YoSteve
09-14-2003, 03:26 PM
I was looking at Leather Tiles (floor and wall) and happened upon this read.
For those who don`t think leather is topcoated, at least one company "finishes" their leather.
Automotive
This leather has been specifically designed for use in the automotive industry.
Automotive is a high performance leather in full substance and tanned to superior specifications. It is best suited for upholstery and trimming in the auto and marine industries, where a high performance leather is required.
It can also be used in high traffic areas in commercial environments with additional treatment to Crib 5 standard.
Automotive leather meets the requirements of ISO/DIS 6452 preventing interior fogging of glass and mirrored surfaces.
The Leather Process
History of tanning
The process of tanning is one of the oldest professions in the world; its origins can be traced back to the Stone Age. Since the first century A.D. Leather has long been considered a luxury product and even today, it maintains worldwide appeal.
1. The leather making process:
Once removed from the animal the skin is left to cool. This initial stage is very important to prevent bacterial infection of the skin. These are then salted to preserve them and then they are shipped to the tannery for further processing.
There are three main stages involved in the production of leather:
(1) Rawhide
(2) Wet-Blue
(3) Finishing
1. Rawhide is the term for leather that has been cut from the carcass of the animal and then cured (usually with salt). When the leather arrives at the tannery, the skins still have fatty deposits attached to their underside to protect and aid in further evaluation of the hide.
These must now be removed. This process used to be carried out manually by laying the skin on a ‘beam’ and scraping the flesh off the skin with a sharp knife. This stage is known as the beamhouse process. Today this process is done more by machinery than by hand, ensuring more precision and a quicker turn around to the next stage of production.
Hide is essentially made up of interlocking fibres; the spaces between are filled with proteins, blood vessels, muscles and capillaries. To stop the skin from putrefying, all of these components must be removed. This process is achieved by liming.
In this process, the skins with original hair intact are loaded into a drum and spun with a solution of calcium carbonate or lime. This has the effect of hydrolysing or making the proteins including the hair, soluble. These components can now be “washed out†of the skin.
Excess lime must now be removed (Deliming). Once this stage is complete, further proteins can be removed using enzymes. This term is called bating. When all the proteins have been removed, the skin is treated to prevent it from degrading further. The most commonly used products for this process are Chromium salts. The leather now enters the next stage of production.
2. Wet Blue
Chromium salts are now soaked into the skins. The resultant product is known as wet blue, due to the colour achieved after this treatment. Now the leather can easily be transported and kept for many months before it starts to degrade.
While the leather is in the wet blue stage, it is then selected for quality. It takes for an experienced selector, to decide which hides are to be processed into first quality leather and which can be processed into lower selections. This is a vital part of the operation and is only carried out by only the most experienced personnel.
At this stage, the leather may undergo splitting, which is the process whereby hide is split into layers. Full substance wet blue is normally far too thick for most applications and so the splitting literally slices it into further layers.
After the splitting stages, the hides are often shaved. This involves a razor sharp machine that shaves the rear of the hide so that it has a consistency thickness throughout.
After shaving, the hides are now ready for the post-tanning operations. This involves the hides being placed back into large drums, where they are re-tanned and re-dyed. Here, complex dyes, fats and oils are added, these colour and lubricate the leather, making it even softer than previously. Modern computer controlled mixing systems are usedat this stage, to ensure constancy.
After removal from the drums, the hides are machine dried by stretching the leather with toggle pincers on to a screen, which is passed through a drying oven.
Once fully dry, the surface may be lightly buffed to remove any small surface defects that may have accumulated on the skin.
3. Finishing
The following example is for Pigmented Hides
The last but by no means least process is that of the finishing of the hide. The hides are fed through a spray machine that applies a fine mist of coloured pigment over the surface of the leather. The leather then passes onto a drying line, which consists of a long tunnel of ovens, which dry the pigment coat. Following this, the leather is usually embossed to give a uniform pattern. It is then given a durable topcoat to protect it from further wear and tear.
Before dispatch, it is often sent to be dry milled. This entails placing it into large drums that, by their mechanical action, pummel the leather. This further softens the leather.
