Tackiness

Condition of tackiness, which may be slight or may involve permanent sticking, sometimes develops in a finish after application. The use of too much plasticiser and the improper drying of base coats may be factors that cause tackiness.

Tailings

Partially exhausted, ground tanning material obtained when layer pits are emptied.

Tail-liquor

More or less exhausted suspender liquor to be run away from the bottom suspender pit.

Taint

Damage to the grain is very noticeable and is caused by putrefaction due to delays in curing or from insufficient salting. Also know as salt prick, grain slip, grain peeling. Salt prick is characterised by a superficial pitting effect; grain slip involves larger areas and grain peeling is extensive damage which may result in areas of the skin actually dissolving during the leather making process.

Take-up (v); taking up

For a material, to remove a dyestuff (or a dyeing auxiliary) from a solution.

Tallow

Fat, or adipose tissue, of cattle, sheep and goats.

Tamarisk (tamarix)

Ground leaves and twigs sometimes used as sumach adulterant.

Note: Tamarix africana.

Tan (colour)

Brownish colour resembling that of typical vegetable tanned leather.

Tan (v); tanning

Treating prepared hides or skins with suitable chemicals to give a fibrous product, imputrescible when wet, more or less soft and flexible when dry and capable of  being wetted and dried without loss of these properties.

Note: Hides and skins are composed of collagen in a fibrous structure. The aim of tanning is to form irreversible chemical crosslinks to the collagen matrix to prevent degradation by bacterial, chemical or thermal action. Commonly used tanning agents, applied individually or in combination, are chrome (III) salts, giving a typically blue coloured leather, synthetic tanning agents, and organic vegetable tannins which give a characteristic pale brown colour. Various other metallic products such as aluminium and zirconium are also available as tanning agents.

Tan cake

Blocks of compressed, and sometimes dried, spent tan for use as fuel in  boilers. 

Tannage

Term used in describing a special type of tanning method, such as chrome tannage, quick tannage.

Tanned

Converted into leather.

Tanner

People whose job is to convert animal hides or skins into leather by any process.

Tannery

An establishment where hides or skins are converted into crust, wet tanned or finished leather.

Tannin

General term for the active tanning principles contained in vegetable tanning materials.

Tannin balance

Distribution of the actual amount of tannin introduced into the tanning process in the finished leather (in the fixed and water-extractable forms), in the various liquors and somehow lost in process.

Tanning degree

Empirical way to evaluate the amount of tanning. It is expressed by the ratio between the total amount of organic tannins bound to the leather and the hide substance.

Tanning liquor

Solution of tanning agent.

Tanning process

Operation in leather manufacture involving the treatment of the prepared pelt with the tanning agent.

Tannin-non-tannin ratio

Relation between the tannin and the non-tannin contents of a vegetable tanning material, such as tannin per 100 parts non-tannin.

Tan-through

Penetrating and tanning the pelt completely. 

Taran

Tannin-containing root of Polygonum alpinum, growing in the Caucasus and the Altai mountains.

Taw (v); tawing

Converting to leather with a mixture of alum, or aluminium sulphate, salt, wheat flour and egg yolk.

Tawed leather

Leather prepared with a mixture of which the essential active ingredient is an aluminium salt, formerly, but not necessarily today, alum.

Note: Alum, salt, egg yolk and flour. The natural colour of the leather is white.

Tawing paste

Mixture of alum, or aluminium sulphate, salt, wheat flour and egg yolk for use in tawing or alum dressing.

TCMTB

See: (2-Thiocyanomethylthio)-Benzothiazole.

TDS

See: Total Dissolved Solids.

Tear

Caused by sharp objects on the living animal hide; damage during transit by hooks, forklift trucks, etc. Mechanical machine damage in tannery processing.

Telopeptide

Peptide located at the end of the collagen polypeptide chain. A non-helical region. Telopeptides are split-off, for example, by pepsin.

TEM

See: Transmission Electron Microscopy.

Tender grain

Grain surface which for some reason, such as excessive acidity of the leather, is easily damaged by pulling, bending and rubbing.

Tenderness

Tendency of a leather to break due to the fragility of the fibres or of the fibre texture.

