9-0.1%). The lubricant is applied to the cans in a high-voltage current field in a special chamber. This method of protecting cans from corrosion was developed by TsNIIChermet.

Cans used in fish canning (Fig. 11), depending on their shape and method of production, are divided into five types:

/ - cylindrical prefabricated (with or without a turnkey tongue);

II- cylindrical one-piece stamped;

III- figured one-piece stamped rectangular shape;

IV- figured one-piece stamped oval;

V - figured one-piece stamped elliptical shape.

Characteristics of cylindrical cans are given in table. 14, and figured one-piece stamped - in table. fifteen.

Table 14

For prefabricated cans with a tongue located on the body, the size I can be 4.8-5.0 mm larger than the size indicated in Table. fifteen.

For jars with a capacity of 96 to 250 ml, a capacity fluctuation of ± 1% is allowed, for jars with a capacity of 250 to 1000 ml - ± 0.5% and for jars with a capacity of 1000 ml - ± 0.25%.

Whole-stamp cans have only one seam at the junction of the body and lid, while prefabricated cans have three seams - one along the body of the can and two at the junction of the body with the ends (lid and bottom) of the can. Rice.

A longitudinal seam on the body of prefabricated cans is made

To the castle. It consists of four layers of tin (Fig. 12) and must be deepened inside the case and evenly soldered with an alloy of tin (40%) and lead (60%) to ensure the tightness of the case.

For fully stamped cans, the lids, and for prefabricated cans, the bottoms and lids are connected to the body with a double seam, which is a strong tight connection between the lid flange and the can body, consisting of five layers of tin with a layer of sealing material.

As a sealing material, paste is most widely used; rubber rings are also used for figured cans.

Paste with the help of special paste machines is applied to the pre-curved (twisted) ends of the cans. After drying, it is a thin elastic film, which fills the gaps in the seam during the canning process.

The film of the paste should not change during sterilization, should not color the contents of the jar and impart extraneous taste and smell to it.

And scald the ends of the cans covered with paste before use, and therefore are usually limited only to rubbing them.

In addition, during the steam exhaustion of cans filled with the product with pre-rolled lids, the aqueous ammonia paste swells and, during the final seaming of the cans, can flow out of the seam, which leads to a violation of the tightness of the cans and contributes to the spoilage of canned food. These shortcomings are devoid of vulcanized paste.

At the ends of the cans there is a corrugated relief, which ensures their elastic deformation during the sterilization of canned food. The shape and dimensions of the relief depend on the configuration and dimensions of the cans, as well as on the thickness of the sheet.

The bottoms of prefabricated cans are marked on presses during their manufacture in can shops. When marking the bottoms, the letter P is applied - the index of the fishing industry, the number assigned to the canned food factory (for example, 144 - the Temryuk fish cannery), and the last digit of the year the canned food was manufactured.

The marking on the bottom of the P1446 can indicates that the canned food was made by the fishing industry at the Temryuk Cannery in 1966.

The lids of the cans are marked on marking machines immediately before the capping of the filled cans. On the covers indicate the serial number of the work shift, the date of manufacture of canned food - the day and month and the assortment sign of canned food.

The month is conventionally denoted by letters of the alphabet: January - A,

February - B, March - C, April - D, May - D, June - E, July - F, August - I, September - K, October - L, November - M, December - H.

Assortment signs of canned food are indicated by numbers; the only exceptions are the assortment signs of canned food from the Far East salmon fish, flounder and sardines.

The marking inscription on the lid of the combined can 214B051 should be read as follows: second shift, March 14, carp in tomato sauce (assortment mark of this canned food 051).

At canning factories that do not have canning shops, as well as on trawlers and other ships that receive empty cans from enterprises, the markings on the lids are affixed in the following order: plant or trawler number, year of canned food production, shift serial number, canned food production date (date and month), assortment sign (number) of canned food. In this case, it is allowed to apply markings in two rows.

Marking on the lid of the can 457

455216IG or --------- denotes: 45 - Kikhchik fish factory

Combine, 7 - 1967, 2 - second shift, August 16-16, G - natural chum salmon in its own juice.

Whole-stamped cans for canned fish are labeled in the following order. When stamping cans, only the letter P is stamped on the bottoms - the index of the fishing industry; and the rest of the markings - the plant number, the last digit of the year of manufacture and others are applied to the covers in two rows.

Marking inscription on the cover of one-piece stamped 1336

At the Makhachkala fish cannery (factory number 133) in 1966 (6); the bottom row - in the first shift (1), January 14 (14A), Caspian sprats with spicy salting (192 - canned food assortment mark).

