C.I.E.

Commission Internationale d’Eclaraige (= I.C.I. International Committee of Illumination). This Commission defined some standard illuminants, and observers.

C.I.E. triangle (thrichromatic diagram)

C.I.E. trichromatic components, which represent the sensitivity of the eye to red, green and blue and defined the colorimetric reference observer.

C.I.E.L.A.B. co-ordinates system

CIELAB colour space is a system to represent the tristimulus values in which there is a plane (A-B) with the bright colours and a perpendicular axis (L) on which white-black is represented.

Calfskin

Skin from a young bovine animal not exceeding a certain weight, which varies from country to country.

Canaigre

Plant growing in Mexico and California, whose tuberous roots contain 18% to 43% tannin.

Note: Rumex hymenosepalus.

CAP

See: Common Agricultural Policy.

Cape leather

Originally a soft, grain gloving or clothing leather made from South African hair sheepskin; now any similar leather made from hair sheepskin, but not finished leather made from East Indian  native vegetable tanned hair sheepskin.

Carbon dioxide

A heavy, colourless, odourless gas, present in the atmosphere or formed by the burning of fuels. Carbon dioxide is also exhaled by animals and used by plants in photosynthesis. It is also produced during biomethanation.

Carbon dioxide deliming

Deliming by means of carbon dioxide.

Carcinogen

Substance or preparation which, by inhalation, ingestion or skin penetration is believed to cause cancer in humans.

Carding leather

Butt leather, vegetable (originally, oak bark) tanned, lightly curried and fairly flexible, for holding the steel wires that form the periphery of the cylinders on the carding machines used in the woollen industry.

Carpincho

Grain gloving leather with a grain pattern somewhat like that of peccary, made from the skin of a water rodent indigenous to Argentina, Uruguay and Brazil.

Note: One of the leathers commonly designated as Hogskin.

Cascalote

Pods of a tree found in Mexico.

Note: Caesalpina cacolaco.

Case hardening

Outer surfaces of the hide or skin are tanned too rapidly thus preventing the tan liquor reaching the interior of the skin. Excessive build up of tanning agent on the surface leads to hardening and even eventual cracking of the grain.

Casein

Protein obtained from skimmed milk by precipitation with hydrochloric acid and used in finishes. Dried casein is available in a great number of commercial products having different viscosities depending on their application and composition.

Catechin tannin

Strictly speaking a tannin somehow formed from a catechin

 (5 : 7 : 3’ : 4’ tetrahydroxyflavan – 3 – ol) unit ( gambier), but also sometimes applied to tannins formed from related units, such as a trihydroxyflavan-3-ol (quebracho) or a trihydroxyflavan-3-4-diol (mimosa).

Catechol tannin

Tannin presumed to contain a catechol nucleus because it gives a green colour with a ferric salt or yields fragments with a catechol nucleus on alkaline fusion.

Cationic dyestuff

Ion, molecule or radical from a dyestuff with a positive charge.

Cationic fatliquor

Ion, molecule or radical from a fatliquor (oil globules) with a positive charge.

Cationic resin

Ion, molecule or radical from a resin (organic substance) with a positive charge.

Cationic soap

Ion, molecule or radical from a cleansing substance with a positive charge.

Cationic surfactant

Ion, molecule or radical from a surfactant with a positive charge.

Cauliflower effect

Loss of substance during wet processing due to vertical fibre effect, leads to a “cauliflower” like pattern on the flesh side.

See: Vertical fibre.

Cellulose aceto butyrate lacquer

Film-forming product in finishes, abbreviated CAB. Good stability to yellowing on exposure to light and heat. Excellent fastness to migration and resistance to free amines of polyurethane foams.

Centrifugation

Partially separating sludge contained in water by means of centrifugal force.

CFC

See: Chloro Fluorocarbon.

Chain

Chain of molecules bound to each other to form a new chain. For example, a chain of amino acids to form a protein or a chain of monomers to form a polymer.

Chamois

Leather made from the flesh of sheep or lambskin, or from sheep or lambskin from which the grain has been removed by frizing, and tanned by processes involving the oxidation of fish or marine animal oils in the skin, using either solely such oils (full oil chamois) or firstly, aldehyde and then such oils (combination chamois).

