leather identification study by santosh kumar jha

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LEATHER IDENTIFICATION

Study By Santosh Kumar Jha

PhD (Crafts), PGD(Crafts & Design), MBA(Marketing)

This is a crucial part to insuring that the

leather repair products will work

in the most effective possible way. Learn about following Leather

Identification process and the

identification- characteristics to

select leather types for Handcrafting.

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What we need to know about upholstery leathers is that almost all commercially produced comes from the bovine family (bulls, cows & steers) and also from the Asian water buffalo (seldom is buffalo refers to the North American Bison). Hides (from bigger animal) are normally used for upholstery and skins (from smaller animal - pig, sheep or goat) are mainly for garments. So, in upholstery cleaning or restoration it makes no difference which animal or gender they are made from. Rather it is the type of tannage that has significant bearing to the effect of cleaning and conditioning. Vegetable-Tanned leathers appear to be on the brown shade naturally, while Chrome-Tanned leathers are grayish green in color naturally. What if they are aniline dyed through into another color, then

An Overview

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the tell tale sign is that all chrome tanned leathers are softer to the “hand” usually not thicker than 2½ mm. While on a Vegetable-Tanned leather double layers stitching it can average up to 8mm in thickness. A good example is take a look at our precious leather shoe, the soles of the shoe is Vegetable-Tanned leather while the shoe upper is normally Chrome-Tanned. Vegetable-Tanned leathers are more alkaline sensitive, and more fatliquor dependant than Chrome-Tanned leathers. See how the soles of the shoe crack up even though they are frequently wet. So the notion that water alone is sufficient to soften the leather as a conditioner is not true.

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The leather protein fibers has to be pH conditioned below the iso-electric point (pH 3-5) to a cationic (+) charge before an anionic (-) pH 5.0 fatliquor can have an effective long lasting hydrogen bonding effect. Alkalinity above pH 6 will progressively break the chemistry constituent hydrogen bonding and cause the slow denaturing of the leather. Leather upholstery can be divided into the smooth type often refers to as leather. And the velvety type like nubuck (top grain - fine nap) and suede (split suede - coarse nap) refers to as suede. Suede has naps that need to be groom for softness with a “finger writing effect”. Next we need to know that smooth leathers regardless of fashion effects can either by absorbent, semi-absorbent or non-

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absorbent. Leather absorbency also tells us how deep the stain has gone into the structure. Leather identification can be by sight, feel or scratch. From my experience, knowledge by sight alone is the most valuable asset acquired by a professional especially in today pictures by emails. In next pages, we are discussing about various common leather finish types:

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Bovine or “Hair-on Hide” popularly found as a combination with Aniline or Nubuck country style upholstery. Cleaning and rinsing products recommended: Wool Cleaner-5.5 with Wool Rinse4.0. Tools recommended either nubuck Brush-2 or suede Brush-3. Non-stick protection recommended: leather Scent-S.

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“Wet Blue Grain” is what is left on worn-out chrome tanned pigmented leather.

Or

When a solvent spotter or cleaner is been used that accidently removed the pigment finish.

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“Wet Blue Suede” in most cases is further custom dyed for upholstery. Tools recommended: suede Brush-3 & nubuck Eraser-5. Non-stick protection: leather Scent-W.

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“Nubuck” is a result of buffing an aniline leather grain side to produce a fine velvety texture. Tools recommended: Nubuck Brush-2 & Nubuck Eraser-5. Non-stick protection: leather Scent-S.

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“Pure-Aniline” is full grain leather that is fully dyed through with aniline dyes to enhance its inherent beauty. They are the most absorbent among all the smooth leathers that stains easily. Scuff and surface scratch can be easily rectified with Wax Effect-8.6 without need of a color touch-up. Non-stick protection recommended: leather Scent-S. Water spotting (a pH phenomenon) can be easily rectified with leather Rinse’3.0.

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“Aniline” is pure aniline that has a “dye-on” surface dye and a protective top coat.

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“Wax & Oil Pull-Up” is aniline leathers that are infused with both Oil Effect-2.8 and Wax Effect-8.6 to create a pull-up effect.

This wax & oil combination gives the leather a satin look. When the leather is pulled or stretch it becomes lighter in those areas. Therefore seating cushions looses it colors fastest & evidently light marks from scratch are apparent. Softening & strengthening leather with Fatliquor-5.0 prior to reviving the effect with Oil Effect-2.8 & Wax effect-8.6. Non-stick Protection recommended: either leather Scent-B or leather Scent-D.

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“Oil Pull-Up” is aniline leathers that are infused with Oil Effect-2.8 to create a pull-up effect that has a glossy look. Stretching reveals a lighter color. Fatliquor-5.0 is applied for softening and strengthening prior to Oil Effect-2.8 to revive the pull-up effect.

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“Wax Pull-Up” is aniline leathers that are infused with Wax Effect-8.6 to create a pull-up effect that has a satin look. Fatliquor-5.0 is applied for softening and strengthening prior to Wax Effect-8.6 to revive the pull-up effect. Testing: A stretch reveals a lighter color and heating up with heat blower darken it.

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“Embossed Wax Pull-Up” is similar to the above wax pull-up effect

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“Semi-Aniline” is the best between the aniline and the pigmented in terms of breath-ability & clean-ability. They are usually full grain leathers that have been dyed and lightly micro-pigmented with a fine top finish that is semi-absorbent. Non-stick protection: leather Scent-B

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“Pigmented - Kela Effect” or a cloudy two tone effect with opaque pigment and a top coat finish makes this leather non-absorbent. Non-stick protection recommended: leather Scent-B.

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“Pigmented - Corrected Grain with embossing” this is a low-end non-absorbent leather among the top grain leathers. Non-stick protection recommended: leather Scent-B. The black you see are caused by a black dye transfer, which can be removed by Ink Remover-7.7 without any color touchup.

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“Pigmented - Wiped Effect” has a primary opaque pigment (maroon) and a secondary transparent dye (black) on top of the pigment to create the wiped look with matching topcoat. Non-stick protection recommended: leather-Scent-B.

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“Pigmented - High Gloss” This fashion is common for traditional or office upholstery with an ultra high gloss finish. Non-stick protection recommended: leather-Scent-B.

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“Pigmented - Metallic Effect” Usually done with a secondary effect on top of primary opaque pigment base. Non-stick protection recommended: leather Scent-B

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“Semi-Aniline - Pebble Grain” It is a semi-aniline finish with natural high pebble grain texture. Non-stick protection recommended: leather Scent-B.

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“Vegetable Tanned” leathers are constructed differently with its characteristic thickness sewn without the normal cushion fillings. Non-stick protection recommended: leather Scent-D.

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“Bicast” leathers or synthetic lamination over split leathers are non-absorbent but do scratch quite easily. Wax Effect-8.6 and Leather Scent-D recommended rectifying scuffs depending on the severity.

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Thanks To primary information source:

An article by Mr. R. Koh

Web Source: http://www.leathercleaningrestorationforum.com

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