Leather Industry • sources:US, Argentina, Australia, Brail & Canada Bark-tanned pigskin – for bags & cases,
History 5. Calfskin – used for expensive shoes, handbags and Mechanical Manufacturing Process
• Leather is known to be “the most historic of
similar articles; finer grained & lighter in weight
than cattle hides
strength Fairly good Very good
Vachette leather – for furniture, Terms:
useful materials” motorcars…
• The original primitive method was simply
• sources: US & Europe o Tanning – the skin is turned into leather
drying, either in air & in sunlight.
6. Kidskin – imported from countries where goats Japanese leather – similar to alum-tanned
o Tannins – complex mixtures of glucosides
are raised for milk & meat leather, for braces.
• In 1200 B.C., (age of the Homeric heroes) Greeks • sources: India, SA, & Central Africa 3. Fine leather – for gloves, lining, and of various polyphenols, combining
were using leather garments and later spread 7. Horse hides – used for shoes, jackets & sports bookbinding between the collagen fibers of the skin.
Characteristics of Leather: liberates sugar during the tanning
throughout the Roman Empire (The protective equipment
armor of the Roman soldier was a heavy leather • sources: France & Belgium
Fancy leather – for handbags & other process
o Uneven chemical composition articles, made from crocodiles, snakes, SKIN + TANNIN = LEATHER + SUGAR
shirt.). 8. Pigskin – sources: US, Central Europe & South
o Tensile strength – determines to what degree lizards… • acidity of pH is controlled by the used
o By trial and error, man discovered methods of
9. Lizards & Snakes Skin – provide leather with
the leather may subjected to stretching.
Glove leather – includes alum salt leather, of sulfuric acid.
preserving and softening leather treating animal o Permeability – determines to what extent the
skins with smoke, grease and bark extracts.
unusual textures and colors for shoes, handbags, &
leather of a shoe garment will allow the
nappa leather, & chamois leather o Keratin – a protein containing crystine
luggage 4. Technical leather – for hose, straps, drums & residue which is easily attacked by an
o Hebrews originated the tanning effects of removal of water of perspiration from the
10. Deerskin & Buckskin – skins from the deer parchments. alkali.
leaves/ barks of certain trees in water. 11. Water Buffalo, ostriches, seals, & sharks – for Belting leather
o Changeability of area – determines the o Neutralization – adjustment of pH for
• In the middle ages, “England” – center for degree of physical discomfort in a shoe Hose leather - for pumps different types of skin
leather making & for the export of leather. resulting from the variability of relative Lace leather
o Chinese knew the art of making leather.
Layers of Animal Skin
humidity. Strap leather
o Liming – loosening & removing the
Temper – measured by folding lightly in Machine leather epidermis & hair from the hide
o “Buckskin tan” – type of leather made by the
Epidermis – outer layer constituting 1% of upper leather Gas mask leather 10% lime, 2% Na2S (based on hide
the total skin & chiefly consists of protein
developed great skills in leather work keratin.
o Leather resilience – for soles and heels Parchment & drum leather – made from weight)
o Susceptibility to acid pigskin, calfskin, goat skin & sheep skin. 3 – 7 days/vats
before the coming of the white man.
knew nothing of the bark tanning methods b) Derma/corium – a thick layer of living o Resistance to wear o Retanning – gives the required handles to
tissue below the epidermis o Resistance to heat & water Raw Materials:
used in Europe. the leather & modify the dyeing
is chemically resistant, allowing the o Ability to hold embossing
• In 1632, Bark tanning methods were introduced
epidermis to be easily removed by o Ability to absorb heat Animal Hides/Skins – Batangas & Cebu characteristics
by French in Canada & English in New England chemical means. o Porous are the main sources of hides in the Phils. o Dehairing – usually placed in a vat of
• In 18th century, Sir Humphry Davy – discovered c.) Flesh – is an extraneous layer of adipose Kinds of Leather
Sodium Sulphide – a sharpening agent warm water which permits easier removal
used in accelerating the dehairing process. of hair.
other barks that could be used for tanning aside tissue which must be removed to ensure
from oak & sumac. tannin penetration on both side of the Lime water – unhairing agent o Fat liquoring – it restores the fatty oils
1. Heavy Leather – for sole and belting
• In 19 century, Vegetable tanning, i.e., tanning
th corium. 3+
Chrome (Cr ) – exhibits a slight tanning Preservation – usually by salts to avoid
using the extracts from the bark of certain kinds
Infos: Sole leather – a vegetable tanned (good effect; source: Masinloc, district of decomposition of hides
of trees, was supplemented by chrome tanning. • Addition of hot water causes slow thickness & firmness). Zambales o Pickling – reduces the pH of the skin to
o “Chrome-tan leather” was introduced by solubilization to collagen when producing Light Sole leather – a vegetable tanned Chromic sulphate – exhibits a stronger between 2.0 to 2.5.
