All About Leather

custom leather interior

Some Examples of leather we have to offer when choosing your custom Leather interior.

Introduction To The Planning Process

Leather is the outer skin of an animal, which has been preserved by tanning into a flexible sheet. The process of tanning skin has been a well guarded secret over the ages, handed down from father to son until more recent times when modern manufacturing processes have demanded speedier and faster results.

Leather working is one of the oldest industries known to man and was probably started shortly after the first cave dwellers ate their first meal, Mans ability to adapt this waste by-product of his diet into assisting him to survive undoubtedly enabled him to develop faster than any other living creature on earth.

He used the skins as a secondary covering to keep himself warm, for strapping to enable him to carry and still use his hands, as a gourd for carrying water, thus extending his area of forage, as a sling, a crude weapon adapted to kill his food which in turn saved him energy that was previously expended in the hunting chase.

As man developed through the ages, so did the use of leather, from the original crude weaponry of the cave man to the sandals, clothing and armour of the Roman legions, from the harnesses of plough horses, to the drive belts of heavy machinery until we have seen it finally develop into the fashion items of today, ie. shoes, jackets, handbags,  furniture,car seating and accessories and more importantly to us the suppliers of the finest vehicle interiors in today’s modern world.

It is important to understand that a successful leather interior not only depends on the products and systems employed, but the ability of the designer and trimmer to recognise the type and condition of the leather to be worked with.

To get a better understanding of this natural product the designer or trimmer has to start at a point in time well before the beast was slaughtered.

For example:

What country did the beast originate from – was the climate hot, cold, wet or dry also was there enough natural forage for the beast to graze on.

What was the political climate like in the country of origin at the point of slaughter – in most recent times Eastern Europe, which has been a large provider of hides to the leather industry, has been in the throws of a vicious Civil War.  People have struggled to feed themselves let alone the cattle, therefore the well being of the beast would be greatly affected, which in turn would reflect in the condition of the hide.

The husbandry of the herd: regardless of where the beast originated from would also affect the condition of its hide.

Did the farmer keep the beasts clean, was the corralling and fencing of the farm in good order, what food was the beast fed on, how old was it when it was slaughtered, what sex was it, etc. etc.

All of the above are contributing factors to the finished product of leather and the type of finishing process that needs to be employed.

Moving on to the point of slaughter, it is interesting to remember that the beast has been slaughtered for its commercial meat value not for its hide.

The hide or skin at this stage is a waste product of the meat industry and is sold in general terms as offal not as a quality item and it is well worth remembering this point when starting to consider the skills and techniques employed by the tanner, designer and upholsterer.

For example, the commercial meat value of a cow has it’s value but the skin initially becomes a waste product until purchased buy the tanner.

The tanner will probably purchase the hide of that cow for a small fee and his skill and ingenuity will increase the sale value of that hide many times over.

It is at this point that the designer needs to understand the motive of the tanner and the reason why some tanning processes are jealously guarded secrets.

These days you are told whet the leather can be used for and what suitabilities it can withstand.

THE TANNING PROCESS

There are two main steps completed during a tanning process, the first is the raw tanning and the second is finishing.

TANNING

The tanning process starts when the hides in their raw state are delivered to the tannery.

They invariably arrive salted to preserve them from rotting, much the same as fresh food is transported, which is a short term preservative and covered in much dirt and grime, therefore it requires a very experienced person to make that first selection.

This person is looking for several aspects in the hide, quality of overall condition, size, thickness and a minimum of damage.

After selection, the hides are thoroughly washed then immersed in a chemical bath for a period of time.

This process removes all the hair from the skin and neutralises any traces of salt.

The skin becomes very swollen and gelatinous during this process and prepares it for the fleshing and splitting stage.

Fleshing is when the meat side of the skin is scraped and all traces of fat and tissues are removed.

The edges are trimmed to remove any peripheral damage.

