Sadden

Reduce the proportion of incident light reflected, scattered and/or emitted by a dyed material, by addition of a complementary colour in the dyeing mixture.

Saddlery leather

Leather used for all items of harness.

Note: Saddles, bridles, collars, etc.

Safety Data Sheet (SDS)

See: Material Safety Data Sheet.

Safety device

Device which eliminates or reduces risk, alone or associated with a guard.

Safety instructions

See: Health and safety instruction.

Saladero

1. In Spain and Latin America a slaughterhouse where meat is also prepared by drying or salting.

2. Saladero hide, a cattle hide from Argentina corresponding to the USA small packer.

Salt (v); salting

Any treatment of hides and skins with a salt for preservation.

Salt diffusion

Penetration of salt into the fibrous tissue of the hide or skin.

Salt shake-off

Removing loose salt and foreign material from a salted hide.

Salt spue

Soluble inorganic salts can give spue problems in finished leather. Perspiration on vegetable tanned insole leather can cause inorganic salts to migrate to the surface forming a crystalline spue. Inorganic salts used in chrome tanned leather, if not removed by thorough washing, can also give spues.

Salt stability

Ability to remain unaltered and stable by the addition or action of salts.

Salt uptake

Amount of salt taken up, or absorbed, when hides or skins are treated with salt.

Samm (v); samming

Bring leather to uniformly semi-dry state (approximately 50% to 60%  water content) necessary for certain finishing operations, by passing it through the sammying machine or by pressing.

Sample size

Physical dimensions, proportions, magnitude, or extent of a sample.

Sampling

Obtaining of small representative quantities of material for the purpose of analysis.

Sand/grit removal

Gravitational separation in wasterwater of gravel, sand and other materials whose density is higher than that of water.

Sandalwood

Certain trees of Santalum species or their woods.

Note: Santalum album (India), Santalum cygnorum (Western Australia); bark of latter contains 20% to 22% tannin.

Sandwich dyeing

A two or more staged dyeing process. Sandwich dyeing consists of changing the charge of the penetrated dyed leather before applying the second dye offer, which remains essentially on the surface. The second dye offer has an opposite charge to that of the leather.

Sanitary certificate

Document in which a sanitary fact is formally certified or attested. In the case of the leather industry, documentary evidence for the harmlessness from a health point of view of a batch of fresh or cured hides or skins.

Note: Freedom from anthrax.

Saponifiable fatty matter (grease)

Fatty matter which is capable of conversion to soap by the action of an alkali.

Saponify (v); saponification

Alkaline hydrolysis or decomposition of an ester to produce the components salt and alcohol which, in the cases of animal and vegetable oils, fats, and waxes, are respectively a soap and glycerol or a higher monohydric alcohol.

Saturated acid

Fatty acid derived from the saturated series of aliphatic hydrocarbons.

Saturated air

Air which is holding the maximum proportion of water vapour possible under the given temperature and pressure conditions.

Saturated brine

Saturated solution of sodium chloride; used for brining hides.

Saturated fatty acid

Fatty acid which has no double bonds in the carbon chain. Organic compound with the chemical formula C_n H_2n+1 COOH.

Sausage casings

Tubular material for sausage manufacture, made from intestines, disintegrated hide and skin pieces and splits.

Scab

Pimples caused by various bacterial attack eventually break and the exudate dries, giving a scab. Also refers to sheep scab - mange.

Note: Scabs found on leather as a result of severe scabies infestation.

Scald damage

Localised damage caused to hides or skins by direct contact with steam pipes or hot water.

Scalding

1. The action of burning with very hot liquid or steam

2. Wash and clean the carcass of an animal with boiling water, to remove hair, feathers, etc.

Scanning Electron Microscopy (SEM)

Type of electron microscopy in which a beam of electrons, a few hundred angstroms in diameter, systematically sweeps over the specimen; the intensity of secondary electrons generated at the point of impact of the beam on the specimen is measured and the resulting signal is fed into a cathode-ray-tube display which is scanned in synchronism with the scanning of the specimen.

It requires the vacuum pre-metallisation of the sample (usually by gold).

Scar tissue

Fibrous (more or less distorted) connective tissue of which scars (permanent marks left on the skin after the healing of a wound), are formed.

Scars - closed/healed

Scars caused by healed lesions of the hide or skin. This damage originally caused by mites, ticks, brands, scratches, etc.

Scars - open

Typically a scratch on the hide which has not yet healed. Any other infestation that has not yet healed to form a solid scar.

SCCP

See: Short Chain Chlorinated Paraffin.

Scour (v); scouring

Process of cleansing and/or smoothing a surface by abrasion, such as a heel or sole.

Scour (v);scouring

Washing/cleaning process for woolled sheepskins.

Scraper

A scraper bridge is used in a settler to bring the sludge in a specific zone of the settling tank ready for collection.

Scraps

Parings, shavings, cuttings, trimmings and other fragments of skin  or leather formed during the manufacture of leather or leather articles.

Scratch

Damage to the surface of the hide or skin caused by such things as barbed wire, inoculations, shearing, machinery within the tannery, etc.

