How much do you know about leather

In general, the one with her teachings and the one with her teachings. Leather is the animal skin that has changed its original properties and is not perishable after physical and chemical processes such as hair removal and tanning.

1. How to classify leather:
1. The definition of leather: The leather that is taken directly from the animal and undergoes simple processing is called rawhide, and the rawhide has been processed. It is made of leather through various physical and chemical processing methods.
2. Types of leather: Basically, the types of leather are divided into two categories: leather and fur (velvet). In general, leathers commonly used in making shoes are cowhide, sheepskin, and pigskin. This leather is produced by removing the hair on the surface through a hair removal process. Another kind of suede (fur) is to keep the original fur quilt over timeaccording to the production process. The most common are suede, rabbit fur, horse hair and so on.
3. Tips for Identification
1) Hand touch: Touch the leather surface with your hands, and the hand feeling is usually smooth, soft, plump and elastic. The surface of synthetic leather generally feels astringent and is poorly soft.
2) See: There are small pores on the surface, and the texture is naturally irregular. The artificial leather surface has no pores and the texture is standardized.
3) Fire: There will be a smell of leather after being lit. The imitation leather has a pungent smell and forms lumps after ignition.

2. Classification of leather:
1. According to the source type and price of raw leather:
1) Leather: mainly kangaroo, lizard, real falcon. Crocodile skin and ostrich skin are natural animal skins, which are basically not modified during the production process to preserve their natural beauty. It cann rise during wear, which is a characteristic of leather and is unavoidable. In particular, the crocodile leather cover sheet can be bent when touched (that is, twisted when worn normally), which is the growth characteristic of crocodile leather, and it should not be bent toward people, otherwise cracks will appear.
2) General leather (): Also called natural leather, the leather surface is plump, with natural grain and fiber.
① Cowhide: Cowhide has fine pores, fine grain, irregular arrangement of pores, low elongation, high strength, soft surface and elasticity, and is most suitable for making shoes; there are buffaloes, yellow cattle and yak leather. they are mostly buffalo and yellow cattle, and the grain surface of yellow cowhide is more obvious than that of buffalo leather, and the surface is plump.
× Yellow cowhide: small pores, fine grain, thin surface, soft, good handfeel, high tensile strength, uniform thicknessof each part, small part difference, so the utilization rate is high. The pores on the surface are round and extend straight into the leather. The pores are tight and uniform, and the arrangement is irregular, like stars;
× Buffalo leather: thin and coarse hair, large and thick, it is hard and heavy easily, but the fibrous tissue is loose and the elasticity is not good . The pores on the surface are larger than that of yellow cow leather, the number of pores is larger than that of yellow cow leather, and the leather quality is looser, but not as fine and plump as yellow cow leather.
Most buffalo leather is produced in tropical regions, the large and rough leather structure makes it more suitable for furniture leather. Calfskin usually refers to cowhide born less than a year ago and is commonly used in footwear. Combined with a vegetable tannin treatment, it has become a very popular variety in recent years, such as waxed leather.
× Yakleer: thick plush hair, loose fibrous tissue and large differences in parts. Compared to yellow cowhide, the fibers are thinner and slightly softer, second only to yellow cowhide.