Note: France and the USA restrict the term "chamois", without any qualification, to the flesh split of sheepskin tanned solely with oils.

In Germany the term "Sämischleder" is applied to an oil tanned suede leather made from sheep, lamb, roedeer, red deer, chamois, goat and kid skins and cattle hide splits.

In Italy and Switzerland this leather is incorrectly termed "pelle di daino" and "Hirschleder" respectively.

Chamois tannage

See: Oil tannage.

Chatter marks

Ridges in leather caused by fleshing, shaving or splitting machines where the cylinders are worn, poorly balanced or the bearings on the grinders may be worn. “Wire edges” on the cylinder will also cause chatter marks.

Chemical coagulation

Destabilisation of colloidal particles brought about by the addition of a chemical reagent known as a coagulant.

Chemical Oxygen Demand (COD)

Analytical determination of the amount of oxygen chemically consumed by the oxidation of the organic or oxidisable inorganic matter in an effluent. Potassium dichromate is used as oxidant.

Chilling

Hides chilled down immediately after flaying to between 8 °C and 10 °C can be stored over a week, as is done today in some areas for fresh hide processing. This chilling can be successfully achieved by distribution of shredded ice on the flesh side of the hides and storage in boxes. Dipping or spraying with chilled fresh water also can be used, and is also in current practice.

Chlorinated hydrocarbon

Organic substance (hydrocarbons) treated to combine with chlorine.

Chlorinated-paraffin wax

Solid, wax-like mixture of chlorinated higher paraffin hydrocarbons.

Chloro Fluorocarbon (CFC)

Any of a class of gaseous compounds of carbon, hydrogen, chlorine, and fluorine, used in refrigerants, aerosol propellants, etc., and harmful to the ozone layer in the earth's atmosphere owing to the release of chlorine on exposure to solar ultraviolet rays.

Cholesterol

Sterol produced by all vertebrate cells, particularly in the liver, skin and intestine. It is a component of the animal fatty materials.

Chondroitin sulphate

Nitrogenous  polysaccharide occurring in cartilage and in the interfibrillary material of hides and skins in the form of condroitinsulphuric acid.

Chromatic triangle

Triangular diagram with the three primary radiations (red, blue, green) placed at the corners. Mixing the primary colours, in varying proportions, it could produce all the colours.

Chromaticity

Quality of a colour which is defined by its dominant or complementary wavelength, taken together with its purity.

Chromatin

Protoplasmatic substance in a cell nucleus forming chromosomes, staining intensely with basic dyes.

Chromatogram

Result of chromatography. In Gas Chromatography (GC), High Performance Liquid Chromatography (HPLC) and Ion-exchange Chromatography (IC), it is a diagram where peaks represent different compounds separated by the chromatography from a mixture.

Chromatography

Method of separating and analysing mixtures of chemical substances. Note: Gel permeation, thin layer, ion-exchange, two-dimensional, absorption, ascending, column, descending, liquid, paper, partition. See: High Performance Liquid Chromatography (HPLC)

Chrome (v); chroming

Treat hides and skins with chrome liquor for tanning.

Chrome complex dyestuff

Anionic dyestuff containing metal chrome complexes, type 1:1 or 1:2.

Chrome complex, (chromium) (cationic, anionic, neutral)

Complex formed by the co-ordination of various ligands to one or more Cr⁺⁺⁺ ions, which may have a net positive (cationic), negative (anionic) or zero (neutral) charge.

Chrome leather

Leather tanned either solely with chromium salts or with chromium salts together with quite small amounts of some other tanning agent used merely to assist the chrome tanning process, and not in sufficient amount to alter the essential chrome-tanned character of the leather.

Chrome liquor

Basic chromium sulphate liquor prepared by reduction of a dichromate by glucose in the presence of sulphuric acid.

Chrome mordant dye

Dye, which  needs a mordant to fix.

Note: Chrome as a metallic salt could be a mordant.

Chrome oxide

Dark green, amorphous powder, forming hexagonal crystals on heating that are insoluble in water or acids; used as a pigment to colour wares and as a catalyst. Also known as chrome green.

The chromium content of a chrome tanned leather and of a chrome tanning material is usually expressed as chrome oxide (Cr₂O₃) content.