Screening (fine or coarse)

Retention of solid matter of more or less large size with the help of a screen which is calibrated accordingly.

SCSCP

See: Short Chained Sulphochlorinated Paraffins.

Scud

Pasty mixture of hair fragments, lime soaps, fatty matters, etc., forced out of hide or skin by scudding.

Scud (v); scudding

Working over the grain surface of limed, or bated, pelt with a blunt-bladed tool, by hand or machine, to eliminate hair fragments, pigment granules, lime soaps and other impurities.

Scud defects

Improper removal of partially destroyed cells, hair roots, pigment and fats left in the hair pockets after soaking, liming and bating.  Scud that is not removed can lead to an uneven colour of the grain and, in the worst cases, roughness of the surface.

Scudding knife

Double–handled, concave, blunt knife, used on the grain side of dehaired hides and skins to work out hair fragments, pigment granules, lime soaps, etc.

Scuff marks

Grain enamel of the leather can be damaged by sharp or rough internal parts of tannery processing vessels. Scuff marks cause devaluation particularly of full grain leathers.

Note: Rough nails, bolts, splintered wood etc.

SDS

See: Safety Data Sheet.

Sea water damage

Damage caused to hides or skins during transport by sea from wetting with sea water.

Seal (v); sealing

Applying a special finish to seal the surface of the leather to assist further finishing. Also, this term is used to describe a protective top coat.

Seasoning

Application of a solution, based on film-forming materials such as albumen or casein, sometimes containing a dye or pigment, to give leather a protective coating, which may be more or less glossy or can be made so by glazing.

Sebum

Highly complex mixture of lipids (triglycerides and phospholipids) secreted by the sebaceous glands and epithelial waste which diffuses upward in the follicle and impregnates the hair and surrounding horny layers of the skin to participate in forming the greasy skin surface film.

See: Phospholipids.

Secotherm dryer

Dryer in which the leather is pasted on to the sides of a stainless, or enamelled, steel chamber maintained at 95 °C for chrome leather and at 50 °C for vegetable leather.

Sedimentation

Method for elimination of solids by the means of settling from a liquor.

Seed/grass

Seeds/grass caught in the wool of sheep. These can penetrate the grain causing permanent damage. Also lower the grade and value of the wool.

Self-basifying chrome powder

Mixture of a basic chromium sulphate powder and a slowly-dissolving alkaline compound, such as calcium or magnesium carbonate.

SEM

See: Scanning Electron Microscopy.

Semi-aniline leather

Leather which has been aniline dyed or stained, incorporating a small quantity of pigment, not so much as to conceal the natural characteristics of the hide.

Semi-chrome leather

Leather which has been tanned first with vegetable tannin and then re-tanned with chromium salts.

Note: In France, Holland and Italy it is used for a chrome/vegetable tannage.

Semi-chrome tannage

Vegetable tannage followed by a chrome tannage.

Semi-drying oil

Fatty oil, which could give a sticky and tacky film on exposure to air by homopolymerisation, with iodine value of 110 ± 10.

Semi-tanned leather

Leather which may not be sufficiently tanned to be satisfactory in use, though it may be stuck-through by the tanning agent, East India tanned sheep, goat skins, etc.

Semi-tannin

Organic constituent of a vegetable tanning material which may be taken up from an infusion made from it by hide or hide powder under certain conditions, such as in the filter bell method of analysis, but does not possess tanning properties; may be a phenolic tannin precursor.

Semi-Volatile Organic Compound (SVOC)

Semi-Volatile Organic Compound.

See: Volatile Organic Compound.

Sensitise (v) ; sensitising

Generally applied to chemical substances or preparations or even materials which, when in contact with the skin of a person or an animal, cause a skin irritation.

Set (v); setting out

Operation of working over the grain surface of wet leather to remove excess water, to eliminate wrinkles and granulations, to give the leather a good pattern and to work out stresses so that the leather lies flat.

Setting out pleats

Pleats, generally around the edges of the leather caused by incorrect setting out by machine. Can lead to extra trimming and loss of area yield.

Settling tank

Tank in which suspended solids and colloids (in the form of floc after coagulation-flocculation stage) are separated.

Sewage (raw)

Untreated wastewater which is discharged after domestic or industrial use.

Sewage system

Piping system used to transport untreated waste water to the effluent treatment plant.

Shade

Slight variation from a given colour.

Shade (v); shading (fur)

Dye the fur in such a way that the colour gradually decreases from the roots to the tips.

Shade dried

Dried by exposure to air whilst stretched on a frame and protected from the sun, such as in a shed.

See: Overdried; denatured protein.

Shading

Adjustment of shades according to leather samples.

Shadow finishing

Shading of certain parts of the leather in footwear and other leather products, usually by the leather manufacturer. Applies particularly to embossed leathers where a contrasting colour between the peaks and the valleys is achieved.

Shake method

Method to evaluate the tannins and non-tannins content in a liquid or a material (in solution) by measuring the amount of matter bound by the hide powder after shaking it together.

See: Non tannin (NT).