②Sheepskin: Sheepskin is light, thin and soft and is an ideal fabric for leather garments; the pores on the surface of the leather are flattened and clear, and several strands form a group, arranged in the shape of fish scales soft, plump and weak in strength For cowhide, there are sheep leather and goat leather. The former has a brighter grain and a fuller surface than the latter.
× Sheepskin: dense wool, thin skin, relatively low tensile strength, high elongation; high fat content, so the finished leather is soft and comfortable.
× Goatskin: The appearance is similar to raw woolen sheepskin, with a smooth and delicate weeping surface. The cellulose is thicker, the weaving is firmer than sheepskin, the finished leather is soft and stretchy, the neck and abdomen have a largeoot difference in thickness and the sheepskin is more resistant to folding
③Pigskin: pigskin has good water permeability and air permeability, and the leather surface The pores of the leather are round and thick, extending obliquely into the leather. The pores are arranged in groups of three, and the leather surface shows many small triangular patterns, showing the shape of a \"pin\". The leather surface feels worse than cow and sheepskin.
④ Horse leather: The pores on the leather surface are also oval, which is smaller than the pores of yellow cow leather. The arrangement is more regular.
3) Other processing categories:
× Oil leather: made of cowhide soaked in oil, it has a certain water resistance, soft and elastic. Some hiking boots or boat shoes often use oily leather. When the leather is stretched with nails or hands, the color lightens or darkens, but returns to normal after being stretched with handshas been ironed out. Leather with a sticky and oily feel is called greasy skin.
× Waxed Leather: Vegetable-tanned or semi-vegetable-tanned leather that has been polished to give a discoloration and burnt effect, also known as waxed leather. The leather surface is waxed, waterproof and easy to clean, and the leather surface is smooth.
× Nubuck leather: The cowhide leather front is polished, soft and wrinkle-resistant.
× Crazy Cow Leather: Nubuck leather soaked in oil, soft, wrinkle-resistant and to some extent waterproof.
× Litchi leather: The cowhide surface is pressed in a lychee pattern, which is beautiful and wrinkle-free.
× Imitation buckskin: Cowhide is made of leather as soft as buckskin Benefits: soft, light and comfortable.
× Polished leather: Using the traditional leather treatment method, use casein as the surface coating, and then use the glass roller to repeatedly polish the leather surface to achieve an elegant transtransparent shine. This type of leather is called polished leather, which is still treated in this way on calf, lamb and snake leather, is suitable for shoes. This type of leather has poor water resistance and is not suitable for outdoor shoes, especially for casual shoes. Shoe manufacturers in Europe still prefer smooth leathers for their bright and natural colours.
4)Artificial leather: based on textile, the surface is coated with chemical polyester. No natural grain (pores), most of the artificial grain (normal) has poor hand feeling and no fiber (a trace of very fine flesh), and there is imitation fabric on the back.
5) Synthetic leather: Basically the same as artificial leather, with a plump surface, natural grain, irregular arrangement and fibers on the back. All natural leather is stretchy, breathable and absorbent.
2. According to the application: shoe leather (upper leather, sole leather, shoe lininggs leather)
clothing leather, bag leather, glove leather, furniture leather, car seat
3. Cover by coating Possibility: Aniline leather finish
Semi-aniline leather finish
Surface finish
4. By Grain Surface: Full Surface (FG) Light Repair (SNUFF-BUFFED) Rebuild (CG)
5. According to commonly used varieties: Dye leather (full material surface, half-grain surface)
aniline leather (smooth leather, waxed leather, oil-washing, NUBUCK)
press (press) Pattern leather
Foil leather (including suede foil, shiny foil leather )
Patent leather
Suede
Double layer cow (SPLIT)