Chrome retanned leather

Second tannage treatment of a leather tanned with chrome tanning salt, and then with other tanning materials.

Note: As vegetable tanning.

Chrome stain

Irregular shaped darker coloured area on chrome leather, seen after tannage, due to increased deposition of chromium compounds, often related to too rapid basification.

Chrome tanning

Chrome tanning using a single solution of a basic trivalent chromium salt, usually primarily the sulphate.

Chrome tanning salt, (liquid; powder)

Commercial preparation of basic chromium sulphate, of a certain basicity, containing more or less of neutral salts; in the liquid, or powder, form.

Chrome-alum liquor

Basic chromium sulphate liquor prepared from chrome alum by addition of an alkaline substance, usually sodium carbonate.

Chromium

Metallic chemical element, symbol Cr, atomic number 24, atomic weight 51,996.

·    Hexavalent: the hexavalent form (Cr⁺⁶ or CrVI) of chromium ion as in chromates and bichromates. It has no tanning properties.

·    Trivalent: the trivalent form (Cr⁺³ or CrIII) of chromium ion as in chrome sulphate, chloride, etc. This is the chrome tanning form.

·    Total: The chromium content in leather, float, wastewaters, etc. in whatever form it is.

Chromophoric group

Group of atoms, such as –N=N-, -C=C-, =C=O, -N=O, in an organic substance which, when present in suitable structural positions, and in sufficient numbers, enables electron displacement to occur along the group or groups, and gives rise to colour.

Chrysoidine

Monoazoic basic dye.

CITES

CITES is an abbreviation for the Convention on International Trade in Endangered Species of Wild Fauna and Flora. Also known as the Washington Convention, as CITES was signed in Washington DC on 3 March 1973 and came into force on 1 July 1975. The purpose is to control the exploitation of wild animals and plant resources.

CITES has established a worldwide system of controls on international trade in threatened wild life and products derived from them by stipulating that government permits shall be required for such trade.

Clarifier

Settling tank  which allows activated sludge to be separated from purified water.

Clariflocculator

Device in which the floc is settled. The floc is obtained by agglomeration of destabilised particles into microfloc and later in bulky flocules.

Classification (for chemicals)

European classification of chemical substances or preparations explaining the risk associated with their use.

The possible classifications are : Explosive, Oxidising, Extremely flammable, Highly flammable, Very toxic, Toxic, Harmful, Corrosive, Irritant, Sensitising, Carcinogenic, Mutagenic, Reproductive toxic, Dangerous for the Environment.

Claws

Pointed, horny nails or protrusions, from the feet of certain animals and birds.

Clean (v); cleaning

Removing dirt, spots and impurities from the surface of a material. It may be performed dry and/or wet. For example, by solvent.

Cleanability

Ability of an upper or clothing leather to be maintained in a clean and good condition.

Clear (v); clearing

Cleanse the leather grain surface from grease, etc., prior to seasoning by rubbing over with a solution of ammonia or lactic acid.

Clear grain

Grain surface free from blemishes or stains.

Clear lacquer

Pigment-free transparent lacquer used in finishes, especially as top coating agent.

Clone (v); cloning

Create genetically identical copies of a population of organisms derived originally from a single individual. To clone an animal or a plant means to propagate or produce it as a clone, for example create genetically identical copies.

A clone is an animal or plant that has been produced artificially from the cells of another animal or plant, and is identical to the original one.

Closed grain

Tight formation of the surface grain on leather.

Clothing leather

Soft, flexible, non-stretchy, grain or suede leather of a thickness suitable for clothing. It may be made from full substance, or split, hides or skins and tanned in various ways. Note: It should be fast to light, perspiration and wet and dry rubbing and be capable of being washed or dry cleaned.

Cloudy

Visible uneven appearance caused by transparent or opaque whitish blush on the surface of the finished leather.

Clumping

Aggregation of small particles into larger ones, as a thick cluster, difficult to break up. This process occurs if an aqueous solution is added to a powder pigment instead of stirring the powder into the solution.

Coagulant

Soluble substance which under certain conditions, such as rise of temperature, pH alteration or chemical action, forms a semi-solid or jelly-like insoluble precipitate, which can carry along fine suspended solids.

Note: Ferrous sulphate, organic polyelectrolytes.

