The hides and skins of animals were one of the first of nature’s by-products which man learned how to use to make life bearable on this wonderful earth of ours.
In life skin serves to protect and to cover, it provides warmth, it is waterproof and its ability to breathe is required to stay alive. In our earliest society its versatility, strength and other properties were discovered first in clothing, then as a binding for tools and weapons, and as a covering material for tents and teepees. Indeed such is the versatility of an animal skin that one can identify how leather has played a major role in many key stages of the development of civilisation.
In shipping some of the first boats, coracles, were made of hides. The first carrying vessels for water and wine came from hides and skins. Leather provided the first material for writing in the form of parchment and vellum. The first wheels invented by man had, in many instances, leather binding the rims. In general clothing leather has always been important in different forms providing warmth or protection. In upholstery until the last two centuries it was the prime material to be used and on the invention of the motor car leather was the preferred material until we recognised that there was not enough leather available in the world to satisfy the huge growth in automobiles that was taking place. Most important of course is the footwear sector. For all the time that mankind has worn shoes leather has been the key material in foot protection.
We need to recognise that the manufacture of leather is strictly a by-product activity. Hides and skins are a renewable resource but they are never renewed as a consequence of demand for finished leather. The value which society puts on leather is very great, but it is not adequate to persuade farmers to keep animals only for that purpose. The tanners’ job is rather to collect hides and skins that become available from normal farm practice and to prevent them becoming an environmental hazard wasting away in the corners. There are alternate uses for leather – an additive in foodstuff, in certain instances an assist in cosmetics, a covering for sausages or the preparation of gelatine, but they are small uses and if the tanning industry were not interested in the hides and skins of the world, there would be a dramatic reduction in collection. The majority of the hides and skins of the world would putrefy in spoil heats at the back of abattoirs or in native villages.
The leather industry is also of economic interest from the point of view that its raw material is widely spread throughout the world and in certain areas of the world – the Indian Sub Continent and large parts of Africa – the value of the skins, albeit low in the series of benefits which the community gain from an animal in its lifetime, do constitute a very meaningful income for otherwise very poor communities.
At the current moment about 18 billion sq.ft. of leather are produced per year throughout the world. About 65% of this comes from cattle hide followed in volume terms by sheep and then goat skins. Other animal skins can be used but their quantities are very small. The simple fact remains that the leather industry will shrink or expand to the available supply of raw material.Current research indicates that by the end of the century demand for leather worldwide will be in the order of 21 billion sq.ft. while the best estimates of supply struggle to reach 20 billion sq.ft.
Demand for leather over the centuries has of course risen as the world’s population has increased and become more prosperous. The leather industry not being able to expand its raw material base, has responded by conceding end uses. The invention of glass, paper, the greater utilisation of timber in construction and boat-building, of metal in armour and weapons, permitted this adjustment to take place gradually. As one looks at the major uses of leather today, the prime areas where leather has remained are those where its performance benefits are most noticeable. There is an overlap where the natural richness and the beauty of the material retains its use and there is an overlap into fashion, but essentially leather retains those segments of its traditional marketplace where its performance characteristics, its protection, its health giving features and its sheer comfort, are best utilised. With a shortage of five to ten per cent in the supply looming over the next decade we can expect these trends to quicken. With continued improvement in the synthetics being developed to help fill this gap the tanner dare not relax. The market will expect good looking, fashionable leathers with outstanding technical features built in. We are in the era of customised leather, with technical qualities tailored to meet specific end user requirements.
The story of leather is the story of nature’s non woven material. Leather is an intricate protein based, three dimensional fibre network built up out of amino acid building blocks. All of its essential required properties have been put in place by God and Nature and the tanners job is to condition this base material into something which first will be resistant to bacterial putrefaction and secondly to adjust its properties in accordance with each individual required end-use.
There are many ways of conserving hides and skins to make them usable and some of these are temporary and some permanent. Because the leather industry is widely scattered throughout the world it has tended to remain very much a localised craft industry. The transition from an art to a science has in large part been made in the last one hundred years and there is still much about the leather making process which is not fully explained in scientific terms.
Methods of leather making used by man developed as you would expect in accordance with what materials he had available locally. As we know the tanning material used until the beginning of this century was tannin extracted from vegetable material with a search being made in each locality for the right plants or trees, or part of those plants and trees, which contained the highest concentration of tannin and would be most effective in use. Thus in England tanners historically have made great use of oak bark, in the United States the hemlock and in certain parts of Russia it is the birch bark which was used as the tanning material. In addition to that other methods were used, the teepees of the American Indian use raw hides which effectively became preserved through the action of the smoke from the fires which they lit inside their tents. Eskimos make great use of hides and skins for their kayaks and clothing and sat up at night chewing the hides so that the action of enzymes would give a level of preservation and tanning.
