Leather for Handcrafting- An Introductory Study by Santosh Kumar Jha
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Leather for Handcrafting- An Introductory Study by Santosh Kumar Jha

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Leather for Handcrafting- An Introductory Study

Leather for Handcrafting- An Introductory Study

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Leather for Handcrafting- An Introductory Study by Santosh Kumar Jha Leather for Handcrafting- An Introductory Study by Santosh Kumar Jha Presentation Transcript

  • 1 Leather For Handcrafting Study By Santosh Kumar Jha PhD (Crafts), PGD(Crafts & Design), MBA(Marketing) FOR HANDCRAFT DESIGN & DEVELOPMENT
  • 2 What is leather? The British Standard Definition of leather is: 'Hide or skin with its original fibrous structure more or less intact, tanned to be imputrescible. The hair or wool may, or may not, have been removed. It is also made from a hide or skin that has been split into layers or segmented either before or after tanning.'BS: 2780. The amount of surface coating applied to the leather influences whether or not the item can be described as genuine leather. '..If the leather has a surface coating, the mean thickness of this surface layer, however applied, has to be 0.15mm or less, and does not exceed 30% of the overall thickness'. BS: 2780. What is not leather? There are many types of leather items sold and described as leather, when in actual fact they are imitations. Some of the more common ones are described below. Bonded Leather Fibre 'Hide or skin with its original fibrous structure more or less intact... If the tanned hide is disintegrated mechanically and/or chemically into fibrous particles, mall pieces or powders and then, with or without a binding agent is
  • 3 made into sheets, such sheets are not leather' BS: 2780 It is possible to see the incorporation of several material types within this bonded leather structure as different colour types. Advantages: • Cheap • Uniform cutting area Disadvantages: • Not leather • Poor flexibility • Not durable • Little strength • Looks cheap Coated Leather 'A product where the finish thickness does not exceed 30% but is in excess of 0.15mm' The darker region toward the grain side of the leather contains the actual coating, which can be constructed with various chemical materials, such as a polyurethane mix. As the finish thickness exceeds 0.15mm, it cannot be termed genuine leather. Advantages: • Cheap • Consistent surface Disadvantages: • Lacks natural look • Not porous • Physical performance, flex etc (low)
  • 4 Laminated Leather The main features of laminated leathers are that they are a composite of two or more layers, where the laminate has been affixed to the flesh side. Also a difference between this leather type and a coated leather is that the laminate accounts for greater than 30% of the leathers overall thickness. Advantages: • Consistent surface • Some flexibility and strength • Colour and light fastness good Disadvantages: • Lacks natural look • Not porous • Physical performance not as good (tends to crack) How much of a product should be leather? You may have bought a pair of leather shoes or a leather wallet, and having looked at it closely wondered just how much of it is leather and how it can be sold as a 'genuine leather' article. Manufacturers of leather articles are allowed to construct a product that is traded as 'genuine leather' with non-leather materials provided the incorporation on non- leather materials does not exceed specific levels.
  • 5 The EC Directive 94/11 on Footwear Labelling states that a genuine leather shoe must contain the following proportions of leather: • Upper - 80% of surface area • Lining/Sock - 80% of surface area • Sole - 80% of volume 'If no one material accounts for at least 80%, information should be given on the two main materials used in the composition of the footwear.' Guidelines The following are general guidelines regarding the composition of leather articles: Watch Straps/Belts Where both the outer layer and lining are leather, then it can be described as leather, genuine leather, or real leather provided no other materials comprise more than 50% of the surface area. However, if a strap or belt meets the previous definition of leather but at the same time clearly comprises less than 50% leather in total volume, then it should not be described as leather without further qualification as this may be misleading. Upholstery There are essentially two zones: "contact areas" i.e. seats, arm rests, vertical seat backs and rolls, and "non-contact areas" e.g. outside arms and back. Furniture should only be described
  • 6 as "leather" if both the "contact" and "non-contact" areas are leather. Where only the "contact areas" are leather then the furniture should not be described as "leather" unless the description "leather chair with non leather areas" is used. Sometimes the term "leather faced" is used under these circumstances. Luggage, Bags, Leathergoods At least 80% of the surface area of the main body should be leather (excluding internal dividers, pockets, pen holders etc.) More Information Leather Descriptions and Definitions (1.2MB PDF) - Includes definitions of different types of leather. British Standards Faking it There are alternatives that don't attempt to imitate leather and there are substitutes which are designed to imitate leather. These substitutes are legal if sold as such, but become fakes when they are passed off as leather. Another product sometimes falsely described as leather is made by compacting leather fibres with a binding agent to hold them together. Because the fibres are stuck together rather than interwoven the product
  • 7 lacks the flexibility and durability of real leather. Legally this material must be described as 'bonded leather fibre'. If you are concerned about a leather item that you feel is not ‘leather', or for other assistance with consumer protection issues in the UK contact your local Trading Standards office which you can find via the Trading Standards Website. Areas You'd be surprised the first time you see a full hide. Not only are they much larger than you think, they vary much more than you'd expect too. Leather from different parts of the animal varies in its characteristics, and this has to be taken into account when using leather in products. The hide thickness varies all over the animal, and to get it to the right thickness it is usually split on a special cutting machine or buffed to an even thickness. The main parts of the hide are shown in the diagram below Shoulder - the shoulder is thick and strong but tends to crease easily as this part of the hide is affected by movements of the head Butt - the fibres in this part of the hide are tightly packed and hence the strongest part of the hide Belly - this part of the hide is quite thin and has a much looser fibre structure than the back, and often stretches under stress. Axillae - these are like the human armpits - they move a lot - so the fibre
  • 8 structure is quite loose, making it even more prone to loosening than the belly areas. From Hide to Hair Different parts of a hide have different properties in terms of strength, flexibility and durability. This makes some parts of a hide more suitable for use in sofa manufacturing than others. Science For a material that is so versatile, stylish and practical you could be fooled into thinking it is an extremely complicated material...far from it! There are basically just three main materials from which hides and skins are made :- • Water 60-65% • Protein 25-30% • Fats 5-10% The protein is mainly collagen (found in many cosmetics) and it is this collagen that is transformed into leather by the tanning process. In good shape Raw hides and skins have four main parts - an epidermis, grain, corium and flesh - as shown in the diagram below :- Two of these layers - the epidermis (which is a thin protective layer of cells during the life of an animal) and fleshy remains - are removed during tanning by a process called liming. This
  • 9 leaves just the grain and the corium, the interesting parts! The grain layer is made of collagen and elastin protein fibres (found in many moisturisers and facial creams), and its structure varies quite a bit depending on the age, breed and lifestyle of the animal. The grain carries many distinctive marks such as insect bites, growth marks and wound scars giving the leather a unique appearance. The corium is packed with collagen protein fibres, arranged in larger bundles and interwoven to give the structure great strength, excellent elasticity and durability. The thickness of the corium increases with age which is why calfskins are thinner, smoother and softer than the hides of mature animals. Hides from cows are smoother, thinner and softer than the hides of mature male bull hides which are thick, tough, course grained and very strong. Thick hides are often too thick for their end use and so they sometimes have to be split layerwise through the corium to give what we call a ‘grain split' - used for grain leather - and a ‘flesh split', used mainly for suede leather. Another little trick is to apply an artificial grain layer to the flesh split to make it look like grain leather! However the strength of these so called ‘finished split' leathers is reduced since the corium lacks the strength of the corium found in the grain layer.
  • 10 ThanksTo primary information source: Web Source: http://www.all-about-leather.co.uk About Study Source