3. The production process of leather:
The production process of all types of leather are about the same. With cowhide as an example, the production process of cowhide is divided into the front part (water field) and the back part (dry field) two parts
1. Water field——The raw hides are converted into skin germs after the water field.There are mainly the following eight processes: (fur—wet blue leather)
1) Pre-soaking water: wash off the anti-corrosion salt and other sundries on the surface of the raw hide, dissolve the soluble protein in the hide, and apply the microstructure and the water content of the raw skin basically back to the state of fresh skin, and add an appropriate amount of preservatives, degreasers and immersion aids;
2) Main immersion: return to a suitable water content and expansion degree to ensure a good to achieve immersion effect, whether the immersion is good or bad and The quality of the finished leather has a lot to do with it: insufficient water immersion will lead to insufficient loosening at a later stage. Harden the finished leather board and excessive water immersion will cause the leather to loosen the surface; this time lasts 1 day and the water temperature is 20°C;
3) Hair removal: methodsinclude alkaline hair removal, enzymatic hair removal and hair removal by oxidation;
4) Limening: The process of treating raw hides with an alkaline solution consisting of lime and sodium sulfide, with the aim of swelling the bare skin and loosening the tissue structure of collagen fibers to be made;
5) Descaling and softening: the naked skin is treated after scaling In the state of expansion, there is a large amount of ash and alkali in the skin, which is not conducive to subsequent processing . bald skin is descaled to remove the ash and alkali in the skin, and then add descaling agent and degreasing agent for treatment. Using the catalysis of enzymes, the remaining hair roots, epidermis, hair root sheaths and pigments are removed, the collagen fiber structure is completely detached, and the elasticity, cleanliness and smoothness of the skin are improved;
6) Pickling and removalAcid: adjust the pH value of the bare huid, add diluted sulfuric acid to make the pH value of the water bath between 2.5-3, so that it is suitable for tanning
7) Chrome tanning: add tanning agent to the water bath to treat rough skin put into boiled leather (wet blue leather);
8) Dyeing part: The dyeing part is carried out in a drum, which mainly consists of:
＊squeeze the blue skin and peel it evenly (Hopu)
＊middle and re-tanning, dyeing, filling and greasing
＊stretching, vacuum cooling, moisture regain, softening, stretching and trimming
The whole dyeing process depends on the thickness of the leather, and takes about generally about 12 hours. Aihaoer anti-mold and anti-bacterial technology anti-mold Research Department (http://wzh1.com) reminds: If anti-mold function is required, an appropriate amount of AEM5700-PF leather anti-mold agent can be added to the greasing process
2. Dry field —— Raw hides are dyed and turned into skin germs,which are transferred to dry yards for further processing.
Dry finishing --- that is, to dry the leather through various drying methods (such as stretching, vacuum drying, hanging drying), this section also includes the preparatory work before painting, such as remoistening, softening, stretching , etc ;
Finishing---Leather finishing is the final modification of leather production, achieving the desired look, feel and physical properties of leather, it mainly includes grinding, spraying, embossing, softening and roll coating, Filling and other processes.

Fourth, the distribution of learning qualities:
According to the utilization rate of learning materials, the learning materials are divided into:
*: The utilization rate is more than 85 % Class B: occupancy rate 75%-85% Class C: occupancy rate 65%-75%
Class D: occupancy rate 55%-65% Class E: occupancy rate lower than 55%

5. Leather defects: divided into two types: natural defects and manufacturing defects:
1. Natural defects
Disabled (scratches, healed wounds, insect spots, gadfly\'s eye) raw veins and blood tendons
2. Defects in production
1) Loose surface: not tight, easy to wrinkle, and there will be grooves or wrinkles when the leather is pressed by hand. After recovery, it can be determined that the leather is a loose surface;
2) Flowering area and growth lines: Flowering area refers to an uneven color on a piece of leather, which usually occurs on full-grain waxed leather; growth lines are naturally formed Yes, it mainly occurs on the surface of waxed leather;
3) Tensile strength: the most common detection method is to cut a small hole with a knife at 2-75px from the line on the side from the back of the leather, then pull it gently with your index finger. Feel the tension; you can also test it with a professionalonal machine;
4) Color fading: there are two kinds of color fading: dry rubbing and wet rubbing, by rubbing the leather surface with a cotton cloth, you can see whether the color fades and whether the faded leather is completed Acceptable after no problem 5) Pu leather: different leathers have different thickness, sheepskin 0.6-0.8mm, and cowhide is generally 1.2-1.4mm

6. Factors affecting leather prices:
Demand and supply factors: Rare things are more expensive, and the price of calfskin has risen sharply Factors: There is only one style of this style;
Standard factors: Dynamic Waterproof 100,000 times; grade factor: nature is good;
production cost factor: more processes, more manual work, higher raw material costs; supply factor; ; Relational factors;

7. Leather care:
Leather care refers to the treatment of products, such as leather clothing, leatherrun sofas, leather chairs, leather bags, leather bags A series of care activities such as cleaning, maintenance, glazing, polishing and color addition of shoes, leather shoes, etc. restore the beautiful new appearance of the product and extend the life of the leather.

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