Alphabetical Search

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AAS	See: Atomic Absorption Spectroscopy.
Abatement	Reduce the quantity or toxicity of waste being generated by modifications to the process and by recycling.
Abraded grain	Grain enamel that has been damaged by bacterial, mechanical or chemical action. See: Low grain, blind grain.
Abrasion	Removal of surface material from any solid through the frictional action of another solid, a liquid, a gas, or combination thereof.
Abrasive paper	Paper coated with abrasive powder used for machine buffing of leather.
Abscess	Localised infection over lesions in the skin or hide, sometimes covered with a scab.
Absorptive power	Capability of a material (dye, levelling agent, grease) to be taken up by the fabric.
Acer tannin	Crystalline digalloyl hexitol, without tanning properties, isolated from the leaves of Acer ginnala.
Acid dyestuff	Water-soluble anionic dyestuff that is applied to nitrogenous fibres such as leather, wool, silk, nylon and modified acrylic fibres from acid or neutral baths.
Acid tan	Partially spent vegetable tanning material, removed from the old-fashioned layer pits , which has become acid owing to fermentation and is leached to prepare suspender liquors.
Acid residue	Part of an acid linked in a compound.
Acid-salt ratio	Ratio of total salts to total free acids in a vegetable tan liquor.
Acrylic binder	Thermoplastic binder based on polyacrylates. Used as film-forming material for polymer or binder finishes.
Additive	General term for all auxiliaries used in finish formulations.
Adhesion	Measure of the ability of a film of finish to resist being peeled away from the surface of the leather to which it has been applied.
Adhesive	Substance used to bond two or more solids so that they act or can be used as a single piece; examples are resins, glue, paste, cement, putty and polyvinyl resin emulsions. In the footwear industry it is known as cement and it is used to bond the outsole or linings to the upper.
Adhesive power	Ability of a finish to hold firmly onto the leather or another coating.
Adhesive strip test	Empiric evaluation of the adhesion of the finishing layer by applying a strip of adhesive paper on the finished surface of the leather and tearing it away rapidly.
Adipose tissue	Form of connective tissue in whose cell fat is deposited and stored. More frequently found in the  flesh layer of the hide or skin. See: Double hiding; fatty spue; fatty stain; grease mark; degrease (v); degreasing.
Adsorbable Organic Halogens Compounds (AOX)	Chemical organic halogen compounds that are adsorbed to surfaces or materials.
Adsorption	Retention of molecules or substances on the surface of a solid. Pollutant elements can be adsorbed. Should not be confused with absorption.
Aerated lagooning	A biological process for treating wastewater by sending it to a basin or lagoon that is aerated to ensure an oxygen supply sufficient for biological purification. A distinction is drawn between strict aerobic lagoons and facultative aerobic lagoons. In the first, all sedimentation is avoided by maintaining a high enough level of aeration. In the second, the oxygen input ensures biological activity but cannot keep all of the matter present suspended.
Aeration	Introduction of oxygen into water or effluent streams by bringing the water or effluent into intimate contact with air.
Aeration tank	Tank in which aeration is performed for the biological aerobic treatment of an effluent.
Aerator	Surface aerator intended to aerate water through a surface mixing. The two main types are : - vertical axis type (takes water and sprays it laterally into the air) - horizontal axis type (sweeps the water with a submerged portion of blades).
Aerobic sludge digestion	Describes a condition in which dissolved oxygen is present.
Aerobiosis	A biological process in which the presence of dissolved oxygen is necessary for the respiration of the micro-organisms.
Agate cylinder	Glazing cylinder in a glazing machine to develop a high gloss to previously seasoned leather.
Ageing	1. To store leather to allow tanning agent to become more firmly fixed. 2.  Changes that occur during the use of the material over a period of time. For example, caused by heat, ultra violet or artificial ageing processes.
Agent	Generic term covering many different materials used in processing hides and skins through to finished leather.  See: Levelling agent; fixing agent.
Air blast	Blowing (in) compressed air, such as air-blast dedusting machine. See: Dedust (v); dedusting.