The splitting process is where the hide is cut laterally through the hide to a pre determined thickness and a very accurate machine is employed to cut through the hide to produce on average four sheets or layers of equal thickness.

For designer clothes, shoes and accessories, thinner layers would be used and it has been known for a hide to be split between 12 and 18 times but usually only 3 or 4

It is important for the restorer to recognise these layers in their finished state and understand where they should or shouldn’t be used on upholstered furniture or vehicle interiors.

The first layer is the Nappa or Grain split and retains all of the original graining features.

It is also the toughest because it is the outside of the hide and has obviously been weathered for the duration of the beast’s lifetime.

The fibres of the hide are very closely knitted together and it retains much of its tensile strength.

Nappa hides are always used in the manufacture of high quality goods.

The least processing that needs to be done to Nappa hide the higher its commercial value.

The second and third layers are called ‘The Splits’ and are seen as sheets of featureless leather that have no distinguishing marks whatsoever, it is important to know that the nearer the split is to the flesh side the less strength it will retain, because the internal fibres become more open and elasticised.

These splits are used to produce suede or corrected grain pigmented hides.

The last split is called ‘The Crust’ and because of its poor tensile strength will invariably be manufactured into chamois leathers, aprons and other utility wear; it may also be reproduced into glue and additives to pet foods but as time goes by, new techniques and new rules are put in place and certain older uses are slowly dwindling out.

The hides are now ready for the tanning process.

As of as it used to be there was two main types of commercial tanning, those being vegetable dye tanning and chromium salts tanning.

Vegetable tanning is the longer of the two processes and is invariably restricted to top quality hides.

Chromium tanning is the quicker of the two processes and is recognised as the process that has revolutionised the tanning industry.

The hides are dipped into a bath of chromium salts for a managed period of time and when dried they appear a very light blue in colour known in the industry as wet blue.

The hides are then dipped into an aniline dye bath which will then give it the base colour.

Because the chrome hides after tanning adopt this very pale blue appearance it has made it possible for the tanner to extend his colour ranges into the more lighter pastel shades.

Higher quality leather would be dyed the same colour as the finished outer face.

Chromium tanned hides are also much lighter in weight when finished, compared to vegetable tanned hides and are therefore much more versatile in their uses.

 FINISHING

Having been dyed, the hides are then stretched on frames and rehydrated in humidification chambers then allowed to rest for a period of time.

The better quality hides, ie Nappa are selected for drum dyeing.

This is quite a lengthy process and necessitates the hide being placed into a large revolving wooden drum.

Aniline dyes, conditioning agents and oils are also placed into the drum and the hides are revolved for anything up to 2-3 days.

The end result is that the hide is dyed right through and on completion adopts a very silky lustrous texture.

The hides are also heavier in weight to those that have been chromium processed.

After the resting period, the hides are ready for pigmentation.

The base dye will invariably compliment the final colour and they are divided into categories for processing.

Lesser quality Nappa hides will receive a covering pigment coat.

Some featureless second splits will obviously become Nu buk or Suede.

Other second and third splits will be pigmented and have an artificial grain impressed into them with the use of a heated graining press or roller.

The designer needs to remember these processes to be able to identify the types of leather in the field.

In general it is safe to assume that heavily pigmented leather will probably be covering a lesser quality split.

Remember the tanner’s skill is to make a hide appear better than it is.

Once the hides have been pigmented they are sprayed with several clear lacquer coats, either matt, satin or gloss, and then polished with conditioning oil.

Once dried they are then dispatched to the relevant manufacturer.

IDENTIFICATION OF LEATHER TYPES (example)

In the leather world, there is leather that is numbered with categories according to the list below, however some may differ for example below the higher the category number the higher the quality is expected.

TYPES OF LEATHER

No. 1 – Pure Aniline: cat 30

A top quality Nappa hide. The original outer split which has been aniline drum dyed with no clear lacquer finishing coat applied.