Shank

Flat, fingerlike slab of material inserted between outsole and insole to reinforce the raised area of the foot arch against body weight and stress. The shank may be in metal, wood, fibreglass, plastic or other material.

Shape-retention ability

Ability of a shoe to retain its original shape with wear.

Sharpen (v); sharpening

Intensify the action of a lime liquor upon hides or skins by addition of a chemical.

Shave (v); shaving

Reduce and/or level the thickness of leather, suitable for its intended end-use, by cutting fine, thin fragments from the flesh side by a machine with a rapidly revolving bladed cylinder (or by a suitable hand knife).

Shaved weight

Weight of tanned hides or skins after wet shaving.

Shavings

Small pieces of leather shaved off when the thickness of wet or dry tanned leather is rendered uniform by a bladed cylinder.

Shearing damage

Nicks or larger cut in the grain caused by shears used for clipping wool or cutting off dung from hides.

Shearling

Pelt of a woolled sheep, about one year old, slaughtered soon after shearing and bearing wool about ½ inch to 1 inch (1,0 cm to 2,5 cm) long or the tanned and dressed skin of a sheep still bearing the original wool which has been cut to an approximately even length. 

Sheepskin

1. 1. Leather from the unsplit skin of a sheep from which the hair or wool has been removed.

2. 2. Untanned outer covering of a mature ovine animal before removal of the hair or wool.

3. 3. Leather made from the skin of a wool sheep and still bearing the original wool.

Sheepskin prefleshing

Fleshing machine for the removal of fat deposits and the subcutaneous tissue (hydodermis, flesh layer) at an early stage during processing. Prefleshing is usually performed after soaking, as soon as the skins (especially air-dried sheepskins), are flexible enough to pass through the deburring machine for the removal of burrs.

Shellac

Non-thermoplastic film-forming material used for finishes. Coloured resinous substance, produced as an encrustation of tree bark by an insect. Note: Coccus lacca.

Shorn wool

Wool cut from the living sheep.

Short Chain Chlorinated Paraffin (SCCP)

Paraffin (organic hydrocarbonate substance) with the formula

R-Cl, where R group represents a short-chain alkyl radical containing between less than 14 carbon atoms, used as emulsifying or fatliquoring agents, to give softness to finished leather.

Short Chained Sulphochlorinated Paraffins (SCSCP)

Paraffin (organic hydrocarbonate substance) with the formula R-SO₂-Cl, where R group represents a short-chain alkyl radical containing between less than 14 carbon atoms, used as emulsifying or fatliquoring agents, to give softness to finished leather.

Short float unhairing, (Fasschwöde)

Unhairing in a short (low-water content) float.

Short Term Exposure Limit (STEL)

See: Threshold Limit Value - Short Term Exposure Limit.

Short term preservation

That period of preservation extending from hide or skin removal from the carcass to a week or two, or at best three weeks.

See:  Chilling; cool (v); cooling; icing; biocide; irradiation.

Short term curing

Treatment of hides and skins by a method which will preserve them for a few days only.

Note: Sufficiently long for transport from slaughterhouse to tannery.

Shoulder

Fore part of a cattle hide covering the shoulders and the neck of the animal, with or without the head. A squared shoulder is obtained by cutting off the head  including the cheeks and face.

Shoulder

Leather made from the fore part of a cattle hide covering the shoulders and the neck of the animal, with or without the head.

Shrinkage

Decrease in dimensions of skins, hides or leather produced by any cause, such as moist heat.

Shrinkage temperature (Ts)

Temperature at which a leather decreases in length and width (shrinks) when heated under specific conditions, for example, when heated in water.

Shrunken grain

Grain shrunken by a special beamhouse and tanning treatment that shrinks the leather to give the surface a unique fine-wrinkled effect. Used chiefly on kid, calf or other light leathers.

Shrunk-leather tannin

Very astringent tanning agent which produces considerable contraction of the grain.

Side

Half of a whole cattle hide with the attached offal  (head, shoulders and belly) obtained by dividing it along the line of the backbone.

Side leather

Shoe upper leather made from cattle hide sides.

Silica tannage

Tannage by means of an acid solution of metasilicic acid.

Silicate

Salt of an acid containing silicium and oxygen.

Silicofluoride (SSF)

Sodium silicofluoride (SSF), paste (12% moisture) or crystalline salt (Na₂SiF₆) used as an additive to salt in curing of hides, SSF prevents development of red heat, chromogenic and other bacteria. As an insecticide it is toxic or repellent to a wide range of insects including hide beetles and moths.

Silicone

Applied on dried leather, finished leather or leather products to impart water repellency.

Silk sheen

Silky suede with a two-way nap to give a plush appearance.

Silky suede

Suede leather with an especially silky sheen or gloss.

Silver leather

Leather with a silvery white, metallic lustre, produced by applying silver, or more commonly, aluminium leaf or an aluminium lacquer.

Single coloured

Hide or skin which has only one colour.

