The Language of the Leather

Vegetable tanning is the oldest method of turning a raw hide into lasting leather, worked with tannins drawn from the bark, wood, leaves and fruits of plants rather than with mineral salts. The process is slow, traditionally a matter of weeks, as the tannins penetrate the hide and bond with its collagen fibres until the skin is rendered stable and imputrescible. The leather it yields is firm, warm in tone and alive to time: it darkens, softens and takes on character with use, which is why the method survives wherever leather is meant to be kept rather than replaced.

Bridle leather is a term of the saddlery craft rather than of any formal standard, and it names a vegetable tanned hide that has been curried and stuffed with fats and waxes until the leather itself is firm, dense and resistant to weather. The Italian tradition of the type is rooted in the country's centuries-old vegetable tanneries, above all those of Tuscany, and is distinguished by its handle: a smooth, close grain, a quiet lustre, and a body that softens with years of carrying without losing its strength.

English bridle leather descends directly from the harness and saddlery trades of England, where leather had to survive weather, sweat and the strain of working horses. Its historic home is the town of Walsall in the West Midlands, which grew from a market town into an international centre of saddle and bridle making; at the trade's peak around 1900 some ten thousand people there worked in leather. The type is vegetable tanned, then dressed and stuffed with greases and waxes on both sides, giving a firm, smooth-grained leather with a faint wax bloom and exceptional endurance.

The Tuscan leather district lies in the lower valley of the Arno, between Florence and Pisa, around the towns of Santa Croce sull'Arno, San Miniato and their neighbours. Vegetable tanning has been practised there for centuries and reaches its fullest modern expression in the district's tanneries, whose tradition has been protected since 1994 by a dedicated consortium that certifies genuine vegetable tanned leather produced wholly within the territory, to written production rules and independent inspection. The district is at once a place, a method and a guarantee, and its leathers carry all three.

Currying is the ancient craft of dressing tanned leather so that it is fit for hard service: cleaning, shaving to an even substance, stretching, and feeding the hide with oils, greases and waxes to the desired finish. It was for centuries a trade in its own right, distinct from tanning, and its London guild, the Worshipful Company of Curriers, dates from 1272. The word descends from corium, the Latin for the fibrous layer of the skin from which leather is made. Curried leather is stronger, suppler and far more resistant to weather than leather left undressed.

Hot stuffing is the currier's technique of charging leather with nourishment at temperature: hard tallows, greases and waxes are melted and worked into the warmed hide, most often by drumming, so that the blend penetrates deep among the fibres instead of resting on the surface. The practice defines the bridle and harness leathers, which carry within themselves a reserve of fats laid down at their making. A hot stuffed leather is heavier in the hand, quietly lustrous, markedly resistant to water, and slow to dry out across a lifetime of use.

Bloom is the fine, pale film that can rise on the surface of a heavily stuffed leather, and it is the visible sign of the riches within. Conservation science knows it as fatty bloom or spue: fats and free fatty acids, chiefly palmitic and stearic, migrate through the leather and crystallise on meeting the air, most readily when the temperature falls. It is not mould and it is not a fault; it is the leather's own wax come to the surface, and a soft cloth returns it whence it came, leaving the grain brighter for the polishing.

Patina is the surface character a leather earns through living: the slow deepening and enrichment of its colour and the low sheen that rises where it is handled and worn. In vegetable tanned leather it is the joint work of light, air, the oils of the hand and the gentle friction of use upon the natural tannins in the hide. Conservation practice treats an honest patina as part of an object's history rather than as damage, for it records the years without concealing them, and no two pieces ever earn the same one.

Full grain leather is leather that keeps its original grain surface entire: nothing buffed, snuffed or corrected away, so that the natural pore pattern, and any honest marks the animal earned in life, remain visible in the finished hide. The European terminology standard for the leather trade, EN 15987, reserves the term for leather bearing its complete, unaltered grain. Because the tightest fibres of the hide live at that surface, full grain is also the strongest expression of a leather. The words are used loosely in commerce; the standard's meaning is the one intended here.

Vachetta, from the Romance words for the cow, is an Italian style of vegetable tanned cattle leather, lightly greased and given little or no surface finishing, so that the material meets the world almost as the tannage left it. No formal standard defines the term; it is a name of the Italian craft, associated above all with Tuscany, for a naturally pale, supple leather that darkens readily in sunlight and hand, and earns patina faster than any other type. Its warm tone is the gift of the tannins themselves, not of added colour. Although classically left undyed, it is also produced in colours, dyed through in rotating drums after tanning. Milled vachetta is the same leather softened by tumbling in a drum, which relaxes the fibres and raises a fine, natural pebble in the grain.

Nubuck is grain leather whose outer surface has been very finely buffed on the grain side, raising a short, velvet nap of protein fibres. It is thereby the opposite of suede, which is napped on the flesh side or made from the split; nubuck keeps the strength of the grain layer beneath its soft face. It is warm to the touch, darkens for a moment under a fingertip or a drop of water, and returns to itself as it dries. Of the napped leathers it is the finer, the stronger and the more costly.

Palladium is a precious metal of the platinum group, silver-white with a cool grey cast, and a palladium finish is a plating of that metal over the body of a fitting. It is prized in fine hardware for a lustre quieter and warmer than chrome, for its good resistance to tarnish in ordinary atmospheres, and for being gentle to the skin. The plating takes and keeps a precise, even surface, which is why the finish belongs to buckles and fittings meant to be looked at closely for many years.

Self-lined is a maker's term rather than a standard's, and it describes a piece, most often a belt, lined with the very same leather as its face: two matched plies of one leather, or a single substantial leather finished on both sides, with no cheaper or foreign material hidden within. The construction is honest by nature, since the inside is of the same quality as the outside, and it ages evenly, both faces earning their patina together. Where a lining differs from the face, an honest description will say so.