No. 2 – Semi Aniline: cat 25

The same as No. 1 with the addition of a protective clear lacquer coat applied and sometimes a slight pigment colour to enhance the finish, i.e, suavage or antique effect. The leather will also reflect a higher sheen level and usually be transparent in effect.

No. 3 – Pull Up Hide: cat 20

Same as No. 1 drum dyed with additional protective oils added into the process. The hide becomes so totally impregnated with the protective oil and waxes that in theory it will repel any form of contamination but this is not the case once the leather is in use. This leather type now falls into the semi aniline category because it has a protective coat so there fore is not a pure aniline.

No. 4 – Pigment Coated Hide: cat 15 or 20

This is a high quality or substandard top split that requires a pigment coat to enhance the overall appearance.  It will also be finished with a clear protective lacquer. The pigment finish may be of different qualities and type of product, eg. Waterbased, solvent, light cross linkered, heavy cross linkered and by-caste.

No. 5 – Corrected Grain: cat 15 or 20

This is a second or third split that has had a thick pigment coat sprayed onto the surface.  An artificial grain is then impressed into the pigment with the use of a hot graining press or roller.  It will also be finished with a clear protective lacquer coat.

No. 6 – Rub Off Hide: cat 15 or 20

This is leather that has been pigmented, artificially grained and then sprayed again with a darker more translucent pigment or lacquer.  When this hide is used as an upholstery cover, on completion of covering the pieces of furniture, a solvent cloth is rubbed over the body contact area which removes the top darker pigmented layer.  The first colour then shows through which in turn gives the appearance of an antiqued worn effect.

No. 7 – Nu Buk or Suede: cat 30

A middle split that has been sanded flat and aniline dyed only.  Some splits are impressed with an artificial grain and then lightly sanded, this accentuates the grain but still retains the texture of suede.

No. 8 – Cross Linkered Hide: cat 10, 15 or 20

This is a water based pigment coat that is made up of two components.  When mixed together one component reacts with the other and creates an extremely robust finish coat.

No. 9 – By-Caste Finish: cat 10 or 15

This leather is finished in a polyurethane or polyester type coating.

Leather Type Identification

Aniline: Aniline leathers are top quality natural leathers in which the actual surface grain markings of the true leather (hide) are visible.

They have very little or no protective treatments applied. Natural leathers can be classified as Natural, Pure, & Un-Protected and are usually coloured with a transparent leather dye.

A variety of clear finishes such as oil, wax, nitrocellulose and urethane protective coatings, which do not inhibit the softness or breathing of leather, are applied to the surface.

These finishes allow the natural leather markings to show through the finish.

Aniline leathers require different cleaning procedures than protected leather due to its porous nature.

Aniline leather is prone to sun fading.

Identifying characteristics: very easy to scratch; water drops will darken the colour and then dry back to natural colour.

Pigmented/Protected/Top Coated/Painted: This is the most common leather type used in furniture, approximately 90% of the market.

This leather has a uniform appearance and colour.

The leather has an intense colour and a definite pattern (grain).

You cannot see any natural leather markings through the top coatings, because a pigmented leather paint coat is applied to the surface.

It is then sealed with a durable finish.

Properly maintained, this finish will provide years of cleaning ability and durability.

Identifying characteristics: uniform colour and grain patterns; will not scratch easily; water drops will not change colour.

Nubuck: These are natural Aniline leathers that have been surface brushed or buffed on the “grain” side of the leather creating a nap and leaving a texture similar to velvet (softness of all leathers to the touch).

Usually Nubuck has a natural finish, but may have a light protective coat and a transparent leather dye for colour.

This process increases the leather’s surface exposure making it extremely absorbent to body oils and soil, and difficult to clean effectively.

Identifying characteristics: very soft to the touch, will scratch or scuff very easily; water drops will darken the leather but it returns to its original colour after drying.

This page is provided for information to our customers that frequently ask about leather and how do we know whether to use it or not.

Looking for a custom leather interior? Get in touch.

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