Survival

The hides and skins of animals were one of nature's first by-products which man learned to use for survival and comfort. In the living animal 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 covering for tents and tepees. Indeed such is the versatility of animal skin that one can look through many key stages of the development of civilisation and identify how leather has helped to nudge our society along to the endearing stage that we have reached today.

In shipping some of the first boats, coracles, were made of hides. The first carrying vessels for wine and water 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, particularly the open topped motor car, leather was the preferred material until man's love affair with the automobile lead us to realise that there was not enough leather available in the world to satisfy mankind's appetite.

Most important is the footwear sector. For all the time that mankind has worn shoes leather has been the key material in foot protection.

Perhaps less well recognised, but equally vital, the bagpipes rely on a leather bag inside for its stirring tones, grace and power that strikes fear into enemies in battle.

We need to note 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 tanner's job is rather to collect hides and skins that become available from normal farming practice and to prevent them becoming an environmental hazard wasting away in the corners.

There are alternate uses for hides and skins - an additive in foodstuffs, an assist in cosmetics, a covering for sausages, the preparation of gelatine - but these are all small uses in terms of volume. If the tanning industry were not interested in the hides and skins of the world there would be a dramatic reduction in skin collection and while some skins would be left on the animal to be eaten with the meat the majority of the hides and skins of the world would be found putrefying in spoil heaps at the back of abattoirs 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 value of the raw hides and skins - while low in the series of benefits which the community gain from an animal in its lifetime - constitutes a major income for otherwise very poor communities.

At the current moment about 18 billion square feet of leather are produced per year throughout the world, about 65% of this coming from cattle, followed in volume terms by sheep then goat skins. Other animal skins can be used but their quantities are very small. Pigs and deer should not be ignored, however.

Demand for leather over the centuries has risen with the world's population, and as that population has become more prosperous. The leather industry, being unable to expand its raw material base, has responded by conceding end uses. The invention of glass, paper, the introduction 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 it 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.

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 end use.

The tanners job comes down to cleaning out the fibres, ordering the network geometrically (adjusting the weave), order the fibres morphologically (the fineness of the separation of the fibres) and chemically stabilise what has been created.

Because the leather industry is small and scattered throughout the world, the industry tended to remain a localised craft technology until the last hundred years. The leather industry missed the industrial revolution and has transformed itself from an art to a science - where artistry still remains important - in these last hundred years. Even now, there is much which is not well understood in scientific terms about the leather making process.

There are many ways of conserving hides and skins to make them usable and some of these are permanent and some temporary. Methods of leather making used by man developed as you would expect in accordance with what materials he had available locally. The prime tanning material used until the beginning of this century was tannin extracted from vegetable material. Each locality searched for the plants or trees, or parts of those plants and trees, which contained the highest concentration of tannin and would be most effective in use. Thus in England tanners have historically made great use of oak bark, in the USA hemlock, and in many parts of Russia the birch bark was most used.

In addition to vegetable tanning other methods were employed. The tepees of the North American Indian used raw hides which became effectively preserved through the action of smoke from the fires they lit inside the tent.

Eskimos make great use of hides and skins for their kayaks and clothing, and sit up at night chewing the hides.The action of the enzymes in the saliva gives a level of both preservation and tanning. As time past other tanning materials were found such as potash alum - used to make lovely white doe skin gloves which were so famous ion the 18th and 19th centuries. Alum tanning (tawing) was the foundation of the leather that is used to make cricket balls. In ancient times alum was a much sought after material and the Vatican's search for and attempts to monopolise supply is a famous part of fifteenth century history. Alum is, of course, also used as a mordant in the dyeing of textiles.

Other chemicals were used. Fish oils, especially cod, for the manufacture of chamois wash leathers.