As time past other tanning materials were found such as potash alum which was used to make the lovely white doe skin gloves which were so famous in the 18th and 19th century and potash alum became the tannage which was the foundation of the leather that’s used for the manufacture of cricket balls. Other chemical materials were used such as fish oils particularly cod oil which is used in the manufacture of chamois leather. It is fascinating to note that the Industrial Revolution rather left the leather industry untouched, and it was last century when the real breakthrough came in manufacturing technology and practise. As well as the introduction of new types of machinery and a high degree of mechanisation the late 1800’s gave us chrome tanning. The use of chromium salts allowed us to achieve a high level of crosslinking within the fibre structure, and with it better resistance to high temperatures.
Now well over ninety per cent of the world’s leather is made using chromium salts. So we entered the 20th century with quite a strong and expanding chemical base for consideration when developing new leathers or adjusting old ones. This is important, since with recognition that our industry has real environmental responsibilities we have a responsibility to continuously strive to improve and find a better way to make our product. Tanners have to consider the quality and quantity of effluent produced, the amounts of water and chemical inputs they use, and the impact that tanning makes on the atmosphere and the ozone layer. Not only does the customised economy expect technically advanced leathers, it also expects environmental consideration. This is an area that requires careful analysis, since it often takes many years to really understand the full implications of using a particular process. It is also important to track the environmental impact from cradle to grave, and not merely to take a judgmental position on the basis of a narrow snapshot.
The achievement of fitness for purpose in leather comes from choosing the right type of raw material and picking the appropriate process. Tanners are capable of taking certain types of cattle hide and making them suited for sole leathers, for oil seals for a mechanical digger or for brake blocks for a pedal cycle. Equally they can take a fine African hairsheep and manufacture leather under ½mm thick with great strength to be made into gloves which protect the hands while maintaining, indeed sometimes improving, manual dexterity.
In its standard forms, leather offers a tremendous range of properties. Good abrasion resistance which is why it has been used so much in sole leather and certain skins and tannages form a major part of motorcycle wear. It offers warmth and insulation; according to the Leather Research organisation in the United Kingdom each cubic centimetre of leather is as an effective insulator as asbestos. The strength which is apparent but exemplified in the role it has to play in harnesses and belting and safety equipment. Water resistance: a natural ability to repel water in its most normal states. An ability to absorb sweat and transmit it through to the surface so that in confined uses such as footwear and gloves, the surface of the skin remains dry and warm at all times giving maximum health benefits. Also in footwear, an ability to adjust to the shape of the foot – an important factor since our two feet are never exactly the same – so that after the first wear unless you have purchased a particularly bad pair of shoes for the sake of economy or fashion, your feet should be comfortable and healthy.
Because leather is in a way an international commodity and has moved for economic reasons -the availability of raw material supplies and the accessibility of cheap labour – into the Third World, my company, which has wished to retain its tanning presence in the developed world, has been looking since the early ninety fifties at how it can add value to leather to make sense of the higher costs of manufacture which we have to live with. The early part of this period was dedicated towards improving standard practices making regular leather last longer, hold its colour faster and for certain end-uses, to be washable first by hand and then by machine. For the last 20 years we have been looking in greater detail at what can be done to enhance the performance characteristics of leather to make it more perfectly suited for the higher demands which modern lifestyle requires of it.
We are fortunate that we start with such a strong versatile core material and our technicians have been involved in elegantly adjusting and manipulating the surface chemistry while doing the minimum to affect the natural qualities of the core.
One of our greatest difficulties in this activity is finding meaningful test methods. While there are many useful leather tests, both to validate the quality of processing and to allow the comparison of one piece of leather with the next we have in many instances come upon real difficulties in finding tests which correlate to the modern demands made on leather in wear and in use. This is particularly true in relation to areas such as fastness of colour in a variety of conditions. Not only do we want to be sure our leathers will meet expectations in use but we also want to be able to put our new generation of leathers in a meaningful context alongside the performance synthetic materials, textile materials , linings and membranes with which we also have to live and occasionally compete. We recognise that the post recessional consumer has expectations of meaningful value for money and being in the main better educated than previous generations is far more prepared and able to complain. The consumer that we are dealing with now has expectations of enhanced levels of performance as a given. The leather that all our tanneries are offering to consumers is a wonderful material but it is our responsibility to continuously improve that material and produce it so in a consistent and guaranteeable way.