Sinker

Older form of layer, formed by half-filling a pit with tan liquor upon the surface of which a wooden grid (sinker) is floated. Hides are then spread, one by one upon the grid with shanks and head folded in, and each covered with a lesser or greater amount of ground tanning material until the pit is nearly full.

Skin

Tissue forming the outer covering of the body (human and other animal bodies), tough and flexible.

Skin grease

Broad term for the material extracted from dried skins by means of a fat solvent.

Skin wool

Wool removed from a sheepskin by the fellmongering process.

Skirting leather

Cattle hide leather, specially tanned and dressed for the skirts of saddles.

Skiver

Tanned outer or grain split of a sheep or lambskin.

Note: Sometimes applied to goatskin. In Germany and Spain the term is also used for the grain split of a raw sheep pelt.

Slaked lime

Lime which has been treated with a more or less excess of water to convert it to a pasty mass of calcium hydroxide.

Slate (v); slating

Work over the grain surface of delimed, or delimed and bated, hides and skins with a blunt, rectangular slate or stone tool to eliminate impurities.

Slats

Sheepskins dewoolled, usually by sweating, and dried out without tanning.

Sleeker (slicker)

Hand tool consisting of a blunt blade, usually of slate and sometimes set in a wooden, two-ended handle used for scudding skins.

Slink lamb

Tanned and dressed sheepskin bearing fine curly wool made from the pelt of a still-born or young lamb.

Slipe wool

A term for unscoured skin wool.

Slippery pelt

Pelt difficult to keep a firm grip on during such operations as fleshing.

Slippy hide

Raw hide whose hair, locally or all over its area, has become loose and easily removable by rubbing or scraping, owing to bacterial action which may have also caused other damage.

Slow-tanned sole leather

Light-weighing, unbleached, vegetable-tanned, cattle hide bottom leather, pit-tanned in cold liquors for up to 12 months (in the UK 5-6 months and in France usually 12 months), the process including layering for several months.

Note: In the UK and France, the basis of the process is oak bark and in Austria and Switzerland a combination of pine bark and oak.

Sludge

This generally refers to the residual sediment which results from wastewater treatment. The wastewater can be either urban or industrial.

Sludge (chrome)

Refers to the sludge obtain through the physical and chemical treatment of pretanning and tanning bath. Chromium concentration of the chrome sludge is generally above 50 g/kg dry matter.

Sludge cake

Sludge which has been partially dewatered by a filter press to the point where it can be handled easily.

Sludge drying bed

An open or covered area in which  wastewater sludge is dried by drainage and evaporation.

Sludge swelling

Phenomenon which results in excessive volume and poor settling of sludge in an activated sludge wastewater treatment plan. Biofilters are not affected by sludge swelling.

Sludge thickening

Initial treatment intended to increase the concentration of solids in sludge by removing water.

Smoke tannage

Tannage by treatment of pelts and fur skins with wood-fire smoke.

Smooth feel

Characteristic of the surface over which the fingers move without feeling irregularities of any kind.

Smooth grain

Grain having a smooth surface.

Snake skin

1. Skin of a snake, especially when used as leather.

2. Leather prepared from the skins of snakes.

Snow top

Woolled sheep or lambskins tanned and dressed with the wool on where the tip of the wool has been coloured by a deposition of a mixture of lead and antimony complexes.

Note: Snow top dyeing.

Snow top dyeing

Dyeing process which precipitates a mixture of lead and antimony complexes onto the wool. Disperse dyestuffs can replace the lead salt dyestuffs in order to avoid pollution.

Snuff (v); snuffing

Removal of a minimal thickness of the grain layer by abrasion.

Soak (v); soaking

Treating hides or skins with water, sometimes with the addition of an assistant or disinfectant, to cleanse them, remove salt and other soluble matter and to rehydrate and soften them.

Soak weight

Weight of rehydrated hide to maximum uptake of water and then drained to approximately 70% moisture.

Soak-back

Soak hides or skins, especially dried ones, in water, to restore, as far as possible, the original water content and softness.

Soda ash

White solid sodium carbonate (Na₂CO₃) with many applications in the beamhouse and tanning operations.

Sodium bicarbonate

Inorganic chemical (Na HCO₃), white powder, soluble in water, and faintly alkaline.

Sodium carbonate

Inorganic chemical (Na₂ CO₃), white powder, soluble in water, and mildly alkaline.

Sodium chloride

Colourless crystalline compound, NaCl, occurring naturally as halite and in sea water; common salt. Sodium chloride is used  in great quantities for the conservation of raw hides and skins and in leather making (pickling).

Sodium formate

Inorganic chemical (Na HCOO), with basic properties in water solution.

Sodium hydrosulphide

Chemical normally used in unhairing.

Sodium sulphide

Chemical normally used in unhairing.

Softening

Mechanical processes after drying such as staking or milling to achieve desired softness of leather.

Softy leather

Generic term for very soft and flexible upper leather.

Sole leather

Leather tanned and finished for the outsoles of footwear.

Note: In Italy it is vegetable tanned.

Sole leather bend

Leather made from the bend region of cattle hide, tanned and finished to be suitable for the outer soles of footwear.

See: Bend.