Coagulate (v); coagulating

Cause a substance in solution to separate out as large particles, or to change to an insoluble form and separate from solution as large aggregates.

Note: As do blood globulins when their solutions are heated.

Coagulation (of finishing products)

Finishing products are often susceptible to extreme temperatures. Frost will cause aqueous-based finishes and especially thermoplastic binders to coagulate irreversibly. Heat will cause irreversible coagulation of albumens and globulins.

Coagulation-flocculation

Process of injecting one or more chemical products with the objective of destabilising dispersed colloidal matter, aggregating it and then agglomerating it into large separable particles.

Coarse emulsion

Emulsion in which dispersed droplets are comparatively large.

Coarse grain

Grain surface that is somewhat rough, due to the nature of the pelt and the method of treatment during tannage etc., and in which the hair or wool follicles are large, forming a prominent pattern.

Coarse woolled

Sheep having long, strong, coarse fibre wool especially suitable for carpet manufacture, such as various large mutton breeds of English origin.

The impression of coarseness or fineness is given by the diameter of the individual fibre. The smaller the diameter the finer the fleece cover will feel. Coarse woolled  sheep breeds are covered with a low density wool coat of medullated ‘thick’ fibres that can have - in the coarsest types - a diameter over 38 ìm (1000 ìm= 1 mm). Comparatively, the finer wool types, such as merino, have a fibre diameter of approx. 18 ìm to 26 ìm.

Coarse-pored leather

Leather whose grain shows large pores which can be improved by buffing.

See: Fine-pored leather.

Coat (v); coating

Application of liquid system, such as a dye solution, or a pigmented finish, to a material such as leather.

See: Brushing; padding; spraying; curtain coating.

Cockle (Keds)

Defect on sheepskins (rib cockle), first recognisable after unhairing and appearing on the grain surface as small, firm nodules, usually over the butt, in lines running at right angles to the backbone towards the flanks. It is due to infestation by keds. Scatter or spread cockle is more diffusely spread over the skin and has been linked to lice.

Note: Ked - melophagus ovinus.

Coconut oil

Oil from the kernels of the fruit of the coconut palm.

COD

See: Chemical Oxygen Demand.

Coil

Continuous length of material in a spiral shape like the thread of a screw. For example, collagen helix.

Cold crack

Possible damage to a finish film when the leather is flexed at low temperatures. Shoe uppers, therefore, need cold crack stability.

Cold stuffing

Introduction of a mixture of oils, fats and waxes into damp leather at room temperature by hand, drumming or impregnation.

Cold sweating

Process of loosening the hair or wool of hides or skins by keeping them damp and cool (up to about 12 °C) so that bacteria develop and attack the hair roots and lower epidermal layer.

Cold-stable

Oil which does not deposit solid fatty matter on cooling to a specified temperature.

Collagen

Protein comprising the white fibres of vertebrate connective tissue, such as the dermis of skin, the matrix of bones and the dentine of teeth. Collagen is the leather making protein of the hide. Collagen in the hide or skin is perfectly structured to act as a protective covering for all animals and these same features are ideally suited for additional processing as an accessory for man (1997 IULTCS Congress, London).

Dermis, the leather giving layer of the hide or skin, after the removal of epidermis, hair and flesh layer, is almost entirely collagen. In the animal kingdom, this bio-polymer is unique in its amino acid composition, structural diversity and physical properties.

The basic structure of the collagen molecule is simple. The key to its ubiquitous presence is the ability of nature to modify this simple structure so that the biological diversity of the collagenous structures and their functions are unequalled by any other protein.

At the time of the Centenary Congress (1997) of the International Union of Leather Technologists and Chemists Societies (iultcs) in London, 19 genetically distinct collagens were known.

The fibres of the leather giving layer dermis are copolymers of the major type I - fibrous collagen,  together with minor amounts of collagen types III (fibrous), V (fibrous), VI (filamentous), and possibly XII (fibril associated collagen).

See:  Ageing;  amino acid; angle of weave; bond; dermis;  denaturation; structural features; hydroxyproline;  isoelectric point; grain layer; papillary layer; reticular layer; maturity; interfibrillary matter

Collagenase

Enzyme which hydrolyses collagen, a substance that accounts for 75% of the dry weight of skin tissue.

