Leather is available in many weights, textures, colours, and finishes.
Any skin can be made into leather – globally the following are used: Cow/calf 64%; sheep 14%; pig 11%; goat 9%; exotics (e.g. crocodile, alligator, ostrich, snake and fish) 2%.
Types of tanning
Tanning stabilises the protein of a raw hide or skin so it doesn't putrefy. The two most common types of tanning are:
This creates a soft and supple leather that can be dyed to almost any shade. It is the main type of leather used and comprises 80-90% of global leather supply. It is also known as wet-blue due to the chromium sulphate colouring the leather. Hides are placed in huge drums of tanning solution and agitated. The process takes 24 hours.
This uses ground bark such as oak or chestnut, which is soaked in cold water. Hides are hung in deep pits of the tanning solution then removed from the pits and layered with oak bark. The process takes 12-14 months in total. The leather produced is usually quite thick/hard and durable. The finished colours are usually a range of warm rich browns.
Chrome leather tanning involves chemicals, chromium and a lot of water. Some types of chromium used can have a detrimental effect on the environment when they are released from tanneries untreated. However, updated regulations and wastewater treatment systems have improved many tanneries.
That said, leather is still very resource intensive to manufacture, therefore it is best to get as much wear out of your leather items as you can and look after them to prolong their life.
Structure of Leather
The grain and the corium of the skin/hide is used to make leather. The corium thickness increases with an animal’s age, so calfskins are thinner, smoother and softer than the hides of mature cattle such as male bulls.
Thick hides are usually horizontally split through the corium to give several layers of leather:
• Top layer: Grain split leather
• Lower layers: Flesh split leather.
Types of Leather
Full grain leather
The grain gives leather strength, durability and breathability. It develops a patina during its lifetime.
Available in three finish types:
• Aniline: You can see the hide’s natural surface/grain.
It has either no surface coating or a very light surface coating to enhance its appearance and offer slight protection against spillages and soiling. Top quality hides are used.
• Semi-aniline: Has a light surface coating of polymer/pigment, which gives consistent colour and some stain resistance. More durable than aniline but still has a natural appearance.
• Pigmented: Has a polymer/pigment coating so you can’t see the natural grain of the leather. Less natural in appearance but very durable as it is fairly resistant to staining.
Imperfections are corrected or sanded off, an artificial grain is embossed into the surface and the leather is dressed with stain/dye.
Finished split leather
Uses the middle or lower section of a hide. A polymer coating is applied and embossed to mimic a grain leather. Should only be used in low stress applications as it is weaker than grain leather.
Other commonly available leather types
Bonded - Man-made reconstituted leather - leather fibres and a polyurethane binder are mixed and the surface is finished with a leather-like texture. Often used for lower quality garments.
Composition - Man-made leather - recycled leather shavings/grindings from the manufacturing process are bonded to a fabric layer. The surface is finished with polyurethane.
Nappa - The general term for soft, chrome tanned smooth leather of all animal skin types.
Nubuck - Aniline leather which has been lightly buffed on the grain surface to create a velvety finish. The nap is very fine because of the tight fibre structure in the grain layer.
Patent - A high gloss and shiny leather.
Sheepskin – The sheep wool is left on the hide making it warm to wear. Used for coats, gloves, slippers.
Suede - A split leather which has been ground to create a distinctive surface. It is usually very soft and malleable and therefore good for garment making.