Solid waste

Material or object which is meant to be abandoned, destroyed or recycled.

Solo tanning agent

Chemical substance, extracted from plants or synthetically prepared, which, when used alone, is capable of converting pelt into usable leather.

Solvent

Liquid substance that is able to turn a solid substance into liquid. Special products are used in finish preparations to adjust the rate of evaporation which is necessary for film formation and to achieve desired finish properties.

Solvent fatliquoring

Introduction of a certain amount of lubricant into leather by drumming the damp leather with a comparatively high boiling point hydrocarbon solvent, such as naphtha, containing 0,5% to 1,0% of a highly-polar, water-insoluble agent, which remains after evaporation of the solvent.

Solvent free finish

Water soluble finishing systems. Solvent-based finishing systems, which cause ecological and health and safety problems, are rapidly being replaced by aqueous systems.

Solvent modifier

Organic liquid, such as toluene, which alone does not dissolve nitrocellulose, but in conjunction with a true solvent, such as alcohol, does so. Used to adjust the rate of evaporation.

Solvent soluble dyes

Metal complex dyes soluble in organic solvents used in finish preparations.

Solvent tannage

Treatment with vegetable tannins dissolved in organic solvents.

Solvent vapour

Vapour generated by a solvent or a solvent-based chemical.

Solvent-rubbing fastness

Ability to retain surface colour when rubbed with a cloth or pad wetted with solvent.

Sort (v); sorting

Select articles, and separate into groups with similar attributes or properties such as size, thickness, colour, etc.

Note: Classification of raw skins or dyed hides.

Sorting in colour

Sorting of dyed skins against a standard colour sample to ensure correct dyeing colour skin to skin.

Sour milk pickle

Liquor made from sour milk used for dressing certain skins, such as Astrakhan.

Sour tan

See: Acid tan.

SOx

See: Oxides of sulphur.

Speck

Very small damaged, or modified area on a hide or skin, of different colour, glossiness, etc., on leather, spoiling its appearance.

Speckled finish

Uneven and spotted appearance to the surface finish caused by incorrect atomisation of the pigment finish through the spray guns.

Spectrophotometer

Instrument that measures transmission or apparent reflectance of light as a function of wavelength.

Note: Visible, ultraviolet or infrared.

Spectrophotometry

Procedure  to measure photometrically the wavelength range of radiant energy absorbed by a sample under analysis.

Note: Near-infrared differential, infrared, raman, ultraviolet light, visible light, or x-rays.

Speed of  tanning

Rate at which a tanning process occurs, as measured by rate of penetration of the material into the hide, weight increase, etc.

Spent tan

Vegetable tanning material from which the tannin has been extracted.

Split (v); splitting

The operation of cutting a hide or skin horizontally into two or more layers.

Note: A grain and a flesh layer.

Split leather

Leather made from the outer (hair or grain) layer of a hide or skin from which the under, or flesh side, has split off to give a material of suitable and/or uniform thickness.

Note: Grain split or flesh split leather.

Splits

Leather made from the middle or under layer split from a hide or skin.

Spray (v); spraying

Apply a liquid in the form of very fine droplets.

Spray chamber

Enclosed compartment of a spraying line which houses the automatic spray guns, with a suitable exhaust system.

Spray dyeing

Dyeing with the application of a dyestuff solution in the form of very fine droplets with a spraying device, such as pistol or gun.

Spray finish

Most common application method for finishes using different spraying methods such as by means of compressed air or airless spraying.

Spray head

Unit in an automatic spraying plant which performs the spraying operation.

Spray jet

Fine orifice through which a liquid is passed to convert it to a spray of fine drops.

Spray nose

Finishing defect. Caused mainly by manual wet spraying of leathers hung up vertically. If the finish preparation has a low viscosity the wet coat begins to run after spraying, forming raised dye or film grooves which are named spray noses.

Spray specks

See: Speckled finish.

Spray staining

Application of a spray finish to colour the surface of undyed leather or to give improved levelness of drum dyed shades.

Spray streaks

Defect caused by irregular overlapping of the sprays of an automatic spraying machine. Correct adjustment of the spraying gun system and the conveyor speed will overcome the problem.

Spraying arm

Arm carrying the spray heads revolves above the leather travelling beneath it.

Spraying booth

An enclosure in which leather can be laid or suspended for manual spraying, fitted with an exhaust system for removing the spray vapour.

Spreading agent

Agent added to improve the liquidity of a finishing coat to obtain a coherent wet surface and improve flow-out.

Springbok

Medium-sized Southern African antelope, characterised by leaping into the air when fleeing.

Note: Antidorcas marsupials.

Spruce

Bark of common pine used in Germany and Central Europe to prepare larch extract.

Note:  Picea excelsa or vulgaris: Abies excelsa.

Spue (v); spueing

Exude, through pores, a substance from the interior to the surface of a leather.

Note: Solid inorganic salts or solid fats.

Square foot

Area of a square with a side of 30,48 cm (1 foot).

Note: 1 square foot = 0,0929 m².

Square metre

Area of a square with a side of 1 m.

