Sunday, December 5, 2010
Shoes: Why kangaroo leather?
From 1790 convict shoemakers made large quantities of footwear. Inferior bovine hides meant alternative were sought and from 1805, Kangaroo leather was used as a cheap and convenient substitute for kid leather. It transpired kangaroo skin had superior qualities of high strength, light weight and durability which made it ideal for finer boots, whips, gloves and eventually sporting shoes. By the mid nineteenth century there were many small tanneries established as the demand for quality kangaroo products rose across the word. As today an estimated 80% of kangaroo skin products went abroad. The native marsupial developed a special skin which it to survive harshest environments and against many predators. Studies conducted by the Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO) confirmed kangaroo was one of the strongest leathers of similar substance. When split into thinner substances kangaroo retains much of its original tensile strength i.e. when split to 20% of original thickness kangaroo retains between 30 to 60% of the tensile strength of the unsplit hide. As a hide it is lighter and stronger than the hide of a cow (bovine) or goat. It has 10 times the tensile strength of cowhide and is 50% stronger than goatskin. Microscopically kangaroo presents with uniform orientation of collagen fibre bundles in parallel with the skin surface. By comparison cattle has complex weaving patterns with fibre bundles angled as much as 90 degrees to the skin surface. In kangaroo skin the low angle of weave running parallel to the surface of the skin acts like a rope gives the material exceptional strength. Because there is no fat within kangaroo hide the tanning process does not leave “voids” which can cause a reduction in strength per unit thickness. The hide also does not contain sweat glands or erector pili muscles and elastin is evenly distributed throughout the skin thickness. This structural uniformity explains both the high tensile strength of the whole leather and the greater retention of strength in splits. By comparison bovine skin is much more complex in cross section. Hence it has many more weak points from which tears can start when placed under tension. In addition when sliced into splits the collagen fibres running at significant angles to the skin surface are cut which further weakens structural strength. In Australia, kangaroos have never been farmed and hides are produced from free ranging wild animals. Today most species of macropods are protected from hunting by law. Most of the leather used today is a by-product of beef industry. Fifty (50) % is used to produce shoes, 25% to make clothing, 15% for upholstery and the rest is used to produce accessories.