Colloidal suspension

Describes particles - often electrically charged - which are dispersed in a fluid but fail to settle naturally. This term is also used for fine suspended solids which settle only with considerable difficulty. They can be removed by coagulation - flocculation.

Colophony

Yellowish, glassy resin obtained as a residue from the distillation of turpentine, an exudation from certain pine trees.

Colour

Visual sensation produced on the eye by radiation of bodies or substances, reaching it after reflection or scattering by a surface or transmission through a material. These special characteristics depending upon the spectral composition of the wavelengths of radiant energy capable of stimulating the return and its associated neural mechanisms.

This sensation is defined by three characteristics: Value (or intensity), hue or tone, and croma.

Colour (v); colouring

Apply or give colour to a material, as by dyeing, painting or staining.

Colour base

Insoluble organic substance which, when dissolved in acid, gives a dyeing cation.

Colour change

Alteration in the colour of a coloured material produced by chemical treatment, alteration of pH, light, etc.

Colour circle

Circle designed to exhibit the proportion of primary colour in any shade of colour.

Colour levelness

Visible evenness of the coloured surface of a dyed or finished leather.

Colour matching

Application of an adequate blend of dyestuffs to a material, such as leather, to obtain and duplicate the same colour as that of a sample in any kind of material.

Colour shop

Place (zone, area, or department) where colour recipes are prepared.

Colour sorting

Classification of dyed skins with similar colour for making a leather garment.

Colour stripping

Lose the colour from a material, by chemical treatment or sunlight effect.

Colour triangle

Triangular diagram showing the three primary colours (red, green, blue) placed at the corners. Mixture of any two primaries will be found in the line joining the corners, and the centre of the triangle will, theoretically, be black..

Combination chamois

Chamois tanned by using aldehyde prior to fish or marine animal oils.

Combination oil tannage

Tannage in which the skin is treated with any suitable aldehyde, and then with an oxidisable marine mammal or fish oil.

Combination tannage

Tannage with two or more tanning agents of different types, usually applied separately in succession.

Combing leather

Strong, resilient, curried butt leather, free from permanent stretch, made into endless belts and used on machines for combing wool. It is chrome tanned (green) or combination tanned (brown).

Comets/spots

If pigment finishes are insufficiently mixed or filtered, a small spot of solid pigment can cause a streak under a plating, polishing or glazing machine.

Common Agricultural Policy (CAP)

Common Agricultural Policy of the European Union.

Compacting container

Skip equipped with a press in order to reduce the volume of solid waste it contains by increasing its density.

Compactness

Property of a leather with an internal structure of closely packed leather fibres.

Complementary colour

Either of a pair of spectrum colours which when combined give a sensation of white or nearly white light. One of two pigments whose mixture produces a third colour, as blue and yellow blended to produce green.

Compost

Soil amendment obtained from the biological aerobic treatment of waste containing organic matter. During  the biological treatment, the temperature naturally rises up to 60 °C, followed by a period of maturation, which stabilises the material. Before use, it usually has to be sieved.

See: Composting.

Compost heap

Composting technique in which waste is disposed in heap that is turned over to improve aeration.

Compost (v); composting

Production of compost by breaking down the organic matter contained in sludge or organic waste.

See: Compost.

Compressibility

Property of a substance capable of being reduced in volume by application of pressure.

Concentration

Amount of a chemical substance,  in a material, water, solid waste. It is generally expressed in %, mg/l, mg/kg or mg/kg dry solid.

Condensation tannage

Resin tannage in which insoluble high-molecular compounds are formed within the leather by inter-condensation of previously introduced methylol compounds of nitrogenous bases, such as urea, melamine, etc.

Condensed tannin

Tannin of the class which, in contrast to the tannins of the hydrolysable class, cannot be split into simple units by enzymes or dilute acids, its molecule being composed of polyphenol units joined by carbon-to-carbon linkages or carbon chains.

Condition (v); conditioning

After drying, the leather may be hard and of uneven moisture content. Moisture is re-introduced into the leather to a level that is suitable for subsequent mechanical actions such as staking or milling.

      The term is also used for bringing leather into equilibrium in a standard atmosphere before physical leather testing. Note: Test methods, IUP 3.