Chrome tanning is the principal mineral tannage of the modern industry, developed in the nineteenth century and worked with basic chromium(III) sulphate. It converts a hide in a day rather than in weeks, and produces leather that is soft, light, uniform and receptive to bright dyes, which is why the majority of the world's leather is made this way. Its character is different in kind from vegetable tanned leather: it does not deepen and burnish into a patina in the same manner, because the tannage that stabilises it is mineral rather than botanical.

Tannins are natural plant polyphenols, large molecules of roughly five hundred to thirty thousand daltons, found in bark, wood, leaves, galls and fruits. Leather science divides them into two families: hydrolysable tannins, which are esters of gallic and related acids with sugars, drawn from sources such as chestnut, oak and tara; and condensed tannins, which are polymerised flavonoids, drawn from sources such as mimosa and quebracho. Both bind to the collagen of a hide and stabilise it against decay, and both lend leather the warm natural colour that deepens as it ages.

Top grain is a term of trade custom rather than of formal standard, and its meaning varies with the speaker. In careful usage it names a grain leather whose surface has been lightly buffed or corrected and then refinished, sitting a step below full grain; in loose usage, particularly in North America, it can mean no more than leather cut from the grain side of the hide. Because the words promise more than they define, they deserve scrutiny wherever they appear, and an honest description will always say what was actually done to the surface.

Spain's vegetable tanning tradition is among the oldest in Europe and once lent the language its very words for fine leather: the fame of Cordoba's hides in the Middle Ages gave English both cordovan and cordwainer, the old term for a shoemaker, and from about the fourteenth century Cordoba's leathers were vegetable tanned. Spanish full grain names leather from that continuing tradition with its grain surface left entire: slowly tanned with plant tannins, robust and warm of tone, and left to show the true face of the hide.

Milled leather is leather that has been softened by tumbling, dry, in a slowly rotating drum, a process the trade calls milling. The gentle, repeated falling relaxes the fibre structure and causes the leather's own natural grain to rise into a fine, even pebble, without any plate, press or embossing touching the surface. The pattern is therefore the hide's own, only awakened. Milled leathers are supple, quiet in lustre and forgiving in daily use, which suits them to pieces meant to be handled without ceremony.

Embossed leather carries a pattern pressed into its grain under heat and pressure, by an engraved plate or roller. The technique is ancient, and it may be used honestly to lend a regular texture or an ornament to the surface. Honesty is the whole question: trade terminology requires that an embossed grain be declared as such, and never passed off as the natural grain of another, rarer hide. A well-made embossed leather states what it is, keeps its pattern crisply for a lifetime, and hides nothing beneath it that needed hiding.

The grain is the outer face of the hide, the layer that lay just beneath the hair in life. Structurally it is the papillary layer of the skin, the densest and finest weave of fibres in the whole hide, and its surface carries the pore pattern and follicle mouths that are the fingerprint of real leather. Because its fibres are the tightest, the grain is also the hide's most durable face. In the language of the trade, everything concerning a leather's face, its markings, its finish, its truth, is a question of the grain.

The bend is a cut of the hide in the old cutting language of the heavy leather trades: the back of the hide with the shoulder trimmed away, which is to say the region over the animal's spine and hindquarters. It is the densest, firmest and most even leather the animal carries, with the straightest fibre and the least stretch, and for that reason it has always been the cut reserved for the work that must not fail: sole leather, harness, and the finest belts. To cut from the bend is to cut from the best of the hide.

The saddle stitch is the hand stitch of the saddlery trades: two needles on the two ends of a single thread, passed through the same awl-pierced hole in opposite directions, drawing the thread into a locked figure within the leather. Its virtue is independence: each stitch is secured in itself, so that if the thread is ever cut at one point the neighbouring stitches hold, where a machine lockstitch can run along the seam. It is slow, it cannot truly be imitated by machine, and it remains the strongest seam known to leatherwork.

A burnished edge is a cut edge of leather finished by hand: bevelled, moistened, and polished with friction, sometimes aided by water, wax or plant gums, until the exposed fibres lie down and seal into a smooth, dense, darkened line. Burnishing both protects the edge, closing it against moisture and wear, and declares the manner of the making, for it cannot be done in haste. On vegetable tanned leather the burnish deepens with the years, so that the edge, like the face, only improves by being carried.

Temper is the trade's word for the hand of a finished leather: its degree of firmness or softness, and the manner of its spring when flexed. Temper is set deliberately at the making, by the tannage chosen, the fats worked in, the substance to which the hide is shaved and the mechanical working it receives. A harness leather is tempered firm so that it holds its line; a glove leather is tempered soft so that it forgets it has one. Neither is the better; each is the right temper for its purpose.

Skiving is the paring of leather to a reduced thickness, most often at edges, folds and overlaps, with a skiving knife or machine. Its purpose is grace: a fold that closes without bulk, a seam that lies flat, a strap end that tapers cleanly. It is also a discipline of exactness, for a skive cut too deep weakens the leather and one cut too shallow defeats its purpose. In fine leatherwork the quality of the unseen skiving is one of the surest measures of the hand that made the piece.

Brass is an alloy of copper and zinc, and solid brass is that alloy through the entire body of a fitting, as distinct from a thin brass plating over a lesser metal. Because it contains no iron, solid brass cannot rust; left to itself it slowly mellows to its own soft patina, and it may be polished back to brightness at any time in its long life. A buckle cast or machined from solid brass can be refinished and repaired rather than discarded, which is why the heavy leather trades have trusted the metal for centuries.