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Leather For Handcrafting
Study By
Santosh Kumar Jha PhD (Crafts), PGD(Crafts & Design), MBA(Marketing)
FOR HANDCRAFT
DESIGN &
DEVELOPMENT
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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
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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)
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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.
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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
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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
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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
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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
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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.
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Thanks To primary information source:
Web Source: http://www.all-about-leather.co.uk
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