Conditioning plant

Plant able to keep pre-arranged conditions in a room or cabinet. Note: Humidity and temperature.

Connective tissue

Type of mammalian tissue, composed essentially of collagen, elastin and reticulin fibres, together with various types of cells, blood vessels, nerves, ground substance, etc., forming the dermis, areolar tissue, tendons, bones, walls of most organs, etc.

Conservation

Conservation means to increase the shelf life of a decomposable - putrecible- material, as, for example, the raw hide, by destroying the germs responsible for its decay (breakdown) or by retarding their growth (1922).

See: Curing; short-term curing; air drying; disinfectant.

Control guard

Guard associated with an interlocking device (with or without guard locking) so that :

- the hazardous part of the machine function is covered by the guard and cannot operate until the guard is closed

- closing the guard initiates operation of the hazardous part of the machine function(s).

Control of Substances Hazardous to Health (COSHH)

Control of Substances Hazardous to Health Regulations.

Conveyor

Mostly used as endless conveyor band to transport hides and skins or leather to or from a machine. In finishing, the conveyor band carries the flat leather through the spraying machines beneath the spray guns.

Cool (v); cooling

Become or make cool, or cooling  an object or a physico-chemical system by heat transfer to other cooler objects or systems.

Copolymerisation

Chemical reaction forming a polymer by mixing two or more monomers.

Cordovan

Originally a fine grain, coloured Spanish goatskin leather.

Cordovan

Leather made from the shell of a horse butt, that is from a kidney-shaped, very compact layer occurring in the butt of equine animals only, and isolated by removing the skin layer above and below it. It is vegetable tanned and curried.

Note: In Holland leather sold as "cordovan leather" is not necessarily made from horse hide.

Corium

Corium or dermis is the central layer of the hide or skin remaining after the removal of epidermis, hair and flesh (flesh side), and which is converted into leather. This layer amounts to approximately 95% to 98% of the total thickness of a hide or skin.

The dermis consists of an upper papillary zone (layer papillary) adjacent to the epidermis, and a lower reticular zone (layer reticular) which blends with the underlying adipose layer. Although no sharp line of demarcation is usually found between the zones, the boundary defined by the lowest hair or wool roots may be taken as the dividing line between the papillary and reticular zones. The papillary dermis is commonly referred to as the grain layer (also known as thermostatic layer), and the reticular dermis as the corium proper. The reticular dermis is the main layer of the hide or skin. This layer is composed mainly of interwoven collagen fibres arranged in well defined bundles.                            

The fibre bundles of the reticular dermis or ‘corium proper’ are relatively much larger than those of the grain. The structure of the reticular dermis which also varies with the species, age and sex of the animal is responsible for many of the characteristics of leather.

Corrected grain

Leather which has had the outer surface of the grain removed by an emery wheel to delete or “correct” blemishes. Also known as snuffed grain.

Cortex

Main structural component of hair and wool, covered by the scaly cuticle and consisting of cigar-shaped cells, arranged parallel to each other.

COSHH

See: Control of Substances Hazardous to Health.

Cotton dyestuff

Direct dyestuff able directly to dye cotton materials.

Counter

Stiffener or reinforcement in the back part of the shoe to retain shoe shape and offer stability and support to the heel of the foot. The counter may range from soft to rigid. It can be premoulded or flat and then moulded to the last by pressure.

Couple (v); coupling

Join by means of the azo group (-N=N-), the aromatic nuclei from two or more organic compounds.

Coupling dyestuff

Dyestuff which can be formed within a fibre by diazotisation treatment.

Cover

Poor covering of defects or colour irregularities on the leather surface. The cause can be type of pigment, colour of the leather, pigment to binder ratio and excessive penetration of the base coats. Poor cover of full grain leather may be due to damaged grain enamel, abraded grain, etc.

Covering power

Ability of pigments in the finish coat to cover irregularities on the surface of a leather.

Crack

Break appearing on the surface when a leather is under the strain of lasting, bending or pulling.

Crackiness

Tendency of a leather to crack. See: Cracky grain.

Cracky grain

Grain layer which breaks when the leather is pulled or bent. Grain crack could be caused by many factors such as chemical damage, poor lubrication, excessive tannage in the grain, etc.

