What is leather?

Raw Materials for Leather-Making

Difference between Rawhide and Leather

The pores on the surface of pig leather are mostly arranged in groups of three in a "pin" shape. Within each group, the middle pore is the largest and forms the smallest angle with the grain. The pores of pig leather penetrate almost the entire thickness of the leather, going deep. Since the pores of pig skin are larger than the fat cones formed by the meat surface layer, and the papillae on the papillary layer are prominent, the grain surface of pig leather is rougher. The subcutaneous fat tissue of pig skin is well-developed, and the subcutaneous fat cells extend into the dermis. After degreasing, the flesh side of the leather shows fat pits. Overall, pig leather exhibits significant differences among its parts. The buttocks are thicker, with collagen fiber bundles cross-woven, resulting in very high strength and low extensibility. The collagen fibers in the back, abdomen, etc., are obliquely interwoven, and their thickness and strength are not as good as those of buttocks leather.

The surface pores of yellow cowhide leather are small and dense, with gentle papillae and a fine-grain surface. The pores are oval, tight, and evenly distributed, arranged irregularly like a starry sky. The roots of the guard hairs grow deeper into the skin, while the roots of the down hairs grow shallower. The sweat glands are well-developed and located at the junction of the papillary layer and the reticular layer. The papillary layer and the reticular layer in the dermis are demarcated, with the papillary layer accounting for about 20%± of the skin's total thickness. The collagen fiber bundles in the papillary layer are thinner, while those in the reticular layer are thick and densely woven. Yellow cowhide leather has a large width, with relatively uniform thickness throughout each part, showing little variation.

Buffalo leather is wider, thicker, and more uneven than yellow cowhide, with coarse pores and an irregular dot arrangement. The papillae on the grain are tall, dense, and deeply wrinkled, giving buffalo leather a rough grain. There are numerous fiber bundles at the junction of the papillary layer and the reticular layer, which are firmly combined and have unclear boundaries, but the fiber structure is distinct. The collagen fiber bundles in the papillary layer are small, tightly woven, and relatively thin, accounting for about 4% to 12% of the total leather thickness; whereas the reticular layer is particularly thick, almost entirely composed of collagen fibers, with thick fiber bundles and loose weaving. The main direction of the fiber bundles is "head-to-tail."

The pores of sheep leather consist of pin pores and down pores. Several pin hairs and down pores form a group and are arranged in a semi-circular shape. There are more fat cells in sheep leather, with the lipid content accounting for about 30% of the cortex. The grain layer accounts for 50% to 70% of the dermis's thickness, and some even reach 80%. There are numerous tissues such as sebaceous glands, sweat glands, and hair follicles. The pores and papillae are small, making sheep leather feel more comfortable, soft, smooth, and delicate, with great extensibility. Due to its relatively loose tissue structure, the fiber bundles in the reticular layer are thinner and mostly parallel, resulting in sheep leather having lower strength than goat leather.

The pores of goat leather are small, oval, and evenly arranged in a corrugated pattern. They are generally divided into two layers: the outer layer consists of guard pores, and the inner layer consists of down pores. The guard hairs are arranged in groups of three, in a "V" or "pin" shape, forming the unique structure of goat grain pores. The fiber weaving of goat leather is relatively tight, and its grain roughness, smoothness, and feel are slightly inferior to sheep leather, but its strength is higher than sheep leather and lower than cowhide. The grain layer accounts for about 50%~70% of the dermis's thickness. The papillary layer in the dermis is densely organized, with low-fat content, and the reticular collagen fibers are also tightly woven.

Deerskin:

 Deerskin is thicker, with the grain layer being thicker than the reticular layer, and its grain resembles goat skin. Due to the presence of numerous glands such as sebaceous glands, the finished leather is soft. The pores are larger than sheepskin and arranged in a "V" shape. The angle between the pores and the grain is large. Deerskin is strong and has good extensibility.

Kangaroo leather:

Kangaroo leather possesses a unique fiber structure, and its entire skin is triangular. The pores are oval and distributed in irregular patterns. The collagen fiber bundles of kangaroo skin differ from those of typical mammals in their weaving pattern. Most of the collagen fiber bundles are parallel to the leather surface and woven in a wavy, layered fashion. Different layers are interlaced and interconnected, with an interlacing angle of less than 90° between them. The weaving pattern of collagen fibers remains consistent across various parts, with only slight differences in tightness. Generally, the buttocks and neck areas are thicker, while the abdomen is thinner. The grain layer of kangaroo leather comprises more than 70% of the dermis' thickness. The fiber bundles are exceptionally thick, originating from the epidermis. Due to the scarcity of sebaceous and sweat glands, the fibers are tightly bound together. Consequently, kangaroo leather exhibits exceptional physical strength, strong wear resistance, and high extensibility. Because the kangaroo pores are fine and sparse, the finished leather's grain surface is smooth and delicate.

The surface texture of crocodile leather is naturally beautiful, featuring large, nearly square scales that distinguish it from other leathers. The texture on the back differs slightly from that on the abdomen; the back scales are larger, and the back also boasts raised, hard, and prominent scales. Crocodile leather is sturdy, possessing a balanced hardness and softness.

The papillae on the grain of Ostrich bird leather are tall, with wrinkles of varying depths, rendering the grain surface rough. The pores are large and protruding, and feather holes penetrate the entire dermis. The grain surface exhibits a unique three-dimensional pattern. The collagen fibers of Ostrich bird skin are tightly woven, with elastic fibers sparsely distributed. The muscle tissue is thick, and the parts are widely differentiated; the neck and abdomen are thinner, while the buttocks and back are thicker.