Note: 1 m² = 10,764 square foot.

Squeakiness

Desirable property possessed by genuine Morocco leather of making a characteristic sound when crumbled. However, in other leathers, such as upholstery, this can be an undesirable characteristic.

Squeeze, (centrifuge)

Exert pressure on to a material, from opposite or all sides, especially to extract moisture from a material.

SS

See: Suspended solids.

SSF

See: Silicofluoride.

Stability

Property of a chemical compound which is not readily decomposed and does not react with other compounds.

Stack (v); stacking

Placing individual hides or skins, raw, in process or in the finished state, flat upon each other for storage transport, etc.

Stack curing

Method of curing hides by salting them down in a stack or pile.

Stacking marks

Marks resulting from piling hides or skins on top of each other, leading the outline of one skin to be imprinted onto the next skin. Often caused by piling leather that is too damp or making the piles too high.

Stain (v); staining

Colour the surface of leather by applying a dye solution to it by a brush or pad.

Stake (v); staking

Separate, soften and stretch the fibres of the leather by mechanical action, by hand or machine.

Staking wheel

A narrow revolving wheel, with a row of curved, blunt blades projecting radially from its circumference, used for staking.

Stale

Hide or skin which has undergone putrefactive damage owing to delayed curing, or prolonged storage, leading to such changes as the development of smell, hair-slip, deterioration of the corium, etc.

Staleness

See: Stale.

Stale-test

A test method to detect delayed cure in hides (post-mortem deterioration). The method depends on the action of proteolytic enzymes in the juice of the hide on the gelatin of photographic film, under standardised conditions.

Staling

Occurs when there is delayed or inadequate curing of raw hides. It can also occur in cured hides when there are poor and prolonged storage conditions. Staling leads to loss of substance, flankiness, pipiness, taint, veininess and poor break. The term staling is also sometimes used in connection with sheepskins, when they are subjected to the warm sweating process to loosen the wool.

Steam radiator

Heating radiator, utilising steam, often installed in drying tunnels, such as used in automatic spraying machines.

Steam sweating

Type of sweating process for depilating hides or skins in which the requisite conditions of humidity and temperature are maintained by injecting steam into the stove.

Steering wheel leather

Leather suitable for covering the rim of the steering wheel of an automobile.

STEL

See: Short Term Exposure Limit.

Stickiness

Undesired property of a finish coat to adhere to other solids. Especially a problem of thermoplastic binder systems which need heat treatment and pressure by plating for the required film formation.

Sticking

After the application of a surface finish, leather may be piled grain to grain and flesh to flesh. If the surface finish has not been dried sufficiently, the two grain surfaces may stick together. Separation causes damage to the finish and, in extreme cases, damage to the grain. This may also occur if the finish mixture contains binders that are too soft.

Stiffness

Characteristic of a leather which is quite rigid and therefore not very flexible.

Stillborn lambskin

Skin of a lamb, dead when born, with its wool on, used to make garments and gloves. See: Slink lamb.

Stirrup butt

Strong flexible leather usually 4 mm to 5,5 mm thick, as level in thickness as possible and with a close-shaved flesh.

Note: Made from ox hide rounded into butts approximately 5 ft. long (approximately 153 cm).

Stitch-tear

Resistance to tearing by a steel wire crossing two holes (stitch).

Stock (v); stocking

Subject skins to mechanical action by stocks in the chamois- making process.

Straight lime

Lime liquor prepared solely with lime.

Straight lime unhairing

Unhairing by the means of lime only.

Strain (v); straining

1. Stretch the skins out on wooden frames by strings attached to holes cut in the edges of the skins (shade dried).

2. To stretch and fix tanned hide or skin on a board or frame by nails, cords or toggles so that it can be dried under tension.

See: Toggle (v); toggling; belly strain.

Strain grain

Mechanical damage caused to skins when they are pulled from the carcass. See: Butcher strain.

Strap butt

Rough tanned or curried butt leather, made from cattle hide, of tannage and quality suitable for making into transmission belting.

Note: In Italy the term is usually applied to a tanned and well curried butt from which bands are cut which are used as accessories in weaving looms.

See: Crust leather; rough tanned leather.

Stretch (v); stretching

Wet leathers are stretched on frames for drying, such as toggling, to achieve maximum possible area yield. Subsequent softening and finishing processes such as staking and Dynavac will also increase area yield.

Stretchability of a coat

Soft leather has a great stretchability and therefore needs a coat which is flexible and can be stretched in the same way.

Striker

Metallic mordant, such as ferrous sulphate, used in dyeing with natural dyestuffs to develop the colour.

Striping effect

Spray pattern from a multi-gun spray machine is uneven and gives stripes of finish across the surface of the leather. It is caused by incorrect alignment and settings of the individual spray guns.

Struck-through

Penetrated throughout the thickness of the hide or skin by dyes or other agents.

Stuff (v); stuffing

Introduce a more or less solid mixture of oils, fats, waxes, etc., into leather by hand, drumming or impregnation.

Stuffed leather

Leather impregnated by hand or by drumming with a mixture of greases, waxes, oils, etc.