On the lids of cans of canned crab, produced in export clearance, they stamp or apply thermal

Resistant quick-drying paint the following markings: the first - the number of the floating cannery; the second - the last digit of the year of production of canned food; the third - F or A - the symbol of the variety of canned food; the fourth and fifth are the serial number of the day of production of canned food from the beginning of the season of the given year. The marking on the lids of crab canned food of the highest grade 45F62 or the first grade 41A62 indicates: 4 - floating cannery "Vsevolod Sibir

Tsev"; 5 - canned food produced in 1965; F - canned food of the highest grade (Fancy); A - canned food of the first grade (Agreid); 62 - canned food was produced on the 62nd day from the start of the production of canned crab at the Vsevolod Sibirtsev plant in this year.

On the bottom of the cans of canned crab, USSR signs are stamped - canned food is produced in the USSR.

Symbols (numbers) of canning enterprises and assortment signs (numbers) of canned food indicated during marking are unified and approved by leading economic organizations.

Before being put into production, cans are inspected and checked for leaks. On examination, jars with the following defects are rejected: tin influx on the longitudinal seam near the fold; the fold of the body of the can is large; the fold of the can body is bent; oblique can body; the fold of the body of the can is not bent enough (high fold); the shape of the fold circle is deformed; dented flanges or jar body.

Cans with burrs and notches along the fold, rusty and with protruding paste along the seam of the bottom seam are also not allowed into production.

The diameters of the ends and bodies of the cans must exactly match the dimensions established by the standard, otherwise the wrong seam will result when the cans are seamed.

The main requirement for the quality of cans is their tightness.

Banks are checked for leaks on automatic or semi-automatic testers, which are water and air.

In water testers, the test cans are placed in a tank with water and filled with compressed air at a pressure of not more than

1 ati. At the same time, leaky cans are easy to detect by air bubbles escaping through leaks in the seams.

Water testers are very reliable, but their productivity is relatively low, so they are used mainly for selective control of the tightness of cans and periodic control of the operation of air testers.

Air testers are high-performance automatic machines that allow you to control 100-120 cans per minute. With their help, you can check all the cans for leaks.
in the canning industry. A well-adjusted air tester will reject cans that pass more than 8-10 cm3 of air in 30-35 seconds.

With the advent of household can seamers, we all have the opportunity to cook stew, canned fish and other homemade preparations in cans. Of course, for this we still need an autoclave.

Types of cans

Few people use cans for canning, so people's ideas about them are very superficial. Let's try to fill this gap. We will not go into much depth, we will focus only on the main points.

So, what types of cans are there?

By design, tin cans can be divided into seamless and composite. In seamless cans, the bottom and side surface are a single whole, they are drawn from a single sheet of tin (hence the name). Only the cover rolls up. As a rule, seamless cans are cans of small height. Composite cans have three parts: a bottom, a side surface (body) and a lid. The bottom is the same lid that is rolled to the side surface at the can manufacturer. Moreover, as a bottom, at the request of the customer, both a standard lid and an Easy Open lid (easy to open) can be rolled on.

Composite cans, in turn, can be divided into welded and brazed. The side surface (body) of composite cans is made from a sheet of tin, which is bent into a cylinder, and then welded or sealed. Visually welded cans have a neat, beautiful weld. The solder seam is not so even, often with solder influxes. All modern manufacturers of cans make only welded cans. Soldered is an outdated technology. In Western countries, they are recognized as harmful and dangerous for food products, and are prohibited from production. There is no such ban in our country, therefore, when you go to any store, you can see canned food in such jars. All this is a legacy of the Soviet period: at large canning enterprises, lines for the production of brazed cans have been preserved since those times.

According to their design features, tin cans can still be divided into smooth and zig-zag (with ribs). The higher the bank, the more often zigovka is used on its lateral surface to give greater rigidity.

And, perhaps, the last constructive feature is the type of bottom: straight or narrowed. Banks with a narrowed bottom appeared much later. They are very convenient in terms of storage and transportation of finished canned products.

Now it's time to talk about the geometric dimensions of cans. Tin cans have their own GOSTs, for example GOST 5981-88. In accordance with GOST, each jar is assigned a number, for example, No. 9, No. 46, and also indicates the diameter, height, volume and other parameters. The most commonly used cans of the following diameters: 72.8 mm (cans No. 22, No. 4, No. 7, No. 9, No. 46) 83.4 mm (cans No. 5, No. 6, No. 38), 99 mm (cans No. 2, No. 3, No. 12, No. 13). This is the inside diameter. The outer diameter of the can is always slightly larger. It happens that they indicate: bank No. 9 72.8 mm or bank No. 9 76 mm. No need to think that these are different cans, just different diameters are indicated: internal and external, respectively. For cans of different diameters, when seaming, you need your own equipment for seaming machines. This should be taken into account when purchasing seaming equipment. The height of the can in this case does not play a role.

And in conclusion, a few words about covers. As already mentioned, there are standard lids and Easy Open lids that open easily without using an opener. To seam these caps, you also need your own equipment for seaming machine. In addition, Easy Open covers from different manufacturers differ in geometry (of course, there are the same ones), and each of them needs its own equipment. Therefore, if you plan to use Easy Open lids, you must first decide on the supplier of these lids, and only then buy a can seamer.