Air bubbles	Entrapped air beneath the finish surface.
Air circulation	System of circulating air continuously round a drying unit, often for several times, before being extracted.
Air drying	Drying of hides, skins or finished leather by exposure to the air until equilibrium is reached.
Air permeability	Ability of a membrane or other material to permit air to pass through it.
Air scrubber	Device used to purify the air with circulating water, such as used in automatic spraying machine cabinets.
Airless spraying	Application technique of finish. In this system the liquid finish is ejected from the spray gun under pressure without air, giving a much heavier spray coat with less bounce-off or waste.
Albumin	Any of a group of plant and animal proteins which are soluble in water and dilute salt solutions and are coagulated by heat.
Alcohol	General term for different alcohols, organic chemical compounds containing the -OH group, used in finish formulations as solvents or diluents.
Aldehyde	One of a class of organic compounds containing the -CHO group.
Aldehyde retannage	Second tanning treatment, with an aldehyde R-CHO, of an already tanned leather, to modify its properties, using an agent of the same or an entirely different type.
Aldehyde tannage	Tannage with an aldehyde, such as glutaraldehyde or modified glutaraldehyde, usually in combination with other tanning materials.
Alkali	Any chemical (salt or mixture) that neutralises acids.
Alkyl phenol ethoxylates (APE)	Chemical group which includes nonyl phenol ethoxylates such as emulsifiers.
Alkylation	Chemical process in which an alkyl radical is introduced into an organic compound by substitution or addition. For example, if the      -CH3 group is introduced the process is defined methylation.
Alum retanned	Second tanning treatment, with double sulphates formed from one of the alkali metals combined with a trivalent metal, usually potassium alum and salt, but sometimes with aluminium sulphate and salt.
Alum tanning	Process of converting skins to leather based essentially upon the use, strictly speaking, of potassium alum, but sometimes of aluminium sulphate.
Aluminium tanned	Converted to leather with an aluminium salt.
Amine unhairing	Removal of hair or wool from hides or skins by amines.
Amino acid	Any of the organic compounds that contain one or more basic amino groups and one or more acidic carboxyl groups. Many amino acids are polymerised to form peptides and proteins; examples are tyrosine and lysine.
Amphoteric dyestuff	Dyestuff which can exhibit the characteristics of either an acid or a base, and could ionise as a coloured cation or anion, according to the pH.
Amphoteric tannin	Synthetic organic tanning agent, prepared by condensation of polyhydroxyphenols with aldehydes and bases, possessing both basic groups and acid phenolic groups; acts in acid solution as a cationic tannin.
Anaerobic sludge digestion	Biological reaction for sludge under anaerobic condition (lack of oxygen), producing mainly methane (CH4) and C02 and stabilised sludge.
Anaerobiosis	A biological process in which the reactions occur in the absence of dissolved oxygen; only chemically bound oxygen is used for the respiration of the micro-organisms. This species of micro-organisms is said to be anaerobic.
Angle of weave	Fibre pattern within the hide or skin. Can be genetic or process related. Horizontal fibre defect is where the corium fibres are orientated horizontal to the grain surface and are parallel and not interlaced. Vertical fibre defect is where fibres passing from the epidermal layer to the corium are orientated vertically to the grain surface.
Aniline	Colourless oily compound, C6H5 NH2, the base used in the formation of many rich dyes obtained from coal tar but more extensively from benzole; also the base for resins and varnishes.
Aniline dye	Synthetic dye based on aniline.
Aniline finish	Dyed leather without any pigmented coat. A transparent top coat may be added but the natural appearance of the grain should remain visible.
Anionic dyestuff	Ion, molecule or radical from a dyestuff with a negative charge.
Anionic fatliquor	Ion, molecule or radical from a fatliquor (oil globules) with a negative charge.
Anionic resin	Ion, molecule or radical from a resin (organic substance) with a negative charge.
Anionic surfactant	Ion, molecule or radical from a surfactant with a negative charge.
Anoxia	Describes a condition in which oxygen is absent and where nitrites and nitrates are present.