One of the major areas where leather has improved has been in resistance to water. The industry has now moved passed water resiatance alone to nearly acceptable levels of waterproofness. The skill now lies in doing this without compromising the comfort aspects of the leather. There are many methods of improving the waterproofness of leather including using stuffing greases, hydrophobic oils, fluorocarbon, silicone treatments, chrome stearate compounds and dicarboxylic acid chains. The search has been for systems which will be through the thickness of the leather, substantive to the leather and so not easily worn away or washed away. We have adjusted our leather so that should it become wet its water uptake will be exceedingly low and its recovery time exceedingly rapid. It should recover to its original, natural level of softness.
When handling sweat the mechanisms are exceedingly complicated. We recognise that leather has been particularly good in this respect but our concern has more been to preserve the leather itself against sweat rather than to improve an already satisfactory mechanism. The technique is to find a way of preventing the chemicals in sweat from detanning the leather and eventually gelatinising it.
Another area of great importance is density. One of the major difficulties of leather when worn as clothing is its weight. In the seventies the leather industry successfully produced bovine that was thin, soft and much better suited to clothing than previous generations. Shortly after fine work by Spanish tanners reduced the skins of the thick and difficult woolly domestic sheepskin down to 0.5mm while still being strong enough to be crafted into quality garments. Despite these improvements reducing the weight per square foot still remains a challenge for the tanners of the world, particularly since this must be achieved without detracting from the other performance characteristics of the leather.
As I said earlier leather is not in competition with alternate performance materials, but rather view leather as another weapon in the armoury for use in the sports and performance field. If you want absolute fireproofness Nomex is better than leather. Racing drivers will still add varying quantities of leather to the fingers and palms of their gloves to maintain manual dexterity. In flight situations where manual dexterity is even more important, gloves made in sweat resistant leather are preferred for fast jet flying on the basis that the fire resistance is adequate and manual dexterity and other properties are much more important. In footwear comfort and fit are still dependent on leather although in some extreme conditions it is quite valid to use additional materials such as the new membranes to improve the performance particularly in wet conditions. Initially when these membranes came onto the marketplace there was a suspicion that they would displace our material. Certainly for a while when they were used with leather, it was felt that cheap, simple leathers would be adequate. It is now recognised that if an expensive performance item such as a membrane is going to be used it requires a performance leather to get the best out of it. The leather working with a membrane in footwear is required to be low wicking and is much improved if it has low water uptake since it then helps the pressure gradient which sends sweat through the vast majority of membrane types.
Leather’s ability to hold in excess of 25% humidity, means that a performance lining material helps the membrane handle sweat while retaining maximum foot comfort.This highlights an area upon which tanners developing technical leathers for the nineties must build. In our own leathers where we have carefully adapted products for individual markets we call it balanced thermal insulation. This effectively describes the high levels of comfort afforded to the body in both hot and cold conditions, offering good thermal insulation in the cold with wind resistance afforded from the pores being non-aligned, and in warm conditions handling the moisture from sweat in a way which keeps the body cool.
When taking into consideration the various elements which I have just discussed in detail you can recognise that we have been able to develop not only a range of products but a process. I would suggest that by following the process of engineering, of customising, our Pittards WR100 we have not only established a product range but a process, and as such a process which gives some pointers as to how the leather can maximise advantage from the inevitable shortage of raw material we will soon be facing.
In considering this fact we need also to recognise that we have major over capacity in the tanning world wide. This has been an uncomfortable fact for over three decades, and it seems certain that as new areas develop and build increasing capacity faster than the old ones close down we will have at least another two decades of too many tanners chasing too few hides and skins. In such an environment the route to survival will be to make the most of our valuable raw material, and in doing so to maximise the technical and performance attributes which are inherent within it.
Thus we do believe that leather remains natures high performance, breathable material and that however fast and successfully alternate materials are produced, well made technically advanced leather will always have a key role to play in man’s performance activities.
Leather can be considered useful in quite unexpected ways. In ancient Persia 3,000 years ago the power of the judges was passed from Father to Son. An instance arose when a judge took a series of bad decisions and it was considered appropriate to remove him from authority. In due course his son found himself sitting on the throne of justice and to remind him of the importance of taking good decisions, he was advised that the throne had been reupholstered in leather made from his father’s skin.
Can there be a better example of leather raising mankind’s performance!
from a lecture given in Shanghai, 6th October 1993