Today over ninety per cent of all the world's leather is tanned with chromium salts developed at the end of last century. This development was carried out in the USA, primarily in tanneries in Philadelphia and Gloversville. One of the first European tanneries to adopt this technology was Pavlova in Abingdon, England. Some concern has arisen over the environmental suitability of chrome tanning. Most of the fears are incorrect, if both the process and the handling of wastes is done correctly. With a hundred years of experience, chrome tanning and its problems are understood quite well. Rushing to aluminium and other things less well researched would be an error. The argument that vegetable tanning is more natural as it uses only vegetable material does not stand up. Vegetable tanning is inefficient and uses high quantities of materials. This creates a big effluent problem - particularly BOD - and a major problem in finding enough vegetable tanning material for the job. Vegetable tanning has a history of many centuries of creating problems damaging forests and swamp trees.

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 leather for shoes, for oil seals for a mechanical digger, or for brake blocks for a pedal cycle. Equally they can take an African hairsheep and manufacture leather less than 0.5 mm thick for the finest gloves.

In its standard forms, leather offers a tremendous range of properties. Good abrasion to resistance, which is why it is used in sole leather and motorcycle wear. Unlike some synthetic materials tested for motorcycles it does not melt in the heat generated when a cyclist slides over the ground. It offers warmth and insulation. The strength of leather is exemplified in its role in harness and belting safety equipment. It is wind resistant, having non-aligned pores. It has an ability to absorb sweat and to transmit it through its structure to the surface. This means that in uses such as gloves and footwear the surface of the skin can remain dry and warm. Its ability to adjust to the shape of the foot is an important factor since our two feet are never the same size.

Because leather is in a way an international commodity its manufacture has moved for economic reasons - the availability of raw material supplies and the accessibility of low cost labour - into the third world. The movement of the footwear, clothing, glove and tanning business has been a major macro economic feature of the last fifty years or more.

This has forced the technology forward as developed world tanners have looked to technology to give them added value to stay in business.

With such a strong and versatile material this has proven very fertile ground. I would confidently say that this book is not yet fully opened, but tanners have yet to prove to us that they are willing to escape the mental frame of past years and look at their product from a really creative standpoint. We have smart materials in all other sectors, but not yet in leather. So the technology can still be considered under exploited.

Over the last twenty years most progress has been made in water resistance, towards levels that can be called, in given circumstances waterproof. There are many ways of making leather hydrophobic. These include stuffing greases, hydrophobic oils, fluorocarbons, silicone treatments, chrome stearate compounds, dicarboxylic acid chains, and selected acrylic resins. The skills in this processing are to avoid loss of comfort, to make the property lasting, and to allow the leather to remain soft when it dries after a major wetting.

When handling sweat the mechanisms are exceedingly complex. Leather itself manages sweat well enough from a comfort aspect, the problem is that most tannages are gradually broken down by sweat and the leather becomes hard and gelatinous. Aldehyde tannages are one of the main methods used to counteract sweat, being less likely to be broken down.

Some tanners have thought that leather was in competition with synthetics, and there was considerable panic in this regard in the late sixties and seventies. Of course there is a level of competition, which will be eventually decided on a balance of performance and price. No one can be complacent, but the two product areas should be able to find a natural balance. Leather has a natural feel that is loved by athletes and most consumers.

One major aspect of leather is the cocktail of performance that it offers. If you need absolute fireproofness Nomex is better than leather, but racing drivers will still add varying amounts of leather to the finger and palms to ensure the best manual dexterity. Gloves made in sweat resistant leather are preferred for fast jet pilots. In footwear comfort and fit are still dependent on leather although in some extreme conditions - snow for example - alternate materials are valid.

Membranes have a role in footwear, but it seems likely that their use will diminish as leather improves and seam sealing gets better. Again though, membranes appear likely to improve, and as they always have done, they work better with a good performance leather rather than a poor one which wicks water over the top inside the shoe.

It is only recently that the industry has realised what a technically valuable material they are working with, and that we are really only at the beginning of a new era in the search of true high performance and smart products.

Leather can be considered useful in quite unexpected ways. In ancient Persia 3000 years ago the power of 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 re-upholstered in leather made from his father's skin.

Can there be a better example of leather raising mankind's performance?

Adapted from a lecture given to the "Survival - 90" Conference at the University of Leeds, March 1990