Tensile strength

Measure or test of a material extended at a specific rate until the forces reach a predetermined value or until the material breaks. The tensile strength is recorded in Newtons per square millimetre and there are facilities for recording the percentage elongation caused by a specific load, and the percentage elongation at break.

Thermolysis

See: Pyrolysis.

Thermoplastic

Property of a polymeric substance which, under thermal influences, becomes soft and plastic.

Thermoplastic binder

Polymer binders used to achieve film-forming and impart required properties to finish coats.

Thickener

Auxiliary used in finish formulations to increase the viscosity.

Thin Layer Chromatography (TLC)

Chromatographing on thin layers of adsorbents rather than in columns; adsorbent can be alumina, silica gel, silicates, charcoals or cellulose.

Thinning agent

Auxiliary used in finish formulations to reduce the viscosity.

Thio compound unhairing

Removal of hair or wool from hides or skins by thio compounds.

Thirds

Class of hide or skin suffering from certain defects which are more or less closely defined and which depend upon the type of skin (cattle hide, calfskin, goatskin, etc.) and the country of origin; not necessarily the lowest grade.

Three dimensional weave

Interlacing, or running of the fibres and fibre bundles of the dermal tissue (dermis) in the three dimensions.

See: Structural features.

Threshold Limit Value (TLV)

Concentration threshold which is set specifically for each pollutant. Refers to the limit accepted in the atmosphere of a working area (workshop, etc.). Is expressed in ppm or in mg/m³.

Threshold Limit Value - Short Term Exposure Limit (TLV - STEL)

Refers to a permissible 15 minutes exposure in an atmosphere contaminated with a specific type of pollutant.

The concentration requirement must be fulfilled at any moment during the working period.

Threshold Limit Value - Time Weighted Average (TLV - TWA)

Refers to a permissible exposure in an atmosphere contaminated with a specific type of pollutant. 

Through-dyeing

Dyeing of a leather throughout its substance or whole thickness.

Through-dyeing ability

Ability of a dyestuff to dye leather throughout its substance or whole thickness.

Through-feed

Passing a material through a machine by a conveyor, for example, an automatic spraying machine. Also, machines such as fleshing machines that flesh the hide in one pass, straight through the machine, instead of reverse feed out.

Through-feed dryer

Drying of leather in cabinets or tunnels by a through-feed circulatory system.

Tick

Small blood-sucking insect living on the skin of animals. Causes small pits or scars over the animal’s skin.

Time lag

The time between the animal being flayed and the period when the preservation agent (for example, salt) becomes effective against the bacteria present in the hide or skin.

Tinctorial power

Measure of the relative colour strength of a dyestuff.

Tint

Stronger or weaker variety of a colour.

Tint (v); tinting

Alter the colour of a material slightly.

Tinting dyestuff

Dyestuff which gives a subtle alteration to the colour of a material.

Tip (v); tipping

Colour the natural or artificially produced protuberances and elevations on a leather surface.

Tip coloured mohair velours

Coarse long-haired suede, surface dyed, with the ends of the fibres of a different, usually lighter, colour to the base colour of the suede, produced by mechanically teasing the flesh side to lengthen the fibre.

Note: Also known as "Tip coloured shaggy suede".

Tip dyeing

Application of dye to natural or artificially produced protuberances on the leather surface by means of a firm pad.

Tip-reserve

Process for obtaining a two-tone effect on furskins by applying a “resist” to the tips of the hairs before dyeing.

Tissue

Association of large numbers of cells, fibres and other cell products in an animal or plant body, having a common origin and performing a specialised function. 

Note: Epithelial, connective, muscular, nervous and blood tissues.

TKN

See: Total Kjeldahl Nitrogen.

TLC

See: Thin Layer Chromatography.

TLV

See: Threshold Limit Value.

TLV- STEL

See: Threshold Limit Value - Short Term Exposure Limit.

TLV- TWA

See: Threshold Limit Value - Time Weighted Average.

To and fro rubbing

Test to evaluate the effect of rubbing a material such as leather with another (felt) with a “to and fro” alternating movement.

TOC

See: Total Organic Carbon.

Toggle (v) ; toggling

The straining and fixing of leather onto frames with toggles. The purpose is to dry leather keeping it under tension.

Toggle dryer

Dryer in which the leather is dried whilst held under tension on frames by toggles.

