Hide nation are not a tannery but offer these facts on hides and leather production.

To most people ‘leather is leather’. However if you think about the different uses for leather you will realise that the leather used for a handbag would be very different from the leather used in a luxury car. Even the leather used on furniture is unlikely to have the intensive wear and environmental challenges required of automotive leather.

Automotive leather has to withstand the wear and tear of clothing plus the effects of skin oils, sweat and even hair preparations in addition to the different temperatures and climate conditions across the world.

The development and production of automotive leather is a specialization, and different types of leather are required for each type of vehicle. Leather used for a sports model with a firm seat that grips the driver is different from a luxury limousine. Automotive leather requires a high degree of knowledge and craftsmanship to transform it from a natural product into a high quality interior.

Leather for automotive interiors comes mostly from cattle. The age and heredity of the animal and environmental conditions can affect the hide. Leather is a by product of cattle reared for the beef industry and would otherwise be wasted.

HIDE TYPES AND FINISHES

Pure Aniline
Pure Aniline is considered to be the finest hide available. Over the years Pure Aniline develops a patina which makes it desirable amongst leather aficionados.
Full Aniline
These are also some of the finest hides. The difference is that there is a smaller selection of hides available. To increase serviceability a slight protective finish is applied by roller or in the tannage to give the leather increased life .
Semi Aniline/Aniline Plus
These leathers have a little more processing. They are dried by aniline dying in large drums and then have a surface finish. Colour pigment sprays are applied to camouflage natural occurring imperfections.
Semi Aniline/Aniline Plus leathers are light and scratch resistant and are easily cleaned.
Corrected Grain Leather

These leathers undergo more processing including sanding, buffing, embossing and pigmenting, to cover natural imperfections. Barbed wire scrapes, insect bites etc, are removed to form a uniform thickness by sanding. Top grain leather is from the top 0.9 mm to 1.5 mm of the outer of the leather hide.

Top Grain Leather

This is not ‘top’ is the usual sense of the word. Top grain leather had the surface sanded away and a new grained surface is embossed onto surface.

Full Grain Leather

This leather retains the natural markings and grain patterns from the animal. Transparent aniline dyes are used to provide colour whilst still showing the natural grain. Full grain leathers are usually soft and supple and used in high quality upholstery.

 

THE TANNING PROCESS

Rawhides

· Hides are about 70% water and become hard and inflexible after drying.
· They can be easily attacked by bacteria and rot if not kept refrigerated or the water content removed
· Hides are contaminated and dirty with blood, dung, hair etc.

Leather for automotive interiors should be:
· Dry, flexible and stable
· They should have colour, softness and durability

Tanning makes the leather resistant to bacteria. Chrome tanning is the most popular method. The modern leather processing can be divided into three parts:

1. Preparation of wet blue.
2. Modification of the properties as needed in the final leather.
3. Finishing on the surface.

The processes in 1 and 2 are usually done inside drums in water. A few operations are carried out in special machines on individual hides/skins Preparation of wet blue Hides are washed with water and special detergents. This is known as Soaking. Hides are scrapped of any loose flesh. This is known as Fleshing. Hair is removed from the hide using special chemicals

The chemicals used in tanning modify the colour, softness and other properties. The fibre network should be opened up and most other non-fibrous material removed. This is done in Liming. This requires a special soaking which uses lime to increase the water entering the fibre network. Natural grease is also removed.

Hides are normally split into two layers. This creates a uniform thickness. The top layer is used for upholstery. The bottom layer is of non-uniform thickness and processed for different uses.

Adjustments in the acid/alkali balance (pH) of the hide are made before applying the chrome tanning salts. These operations are called Deliming and Pickling.
The chrome tanning salts react chemically with the molecules, making the fibre network resistant to bacteria. Modification of the final characteristics are made as required for the final leather product.

Modification of the leather
The main characteristics of the modified leather are:
· Leather Thickness
· Colour
· Softness

A number of other characters can be changed depending on the type of the leather being made by using specific chemicals.

After adjusting the pH balance, further chemical treatments are carried out.
Retanning uses special materials to change a range of characteristics. Dyes colour the fibres of the leather and oils are used in fatliquoring to soften the leather. Waterproofing, flame proofing, solvent resistance etc. can be applied at this stage.
The leathers are stretched and flattened in Setting Machines and then dried. The dried leather undergoes a number of mechanical processes to make it soft, flat and tight.
Surface finishing
A variety of finishing operations is carried out on the leather. Coating with coloured mixes is the most commonly used.

PRODUCTION PROCESS

Hides are sliced to a uniform thickness on precision machines. Only the surface is used. The lower splits are weaker and are subject to stretching and therefore provide an unstable base which results in cracking of topcoat finishes. The ‘chamois leather’ used for window and car washing is an example of split leather.

Hides are produced in many countries — the following list is a guide only of the grading structure used at the tannery level and are not quality grades used by manufactures.

A. Southern Germany, Switzerland, Northern Italy, Norway and Finland.
B. Northern Germany, England, The Netherlands and North America.
C. Australian, Africa, South American and Asia.

North and South America are the largest supplies of hides