Ante mortem	1. Made shortly before death, for instance injuries in the slaughterhouse during unloading from the transporting trucks, etc. 2. Ante mortem is very often used to designate skin and hide damage factors occurring ‘long’ before the animals death. Note: Health issues such as ectoparasites.
Anti-auxochrome group	Any radical or group, such as –NO, -NO2 or C=O, in a coloured organic substance which can accept electrons.
Anti-friction agent	Finishing auxiliary such as silicone based modifiers, used to improve the surface feel of the leather. Note: Silky, slippy feel to garment leather.
Antique grain	Finishing method for achieving irregular two-tone effects to give the grain side of the leather an appearance of age and usage. The leather receives a raised embossed grain and after application of a wax resist it is treated with a second, mostly darker graining colour. The recessed parts will then have a darker shade in comparison to the raised parts.
Antiseptic	Compound that can be applied to and remain on the surface of the skin or mucosa and kill or inhibit the growth of infection-causing micro-organisms.
Anti-sticking agent	Used to reduce tackiness of the finishing coat and assist hot plating, embossing or ironing.
AOX	See: Adsorbable Organic Halogens Compounds.
APE	See: Alkyl phenol ethoxylate.
Apparel leather	See: Clothing leather.
Apparent density	Ratio between the mass and the volume of a substance including both the structure and the enclosed air spaces. Note: The interfibrillary spaces between fibres in the leather.
Apron leather	Leather for protective aprons for smiths, foundry workers, draymen, etc. Note: Vegetable or chrome tanned, stout, large sheep and pigskins, kips and cattle hide splits.
Aqueous emulsion	Dispersion of one liquid, such as oil, throughout water in which it is insoluble.
Area contraction	Shrinkage in the area of a leather.
Area loss	See: Area contraction.
Area measurement	Measurement of the area of a leather or hide or skin. The area is expressed in m2 (square metres) or in dm2 (square decimetres). The traditional method, still widely used, is to express the area in square feet (sq. ft. = 30.48 x 30.48 cm2).
Aromatic amine	Organic compound that contains one or more amino groups joined to an aromatic structure.
Artificial grain	Grain appearance given to a flesh split or buffed grain by pigment finishing with or without embossing.
Aryl amine	See: Aromatic amine.
ASA-leather	In Austria and Germany the common abbreviation for leather for the production of protective articles used in leather industry (Arbeiter-Schutzartikel=ASA), usually made of chrome tanned cattle hide leather.
Ash	Residue of a material after total combustion. It is generally used to characterise a solid waste and is expressed in % of the raw material.
Assortment	Collection of hides or skins having approximately the same desired characteristics. Note: Weight, freedom of defects.
Astringency	Property of a tanning agent to combine rapidly with the hide substance, leading to a contraction of the structure of the hide. This term is often used to describe the properties of a vegetable tanning solution.
Atomic Absorption Spectroscopy (AAS )	Measurement of the concentration of a metal ion in a solution. It is the measurement of the amount of a light energy of a known wavelength absorbed by the metal atoms vaporised in a flame. The wavelength of the light to be used is specific for each metal. The measurement is independent of the ionic form of the metal in the solution.
Auto inflammation temperature	Minimum temperature at which a liquid can inflame without additional energy.
Autolysis	Self-digestion process, causing damage to the hide structure due to enzyme action and occurring if curing is delayed too long after flaying.
Automotive leather	Upholstery leather for car seats and other internal parts of the interior design. Note: These leathers must meet specific requirements, such as fogging tests.
Auxiliary (synthetic) tannin	Synthetic tannin not suitable for use alone as a tanning agent, but designed for use with vegetable tannins to assist tannage, for instance to accelerate penetration, or to improve the leather, such as its colour.
Auxochrome group	Group, such as –NH2 or –OH, in a coloured organic substance which can donate electrons; any of certain radicals, which will convert a chromophore into an acidic or basic dye suitable for use in leather and textile fabrics.
Azo dye	Dye produced on the basis of an aromatic amine.

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