Consideraciones del capítulo

Vegetable tanning uses tannin (this is the origin of the name of the process). The tannins (a class of polyphenol astringent chemical) occur naturally in the bark and leaves of many plants. Tannins bind to the collagen proteins in the hide and coat them causing them to become less water-soluble, and more resistant to bacterial attack. The process also causes the hide to become more flexible. The primary barks, processed in Bark Mills and used in modern times

are chestnut, oak, redoul, tanoak, hemlock, quebracho, mangrove, wattle (acacia;

see catechu), and myrobalan. Hides are stretched on frames and immersed for several weeks in vats of increasing concentrations of tannin. Vegetable tanned hide is flexible and is used for luggage and furniture.

3.Aluminium Tanning:

Tawing is a method that uses alum and aluminium salts, generally in conjunction with other products such as egg yolk, flour, and other salts. The leather becomes tawed by soaking in a warm potash alum and salts solution, between 20°C and 30°C. The process increases the leather's pliability, stretchability, softness, and quality. Adding egg yolk and flour to the standard soaking solution further enhances its fine handling characteristics. Then, the leather is air dried ("crusted") for several weeks, which allows it to stabilize. Tawing is traditionally used on pigskins and goatskins to create the whitest colors. However, exposure and aging may cause slight yellowing over time

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and, if it remains in a wet condition, tawed leather will suffer from decay. Technically, tawing is not tanning.^[10]

Depending on the finish desired, the hide may be waxed, rolled, lubricated, injected with oil, split, shaved and, of course, dyed. Suedes, nubucks etc. are finished by raising the nap of the leather by rolling with a rough surface.

The first stage is the preparation for tanning. The second stage is the actual tanning and other chemical treatment. The third stage, known as retanning, applies retanning agents and dyes to the material to provide the physical strength and properties desired depending on the end product. The fourth and final stage, known as finishing, is used to apply finishing material to the surface or finish the surface without the application of any chemicals if so desired.

3.Finishing.

For some leathers a surface coating is applied. Tanners refer to this as finishing.

Finishing operations may include:

 Oiling.

Oiling is a process whereby leather is hand coated (usually by brush or tampon) with either a raw (un-emulsified) oil or a combination of raw oil, blended with emulsified oils and a penetrating aid. Hand oils can include fragrant oils that help with the smell associated with the leather, e.g., Pine Oil.

Hand oils commonly consist of sulfated vegetable oils, e.g. sulfated castor oil.

Oiling provides the leather with lubrication and allows it to flex repeatedly without cracking. Leather fibres that are dry and un-lubricated break very easily. Oiling does impart colour and an element of water resistance. Oiling would normally be performed on full grain aniline leathers. The most common type of leather oiled is vegetable tanned leather.

 Padding.

 The padding clears an area around the content (inside the border) of an element. The padding is affected by the background color of the element.

 The top, right, bottom, and left padding can be changed independently using separate properties. A shorthand padding property can also be used, to change all paddings at once.

 Buffing.

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Leather from which the top surface has been removed by abrasion. Often known as suede or nubuc.

 Spraying. It’s a mixture of chemical season that mixed with water and applied on skin.

This mixture contain

 Pigment:

Its color solution that are applied on the top of skin.

 Dye solution

Its is another type of color solution.it depends on the article.

 Laker: It’s a chemical solution that fixing color.

 Curtain Coating is a process in which the object or substrate to be coated is Curtain coating.

guided through a curtain of fluid located in a gap between two conveyors. The mechanism is formed by a tank of fluid from which a thin screen falls down in between the two conveyors. The thickness of the coating layer that falls upon the object is mainly determined by the speed of the conveyor and the amount of material leaving the tank (Pump Speed). Curtain coating is a premetered

method, which means that the amount of liquid required is supplying from the tank to the screen in order to be deposited on the substrate.

 Polishing.

Polishing is the process of creating a smooth and shiny surface by rubbing it or using a chemical action, leaving a surface with a significant specular

reflection (still limited by the index of refraction of the material according to the Fresnel equations.)^.In some materials (such as metals, glasses, black or trasparent stones) polishing is also able to reduce diffuse reflection to minimal values. When an unpolished surface is magnified thousands of times, it usually looks like mountains and valleys. By repeated abrasion, those "mountains" are worn down until they are flat or just small "hills." The process of polishing with abrasives starts with coarse ones and graduates to fine ones.

Polishing with very fine abrasive differs physically from coarser abrasion, in that material is removed on a molecular level, so that the rate is correlated to the boiling point rather than to the melting point of the material being polished.

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 Plating.

Plating is a surface covering in which a metal is deposited on a conductive surface. Plating has been done for hundreds of years, but it is also critical for modern technology. Plating is used to decorate objects, for corrosion inhibition, to improve solderability, to harden, to improve wearability, to reduce friction, to improve paint adhesion, to alter conductivity, for radiation shielding, and for other purposes.

 Embossing is the process of creating a three-dimensional image or design Embossing. in paper and other materials.

Embossing is typically accomplished by applying heat and pressure with male and female dies, usually made of copper or brass, that fit together and squeeze the fibers of the substrate. The combination of pressure and heat raises the level of the image higher than the substrate, while "ironing" it to make it smooth.

In printing this is accomplished on a letterpress. The most common machines are the Kluge Letterpress and the Heidelberg Letterpress.

Most types of paper can be embossed, and size is not normally a consideration.

Embossing without ink, so that the image is raised but not colored, is called

"blind embossing." Embossing used in conjunction with ink, so that the raised area is colored, is called "color register embossing." Embossing used in conjunction with foil stamping is called "combination stamping" or "combo stamping."

Embossing involves a separate stage in the production process, after any varnishing and laminating. It requires a separate press run, and is priced accordingly. In addition to being used as a design element, embossing can be used to improve the performance of paper products like napkins, diapers, and tissue paper.

 Ironing.

Ironing is the use of a heated tool (an iron) to remove wrinkles from fabric. The heating is commonly done to a temperature of 180-220 °Celsius, depending on the fabric.^[1] Ironing works by loosening the bonds between the

long-chain polymer molecules in the fibers of the material. While the molecules are hot, the fibers are straightened by the weight of the iron, and they hold their new shape as they cool. Some fabrics, such as cotton, require the addition of water to loosen the intermolecular bonds. Many modern fabrics (developed in or after the mid-twentieth century) are advertised as needing little or no

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ironing. Permanent press clothing was developed to reduce the ironing necessary by combining wrinkle-resistant polyester withcotton.

 Toggle.

It’s a machine process by which skin is stretched.

 Measurement.

Its final stage of production where every skin are to be measure in decimeter.(dcm).

Production department works under instruction of managing director of the company Initially the process of leather skin that is raw material should follow the Ist stages. In that its conversion raw material to wetblue. (works in progress).

In 2^nd stages wetblue to crust. (semi finished goods). this semi finished goods can be sell in the local market based on measurement of skin in terms of dcm.(deci metre) per rate. Or the crust can be used for finishing stages.

The chief technician will recive a shade card. It’s a instruction from managing director about the article.

In the finishing stages based on the order and requirement from the buyers.they are taking the order. The requirement from the buyer are.

Article name: Nappa Quantity: 20,000 sqft.

Size: 0.6 mm.

Rate: 1.2 $.

4.2 INVENTORY DEPARTMENT.

In the inventory department is control under the managing director. Under inventory department there are two section.

1.Chemical section.

2.Skin Section.

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