Since ancient times, people have faced the question - how to save food from spoilage? Over time, the problem became more global. Food had to be learned to preserve in large volumes (for expeditions and armies).

The very first canned food made by man was discovered during excavations of the tomb of Pharaoh Tutankhamun in Egypt. Products were in the depths of the earth for about 3000 years. They were ducks roasted and embalmed with olive oil in a clay bowl, the parts of which were held together with a resinous substance. These canned foods have withstood the test of millennia and were even fit for food (there is evidence that these ducks were fit for animal feed). Many of the modern ones can envy these canned goods.

Mark Porcius Cato the Elder (Roman senator) was one of the first "canners". In his work “On Agriculture” there was a note: “If you want to have grape juice all year round, then pour it into an amphora, grind the cork and lower the amphora into the pool. Take it out after 30 days. The juice will stand for a whole year ... "

In the year 63 of the 18th century, Lomonosov, organizing an expedition to explore the polar regions and the Northern Sea Route, made an order: "Making dried soup with spices and without spices, one and a half pounds of each variety." That is, 200 years ago, the soup concentrate traveled across Russia by land and the Arctic Ocean right to Kamchatka.

In 1795, about to take over all of Europe, Napoleon Bonaparte announced that a cook who could find a way to keep food fit for a long time would be paid 12,000 francs.

Disagreements between two scientists, Needham and Spallanzani (the first insisted that microbes appear from inanimate matter, and the second said that all microbes have their progenitors) led, completely far from science as such, the French culinary specialist Nicolas Francois Appert to idea - products, hermetically packed and subjected to heat treatment, can be stored for a long time. Apper turned out to be right, and his products prepared in a special way, having experienced long-term storage, were recognized as high-quality.

Upper spent 10 years proving the well-known fact today that the contents of jars filled with jam or soup do not deteriorate and remain good for a year if they are tightly corked and boiled in water for a long time. His invention was immediately put on stream for the warring French army.

Apper was rewarded for his invention with a state prize in 1809 and awarded the title "Benefactor of Mankind". He later opened his own business. The store was called "Miscellaneous food in bottles and boxes." There, Apper sold hermetically sealed ones made by him. The store had a small factory for the production of canned food. After that, Upper wrote the book "The Art of Preserving Plant and Animal Substances for a Long Period".

Scientific confirmation of Apper's ideas came only after 60 years. In 1857, at a meeting of the Society of Naturalists, Louis Pasteur, then an unknown scientist, made a work that there are microbes in the world that cause the processes of rotting products. To maintain the life of these microbes, certain conditions are needed - the level of temperature, high humidity, the presence of oxygen and, the most basic condition, the absence of antibiotic substances in the product. If these conditions are violated, the microbes will die. It is on this principle that the methods of preserving products are based - sterilization and pasteurization.

Although the Frenchman was the first to discover the method of long-term storage, another person, the Englishman Peter Durand, brought him to mind. Peter Durand patented tin cans, the familiar canned food that was much more convenient to use than glass bottles. Of course, they were very different from modern ones. The production was done by hand, besides, the jars had an inconvenient lid. Since 1826, England supplied the army with its own canned meat. But in order to open such banks, the rank and file were forced to use a hammer and chisel.
However, the palm in the production of canned food was taken not by France and England, but by the USA, where production began on the creation of machines designed for the manufacture of various cans.
Since 1819, in America they began to produce canned products from lobster, tuna, they also began to preserve fruits. It was here that tin cans acquired the form that we see to this day. Everything went very well. Canned food was in great demand, and they were literally swept off the shelves. Well, in 1860 a knife for these cans was invented. Again in the USA.

In the Russian state, of course, they knew about the innovation of the French. In 1821, the St. Petersburg and Moscow public debated animatedly about an extract from the Russian Archive magazine. It said that the turtle soup, which was poured into cans, was safely brought from the East Indies to the shops in London. However, despite this, the first canned food factory appeared only in 1870. The main customer, of course, was the army. Produced canned food in St. Petersburg. There were 5 types of them: fried beef, stew, porridge, meat with peas and pea soup.

On the 200th anniversary of the invention of the tin can, the Japan Canning Society has produced a unique batch of canned food. They reliably repeat those canned food that Napoleonic soldiers ate. In particular, the Japanese made again 5 varieties of canned food according to the recipes of Apper himself. In particular, the Japanese made a soldier's consommé, vegetable stew, pot-au-fee soup, melange of beans with champignons and a strawberry dessert. They were ceremonially opened and eaten at the headquarters of the Tokyo Canning Society.

Today's canned food, which is the diet of astronauts on the orbital station, of course, differs from the old army rations. Today they are unlikely to remember the Frenchman Apper, opening another tube of food, but the importance of canned food in our lives will not decrease from this.