Augustus Schultz & Robert Foerderer, with the gelatin (pliability & suppleness). tanning effect. o Bating/deliming – uses ammonium sulfate
improvement of machinery made it possible to • Hair has large keratin which grows thru Insoling & Offal Leather – vegetable Formic acid – swelling agent in the soak or chloride for the removal & alteration of
produce leather cheaper. both the derma & epidermis. tanned, no fillers are necessary. water. certain proteins & for the improvement of
Belting Leather – made from high quality Sulfuric acid – used in regulating the pH &
the color of
Comparison of Skins & Leather: hides SKINS, KIPS, HIDES the grain
in the tanning process; a pickling acid
Leather –a material created through the tanning of Chrome belting leather – fat liquored, together with HCOOH. Falling –
Skins/Hides Leather (rxn. in bating), a reduction in the
hides and skins of animals that has been made pliable greater resistance to moisture & acid Atlasol – degreasing & wetting agent
degree of swelling of the protein
& resistant to decay thru the chemical treatment Soon lose vapors.
called tanning. Pliability pliability & Retains Pliability Syntans(Synthetic tanning agents) – constituents of the limed skin
become hard &
Chrome sole leather – for sport boots. condensation products of sulfonated
2. Light & Dressing leather - for boot uppers, phenols & formaldehyde, capable of Tannery Operations:
Types of Skins: brittle
harness & upholstery. converting animal skin to leather.
Extremely a. Pretanning process – non-leather making
• Skin – used as a generic word to denote skin from Permanence Putresce very permanent, not Bark-tanned uppers – a.) russet leather, if o Classification acc. to use: a.) Auxiliary constituents of the skin are removed
all kinds & sizes of animals. quickly attacked by finish is on the grain side b.) wax leather, tannins, b.) Complementary tannins, c.)
bacteria if finish is on the left side. Replacement tannins
b. Actual tanning process – skin is turned
1. Hides – skins from larger animals (weighs 34 lbs. Water Absorb water Possesses great Chrome tanned uppers – one-bath or two- Sodium Sulphate – prevents acid swelling.
up) resistance & are resistance to bath process tanned. sources: Nueva Viscaya
c. Post-tanning process – required color &
2. Kips - skins from half-grown animals of larger permeated water appearance is imparted into the leather.
varieties (weighs 5 lbs. in wet state) easily by it Combination tanned uppers – Fat Liquors
3. Skin – skins from smaller animals Are converted combination of chrome & vegetable Dye Stuffs – either powder or liquid
4. Cattle hides – most important source of leather Boiling water to gelatin by Attacked with Sodium Dichromate – main raw materials
raw materials hydration great difficulty Harness leather - for clothing, leggings… for tanning process
“geto” – graded,
Stuffing – is done by adding several “Life is good when we’re having fun”
Trimming coats of compounds cont’g clay, mineral
examined, trimmed, Rinsing Vat
salts, corn ugar @ 60°C. Prepared by: Juphil Lamanilao
o Chrome Tanning – usually subdivided
3 – 24 hrs flesh – removed by a into 2 processes which penetrate the hide
spiral bladed cylinder very rapidly
FINISHING OPERATIONS One bath process – using chromium
Beaming 1% sodium terasulfide – hastens sulfate
rehydration & produces more Dyeing Stuffing Splitting
Two-bath process – using sodium
uniform hydration. Drum Drum Machine
Liming requires 8 hrs. of continuous process
2% Na2S – sharpening oil
(3 -7 days) with the hides maintained between 2 to
dimethylamine, Jacking Bench 4 pH.
cyanide salts. o Oil tanning – an old method in which fish
Dehairin oil or other oil and fatty substances are
g or hand-scraped stocked, or pounded, into dried hide until
Machine they have replaced the natural moisture of
the original skin.
Scudding bench used principally to make chamois
(20 – 30 mins) H20
Preservation & Disinfection of Skins:
Rinsing Vat • Curing - a method of short term
Drenchin (Chrome Tanning)
o Brine curing – immersing it in a
Vat saturated brine solution
o Salt Curing - sprinkling it liberally on
organic acids (A) Pickling both sides with common salt.
pH 3.5 Drum requires 3 to 4 weeks @ 13°C
NaCl Salt Absorption
(B) Methods of Tanning:
30% HCl o Vegetable Tanning –used for heavy
leathers, for soles & belting
Tanning Vats 1st bath 2nd bath 2 Broad Groups:
(30 days) Catechols
usually done in 8x7 ft vats, 5 or 6 deep,
Na2Cr2O7.H2O containing tan liquors and hides.
away from weakest tanning liquors thru
Vat (60 days) liquors of increasing strength.
Drum to prevent complete plugging of the
Ratio (liquor/hide) = 4 to 6 lb
Drum Borax Bleaching – is done by using dilute
solutions of oxalic acid or acidified
solutions of sodium metabisulphite.