Stuffing drum

Drum, which can be heated by hot air, used for introducing grease in the molten state into damp leather.

Stuffing grease

Mixture of oils, fats and waxes and allied substances for application in the molten state to leather.

Stun marks

Mark on the grain caused by the use of a stun gun at the slaughter house.

Subcutaneous tissue

Tissue beneath the corium, connecting it loosely to the underlying body part.

Suede

Generic term for leathers whose wearing surface, either grain or flesh side, has been finished to have a more or less fine, velvet-like nap, produced by abrasive action.

Suede calf

Calf skin leather finished with a velvet-like nap on the flesh side.

See: Hunting calf.

Suede kid

Goat skin leather finished with a velvet-like nap on the flesh side. Full chrome tanned.

Suede shearling

Tanned and dressed sheepskin, bearing short wool, sueded on the flesh side.

See: Shearling.

Suede sheep

Sheepskin leather finished with a velvet-like nap on the flesh side.

Suede side or butt

Side or butt leather finished with a velvet-like nap on the flesh side.

Suede split

Leather made from the flesh splits of hide or skin and finished with a velvet-like nap.

Sueded grain

Grain enamel that has been damaged by bacterial, mechanical or chemical action. See: Low grain/rubbed grain.

Sueded woolled sheepskin

Sheepskin tanned and dressed with the wool on and finished on the flesh side with a characteristic velvet-like nap.

Suint

Dried perspiration of sheep deposited in the wool, chiefly in combination with fatty acids, that is rich in potassium salts. Most of the suint is removed during wool scouring.

Sulphated fatty alcohol

Sulphuric acid ester of a higher fatty alcohol, saturated and unsaturated.

Sulphated oil

Fatty oil rendered soluble or emulsifiable in water by treatment with concentrated sulphuric acid, washing and partial neutralisation; contains -C-O-SO₃H groups. Often termed as sulphonated oil.

Sulphation

Introduction of O–SO₃H groups, and to a minor extent of –SO₃H groups, generally into glyceride and fatty acid molecules of certain animal and vegetable oils by treatment with concentrated sulphuric acid, in order to make them self-emulsifiable.

Sulphato group

Anionic inorganic group ( -SO₄^2- ) held in a complex with water, amine or with other cationic forms, to form salts.

Sulphide oxidation tank

Aerated tank for the oxidation of sulphides with a catalyst (manganese sulphate).

Sulphitation

Treatment of a product, such as animal and vegetable oils and synthetic oils, with sulphite or bisulphite to render it water soluble or emulsifiable.

Sulphited alcohol

Alcohol treated with bisulphite or sulphite.

Sulphited oil

Water emulsifiable oil obtained by treating an unsaturated fatty oil with bisulphite and atmospheric oxygen.

Sulphochlorinated oil

Sulphonated long chain chlorine-containing oil.

Sulphochlorinated paraffin

Paraffin hydrocarbon R-X, where the X group is –SO₂Cl, introduced by chemical treatment with SO₃ and Cl₂ .

Sulphonated

Introduction of –C-SO₃H groups into a material.

Note: Applied to sulphated oils.

Sulphonated basic dyes

Amphoteric dye, depending on the pH it may have cationic charge at low pH or anionic charge at high pH. About pH 3,0 (iso-electric point) it has no charge and thus would give good penetration and levelness.

Sulphonated oil

Fatty oil into which -C-SO₃H groups have been introduced; term often applied to sulphated oils.

Sulphonation

Introduction of sulphonic acid group or its salts (–SO₃H) into organic compounds by the action of concentrated sulphuric acid, SO₃ or another chemicals, but often applied to the treatment of oils, with sulphuric acid to render them emulsifiable, or soluble, in water.

Sulphonic acid group

Group –SO₃H which can be introduced into organic compounds by the action of concentrated sulphuric acid, SO₃ or similar.

Sulphonyl chloride paraffin

Paraffin hydrocarbon into which the –SO₂Cl group has been introduced.

Sulphonyl chloride tannage

Tannage by means of alkyl sulphonyl chlorides.

Sulphonyl chloride tannin

Paraffin hydrocarbon into which the –SO₂Cl group has been introduced with tanning properties.

Sulphur dioxide

Sulphur dioxide is a colourless, pungent gas used in the manufacture of chrome tanning compounds, and has been tested as the active preservative agent for the short (2-3 days) preservation of the so called (USA) “sanitised” or “fresh type” hides.

Sulphur dyestuff

Sulphur-containing dyestuff, made by fusion of aromatic amines or phenols with sulphur or alkaline polysulphide, which is only soluble in an alkaline solution of sodium sulphide (pH 9-12).

Sulphur tannage 

Process of depositing colloidal sulphur within pelt by treating it with an acidified solution of sodium thiosulphate; used in conjunction with other tanning and dressing treatments, such as followed by treatment with grease and vegetable tannin in the Melior process for picking band leather.

Sumach

Ground leaves of some certain species of Rhus.