Finally the leather is ironed to remove any creases and packaged ready for shipment.
For those who don`t think leather is topcoated, at least one company "finishes" their leather.
Automotive
This leather has been specifically designed for use in the automotive industry.
Automotive is a high performance leather in full substance and tanned to superior specifications. It is best suited for upholstery and trimming in the auto and marine industries, where a high performance leather is required.
It can also be used in high traffic areas in commercial environments with additional treatment to Crib 5 standard.
Automotive leather meets the requirements of ISO/DIS 6452 preventing interior fogging of glass and mirrored surfaces.
The Leather Process
History of tanning
The process of tanning is one of the oldest professions in the world; its origins can be traced back to the Stone Age. Since the first century A.D. Leather has long been considered a luxury product and even today, it maintains worldwide appeal.
1. The leather making process:
Once removed from the animal the skin is left to cool. This initial stage is very important to prevent bacterial infection of the skin. These are then salted to preserve them and then they are shipped to the tannery for further processing.
There are three main stages involved in the production of leather:
(1) Rawhide
(2) Wet-Blue
(3) Finishing
1. Rawhide is the term for leather that has been cut from the carcass of the animal and then cured (usually with salt). When the leather arrives at the tannery, the skins still have fatty deposits attached to their underside to protect and aid in further evaluation of the hide.
These must now be removed. This process used to be carried out manually by laying the skin on a ‘beam’ and scraping the flesh off the skin with a sharp knife. This stage is known as the beamhouse process. Today this process is done more by machinery than by hand, ensuring more precision and a quicker turn around to the next stage of production.
Hide is essentially made up of interlocking fibres; the spaces between are filled with proteins, blood vessels, muscles and capillaries. To stop the skin from putrefying, all of these components must be removed. This process is achieved by liming.
In this process, the skins with original hair intact are loaded into a drum and spun with a solution of calcium carbonate or lime. This has the effect of hydrolysing or making the proteins including the hair, soluble. These components can now be “washed out†of the skin.
Excess lime must now be removed (Deliming). Once this stage is complete, further proteins can be removed using enzymes. This term is called bating. When all the proteins have been removed, the skin is treated to prevent it from degrading further. The most commonly used products for this process are Chromium salts. The leather now enters the next stage of production.
2. Wet Blue
Chromium salts are now soaked into the skins. The resultant product is known as wet blue, due to the colour achieved after this treatment. Now the leather can easily be transported and kept for many months before it starts to degrade.
While the leather is in the wet blue stage, it is then selected for quality. It takes for an experienced selector, to decide which hides are to be processed into first quality leather and which can be processed into lower selections. This is a vital part of the operation and is only carried out by only the most experienced personnel.
At this stage, the leather may undergo splitting, which is the process whereby hide is split into layers. Full substance wet blue is normally far too thick for most applications and so the splitting literally slices it into further layers.
After the splitting stages, the hides are often shaved. This involves a razor sharp machine that shaves the rear of the hide so that it has a consistency thickness throughout.
After shaving, the hides are now ready for the post-tanning operations. This involves the hides being placed back into large drums, where they are re-tanned and re-dyed. Here, complex dyes, fats and oils are added, these colour and lubricate the leather, making it even softer than previously. Modern computer controlled mixing systems are usedat this stage, to ensure constancy.
After removal from the drums, the hides are machine dried by stretching the leather with toggle pincers on to a screen, which is passed through a drying oven.
Once fully dry, the surface may be lightly buffed to remove any small surface defects that may have accumulated on the skin.
3. Finishing
The following example is for Pigmented Hides
The last but by no means least process is that of the finishing of the hide. The hides are fed through a spray machine that applies a fine mist of coloured pigment over the surface of the leather. The leather then passes onto a drying line, which consists of a long tunnel of ovens, which dry the pigment coat. Following this, the leather is usually embossed to give a uniform pattern. It is then given a durable topcoat to protect it from further wear and tear.
Before dispatch, it is often sent to be dry milled. This entails placing it into large drums that, by their mechanical action, pummel the leather. This further softens the leather.
Finally the leather is ironed to remove any creases and packaged ready for shipment.