Cream (v); creaming

Form a concentrated layer (thick oily, light-yellow substance) in a fatliquor, when the fatty globules rise to the surface.

Crease

Undesired fold marks in leather caused by improper handling during mechanical processes in leather manufacturing.

Crinkled patent

Soft patent leather with a creased or crumpled appearance produced mechanically after the patent finish has been applied and dried.

Note: Same as crushed patent.

Crock (v); crocking

Leather which is not colour fast when rubbed with a white cloth, wet or dry, is said to “crock”. The colour transfer may be due to loose dye and/or loose dust.

Crop (v); cropping

Cut the bellies from sole leather hides or sides after tanning in the layer vats.

Note: USA origin.

Cross coat

Coating formed by two successive applications of a liquid preparation at right-angles to each other. The term is usually applied to hand spraying.

Cross-breeding

To breed between two varieties of breeds of the same species. Breed crosses are very common; wool and mutton type sheep,  Zebu or Brahman cattle with European breeds, Criollo with Shorthorn, Angus with Hereford, Shorthorn x Angus x Hereford, etc.

The objectives of cross breeding seldom coincide with the need of the tanner for quality hides. Since its start, the main use of cross breeding has been the production of a commercial, more lucrative livestock.

Crosslink

Chemical links between the molecular chains of polymers.

Crosslinking agent

Highly reactive products like polyisocyanates or polyfunctional aziridine compounds to achieve film-forming properties of different finish formulations. Relevant safety regulations should be observed.

Crosslinking reaction

Process of joining free polymer chains with each other by side linkages to form a two or three dimensional network.

Crushed patent

See: Crinkled patent.

Crust (dyed) leather

Dyed leather dried out directly after postanning process.

Note: Vegetable, chrome or combination tanned.

Crust leather

Leather which, after tanning, has not been further processed but has been merely dried out.

Note:

In France the term "en croûte" is applied to any kind of hide or skin, such as "mouton en croûte, veau en croûte", and to any part of a hide, such as “collet en croûte, croûte en croûte”.

In the UK the term "crust" is used in connection chiefly with skins such as sheep, whilst the term "rough tanned" is similarly employed in connection with cattle hide leather.

In Italy, the term is also used for dyed and dried leather.

Culata

Italian and Austrian term for the rear part of a bovine hide, comprising the butt, the belly middles and the hind shanks (see figures J and K on the ‘International Glossary of Leather Terms - Schema’). French term for a more or less wide un-squared rear section of a cattle hide butt including the tail piece.

Cure (v); curing

Curing essentially consists of bringing about varying degrees of dehydration of the hide or skin either by simple drying or by salting; the curing salt itself acting as an additional inhibitor of putrefaction. As the percentage of hides put into work by the tanner within 24 hours of flaying is very small, the great majority of hides have to be preserved or ‘cured’ for transport and storage.

Cured weight

Weight of a hide or skin after curing by treatment with sodium chloride (wet-salting, brining) or other chemical or natural curative agent or process.

Curing salt

Common salt of appropriate composition and grain size for salting hides and skins. May contain denaturants or additives to improve its preservative properties.

Curried leather

Leather, usually vegetable tanned, which has been subject to the currying process, that is a series of dressing and finishing processes applied to leather after tanning, in the course of which appropriate amounts of oils and greases are incorporated in the leather to give it increased tensile strength, flexibility and water-resisting properties.

Curtain coating

Application of a liquid finish from a supply tank, in the form of a long, thin film, onto the leather surface as it passes on a conveyor through the curtain coating machine. Unspent float flows back into the supply tank and is continuously recirculated.

Cut

1. Inner part of a leather revealed by cutting perpendicular to the surface to examine for penetration of chemicals, dyes, etc. and for microscopical observation;

2. Cut produced by the knife on the flesh side of the hide due to bad flaying.

Cuticle

The hairs of most animals are of two types, primary and secondary. The primary hairs are the more numerous and are made up of three concentric cylinders, the medulla, an inner region of large columnar cells surrounded by a cylinder of smaller, spindle-shaped cells (the cortex), the whole being contained in the cuticle, a very thin layer of flat overlapping cells.

Cylinder plating

Continuous through-feed cylinder plating machine with the desired plating effect and film forming influenced by temperature and time of contact with the plating surface, as well as by pressure.