Note: Rhus coriaria (Sicily, Cyprus, Spain and other Mediterranean countries), Rhus glabra and copallina (USA) and Rhus cotinus (North Italy, Dalmatia, southern Hungary).

Surface appearance

Visible surface properties of a finished leather such as shade, lustre, colour, smoothness, grain pattern etc.

Surface dyeing

Dyeing confined to the surface of leather.

Note: Dyeing on grain (full leather), flesh or splits.

Surface fatting

Application of oil or grease to the outer surface of leather.

Surface handle

Physical surface properties of a finished leather, conveyed by feeling through the fingers and hands, such as flexibility, greasy feel, smooth feel, velvety feel, round feel etc.

Surfactant

Substance introduced into a liquid to alter (usually to increase) its spreading, wetting and similar properties (particularly properties depending on surface tension); can cause foaming and hinder biological activity.

Surfactant effect

Effect produced by a substance introduced into a liquid to alter (usually to increase) its spreading, wetting and similar properties.

Note: Properties depending on surface tension at the interface.

Suspended matter

All suspended matter in water that is large enough to be retained on a filter with a given porosity.

Mass concentration contained in a liquid. It is usually determined by filtration or centrifugation and drying in precisely defined conditions. Usually indicated in mg/l or g/m³.

Suspended solids (SS)

Mixture of fine, non-settling particles of any solid within a liquid or gas, the particles being the dispersed phase, while the suspending medium is the continuous phase.

Suspender

Pit, or vessel, containing a weak, more or less exhausted vegetable tanning liquor in which hides are suspended during the preliminary stage of tanning heavy leather.

SVOC

See: Semi-Volatile Organic Compound.

Sweat (v); sweating

Process for loosening the attachment of the hair or wool of hides or skins by maintaining them under such conditions of warmth and moisture that bacteria develop and attack the hair roots and lower epidermal layer.

Sweat chamber

Chamber in which the temperature and humidity can, if desired, be controlled and in which hides or skins are suspended so that bacteria develop and loosen the hair or wool.

Sweated hair

Hair removed from hides or skins after loosening by subjection to the sweating process.

Sweated wool

Wool removed from the sheepskin after loosening by the sweating process.

See:  Cold sweating; warm sweating.

Sweating damage

Sweating is the process for loosening wool or hair in warm, moist conditions where bacteria develop and attack the hair roots and epidermal layer. Unless carefully controlled, further damage can be caused to the skin by increased bacterial activity.

Swedish scheme

Cattle hide improvement project. Farmers that have joined the “Faultless Hide Scheme” apply a programme of measures to improve hide quality and prevent grain damage. The farmers are then paid for the improved quality that they achieve.

Sweet tan liquor

Vegetable tan liquor which has not fermented and developed acid.

Swell (v); swelling

Increase in volume owing to the absorption of a solvent, usually water.

Swell leather

Butt leather, vegetable tanned or chrome tanned, of uniform thickness, processed to give it heat or abrasion resistance. Acts as a friction brake in a loom shuttle box. Also known in North America as “binder leather”.

Swellable

Ability of a material, such as a finish film, to be able to increase in volume by absorption of water or other solvent, present in liquid form or in an underlying layer.

Swelling and plumping

Increase in volume and the development of rigidity and resistance to compression occurring when a hide or skin is immersed in dilute acid or alkali.

Swelling pressure

Pressure required to prevent a solvent, such as water, entering material, and causing it to swell.

Note: Water into gelatine or collagen fibre.

Swelling resistance

Ability of a finished leather surface to resist swelling in contact with water or a solvent.

Syntan

Abbreviation of the term synthetic tannin. Generally, these are prepared as salts of polyphenolic-sulphonic acids, from different simple phenols or from natural phenolic compounds (as lignosulphonates) by sulphonation and condensation.

Syntan retannage

Second tannage of a leather with syntans.

Syntan tannage

Generic term for various types of synthetic tanning agents that are used either before or after the main tannage to impart specific characteristics to the leather.

Synthetic grease

More or less solid, grease-like material, suitable for stuffing leather, based on synthetic materials.

Synthetic moellon

Water-in-oil emulsion, containing marine oil oxidation products, made by blowing air through marine oil at a slightly elevated temperature and adding water.

Synthetic neatsfoot oil

Oil for use in place of neatsfoot oil, based upon several synthetic chemical compounds.

Synthetic oil

Oil which is produced by organic chemical synthesis.

Synthetic resin

Artificially prepared organic material of high molecular weight, capable of being moulded under the action of heat and/or pressure and made by the polymerisation and/or condensation of simpler molecules.

Synthetic tannin

Misnomer for an artificial tannin,  aromatic, or aliphatic material capable of converting animal skin into a product more or less resembling leather; includes materials which, when used alone, can produce commercial leather, some resembling vegetable-tanned leathers as originally intended (replacement tannins), as well as others for use with vegetable tannins (auxiliary tannins).

Synthetic wax

Solid, organic material, obtained by chemical synthesis. A substance which may consist of a mixture of hydrocarbons or of esters, which has low melting point, insoluble in, and lighter than, water, soluble in organic solvents, and having a slightly greasy feel.