Tone (colour)

Net effect produced on the eye by the mixture of radiations reflected, emitted and/or scattered by a material.

Tone (v); toning

Adjust, correct or shade a colour, by subsequent addition of a dye.

Top (v); topping

Make a second application of the same, or another, dye on top of a previous dyeing.

Note: Cationic dyeing on top of an anionic dyeing.

Top coat

Final top coat applied in the finishing process.

Top grease

Finishing coating of a grease mixture applied to leather, to give it special properties, such as gloss, or waterproofness.

Total carbon emission

Emission to the atmosphere of organic compounds calculated in carbon equivalent.

Total Dissolved Solids (TDS)

Quantity of dry material in a solution after its filtration.

Total fatty acids

Content of higher fatty acids, free and combined, in a material.

Total Kjeldahl Nitrogen (TKN)

Determination of all nitrogen in a sample excluding ammonium nitrogen.

Total Organic Carbon (TOC)

Indicates the content of carbon linked to organic material by measuring the CO₂ after complete oxidation.

Total Solids (TS)

Total content of suspended and dissolved solids in a liquid or gas.

Total Suspended Solids (TSS)

Total nonfiltrable residue on a standard glass fibre filter dish, after filtration and drying at 103 °C to 105 °C for a minimum of 1 hour.

Toxic

Product or preparation which may lead to death or acute or chronical health injuries when inhaled, swallowed or absorbed through the skin in small quantities.

Toxic (reproductive)

Substances or preparations which, by inhalation, ingestion or in contact with the human skin, could increase the frequency of fatal non-hereditary effects for the offspring or undermine the reproductive capacity of humans.

Transfer finish

Thin film of transparent or pigmented polyurethane on a paper or other suitable carrier which can be transferred onto a leather surface previously coated with adhesive, by heat and pressure.

Transfer foil

Special ready-to-use finish film on a backing or carrying material to be transferred onto a leather surface. Note: Gold leather.

Transmission Electron Microscopy (TEM)

Type of electron microscopy in which the specimen transmits an electron beam focused on it, image contrasts are formed by the scattering of electrons out of the beam, and various magnetic lenses perform functions analogous to those of ordinary lenses in a light microscope.

Trapped moisture

Can occur in foam finishing systems. If the finish is dried at too high a temperature initially, a surface film may form, trapping moisture underneath.

Tray dyeing

Process of dyeing in which pairs of skins, placed flesh to flesh, are repeatedly drawn through a dye solution contained in a tray.

Trim (v); trimming

Cut away useless or unwanted material from the edges of raw or tanned hides or skins to give them a better shape.

Trimmings

Solid waste generated at the trimming step (tannery).

Trough dyeing

Dyeing process in which the skins, usually paired flesh to flesh, are repeatedly dipped into, and removed from, the dye liquor contained in a trough.

See: Immersion dyeing, Dip dyeing.

Ts

See: Shrinkage temperature.

TS

See: Total Solids.

TSS

See: Total Suspended Solids.

Tumble (v); tumbling

Subjection of hides, skins or leather to mechanical action in a revolving drum fitted internally with pegs or shelves, in the dry state, alone in the damp state or together with liquor, molten grease, etc.

Tunnel dryer

Dryer consisting of a long tunnel through which the leather is carried whilst subjected to a counter-current of heated air.

Turbidity

Gives an initial indication of the level of colloidal matter of organic and inorganic origin. It is judged either by comparing the sample with reference opalescent solutions or by measuring the limit of visibility.

Turkey tracks

Occurs in either forward or reverse mode of roller coating giving a pattern to the finish similar in configuration to that of the foot of a turkey. The main cause is the film-forming properties of the finish being incorrect.

Two-component polyurethane lacquer

Reactive polyurethane system. Polyester or polyether polyols are mixed with exactly measured quantities of a crosslinking agent such as isocyanate, aziridine or carbodiimide before application. The final reaction which forms polyurethane occurs on the leather surface.

Two-dimensional chromatography

Chromatographic technique (paper or Thin Layer Chromatography - TLC) in which the sample is resolved by standard procedures (ascending, descending or horizontal solvent movement) and then turned at right angles in a second solvent and resolved.

Two-tone effect

Showing two tones of colour.

Two-way suede

Long and soft, fibred suede leather made and finished to show the mark of a finger drawn across it.