Leather

　　Animal hides that have been dehaired and tanned through physical and chemical processes, resulting in a denatured, decay-resistant material. Leather is composed of natural protein fibers tightly woven in three-dimensional space. Its surface has a unique grain layer with natural grain and luster, and a distinctive feel. It is often used to make fashion and winter clothing. It is divided into two categories: one is leather, which is dehaired leather; the other is fur, which is processed leather with fur still attached. Its advantages are lightness, warmth, and elegance. Its drawbacks are its high price and the high demands for storage and care, making it unsuitable for widespread use.

　　Humans primarily use raw materials from animals raised and slaughtered in their living environment for leather production. Leather materials range from commonly used cow, sheep, and pig hides to those of snakes, insects, birds, and fish, creating practical materials or decorative items. Examples include cowhide, water buffalo hide, pigskin, goatskin, sheepskin, lambskin, deerskin, kangaroo skin, snakeskin, ostrich skin, crocodile skin, and fish skin.

　　(I) Characteristics of Natural Leather

　　1. Relatively strong odor, thick (generally >1.0 mm), and durable.

　　2. Full of fine pores, good breathability.

　　3. Shows significant layering, in a transitional state.

　　4. Soft, lustrous, strong, and retains its shape after molding.

　　(II) Thickness Standards of Natural Leather

　　1. Thicknesses: 0.8-1.0 mm, 1.0-1.2 mm, 1.2-1.4 mm, 1.4-1.6 mm, 1.8-2.0 mm

　　2. Commonly used thicknesses: 1.0-1.2 mm, 1.2-1.4 mm

　　(III) Commonly Used Thicknesses of Natural Leather

　　1. Sheepskin: 1.0 mm and above

　　2. Cowhide: 1.2 mm and above

　　3. Pigskin: 0.8 mm and above

　　(IV) Common Types of Natural Leather

　　1. Cowhide: Full feel, dense texture, surface full of pores.

　　2. Korean Cowhide: Standard, appearance similar to cowhide (but darker and harder in color).

　　3. Cow Suede: Standard 1.05-1.7 mm, 1.6-1.8 mm, velvety feel, hard leather.

　　4. Cow Split Leather: The fiber layer after the top layer is removed; can be made into suede split leather, coated split leather, or dry PU split leather by applying a PU film.

　　5. Sheepskin: Fine pores, high value.

　　6. Pig Suede: Soft, hairy on one side, smooth on the other, clear grain, thickness around 0.8 mm.

　　7. Pigskin: Hard feel, indistinct grain.

　　(V) Leather Classification by Grain Type

　　1. Full-grain leather

　　2. Suede

　　3. Split leather

　　(VI) Leather Classification by Coating Type

　　1. Drum-dyed leather

　　Natural feel, no adhesives, resins, or coatings added.

　　Characteristics: Maintains natural style, but with significant color variations, poor stain resistance, and poor resistance to fire and solvents.

　　2. Dyed leather

　　No coatings added, maintains natural appearance.

　　Characteristics: Natural grain, but significant color variations remain, weak coating properties.

　　3. Leather-dyed leather

　　A small amount of coating is added to improve color variations and defects, while maintaining a degree of feel and transparency.

　　4. Coated leather

　　Primarily colored with coatings, significantly improving color variations and defects.

　　Characteristics: Grain is not natural.

　　5. Embossed leather

　　Can be any of the above four types of coating, but embossing improves or changes the grain.

　　6. Glazed leather

　　Glazed with a glass rod to create a smooth, fine grain. Casein can create a smooth, glossy, transparent feel, commonly used on small animal skins.

　　Characteristics: Transparent color, natural high gloss, high quality, but significant color variations, poor physical properties, visible grain, and deeper color in oily areas.

　　7. Buffed leather

　　Polished with a stone wheel or brush wheel to create a smooth, glossy surface, suitable for any type of leather.

　　8. Printed leather

　　Patterns are printed using rollers on any type of leather.

　　9. Oiled leather

　　Uses a large amount of oil to create a special effect, such as pull-up color-changing leather or an oily feel. Can be used on full-grain or nubuck leather.

　　10. PU Coating

　　Polyurethane is applied to the surface of the leather, creating a strong film on split leather, mimicking full-grain leather, increasing value, and providing good physical properties.

　　(VII) Characteristics of Different Parts of Leather

　　1. Butt: This is a delicate area.

　　2. Shoulder: Relatively soft, but usable.

　　3. Neck: Cowhide neck has strong tensile strength, but it is difficult due to growth marks.

　　4. Front and rear legs: The waist area of cowhide has more wrinkles.

　　5. Belly: A soft and durable area, but it has poor quality due to its extensibility.

　　(8) Classification of Natural Cowhide

　　1. Calf (newborn calf): 4-6 square feet, light

　　Characteristics: Very detailed epidermis, soft and elastic feel, suede is very soft.

　　2. Yearling (under 12 months): 11-14 square feet, light (medium)

　　Characteristics: Slightly rough skin, visible growth wrinkles, tough, elastic and full feel.

　　3. Immature yearling (12-18 months): 14-20 square feet, medium weight

　　Characteristics: The epidermis is coarser than that of a yearling, the fiber arrangement is loose, and it is easy to stretch.

　　4. Cowhide (1-3 years old): 8-10 square feet (half), medium weight, very strong and dense skin, suitable area for cutting.

　　5. Cow (over 3 years old): 11-24 square feet (half), heavy

　　Characteristics: Very rough, thick skin, visible scars. Such as: marks, insect bites, scratches.

　　6. Cow: 5-8 square feet, slightly thick

　　Characteristics: Strong skin, slightly prominent pores on the surface.

　　7. Goat: 4-6 square feet, light

　　Characteristics: Light and tough, suitable for dyeing.

　　8. Sheep: 2-3 or 6-8 square feet, light or medium

　　Characteristics: Soft, white skin, used in children's shoes or boots