The chemical process used to stabilise an animal hide's collagen structure, converting it from a perishable material into durable leather. The two principal tannage methods relevant to Hermès production are vegetable tannage and chrome tannage. Tannage determines the leather's reactivity to moisture, UV light, and skin oils — and therefore its patina behaviour, care requirements, and long-term surface character. It is the most fundamental property description of any Hermès leather.

A tannage method using plant-derived tannin molecules — polyphenolic compounds from oak bark, quebracho, mimosa — to cross-link and stabilise the hide's collagen fibril proteins. Vegetable tannins remain chemically active within the fibril network after tanning, making the leather hygroscopic (moisture-attracting) and highly reactive to UV light. This reactivity drives the dramatic patina development of vegetable-tanned leathers — most notably Barenia Faubourg in the current Hermès range. Vegetable tannage takes weeks; chrome tannage takes hours. The slower process produces deeper, more organic chemistry in the fibril structure.

A tannage method using chromium salt compounds that form stable, irreversible chemical cross-links with the collagen fibril proteins. Chrome tannage is the method used for Togo, Clemence, Epsom, Swift, Box Calf, and the chevre leathers. The chromium cross-links are inert after tanning — they do not react with moisture or UV light in the way vegetable tannins do. Chrome-tanned leathers are significantly more moisture-resistant, develop more restrained patina, and require less intensive care than vegetable-tanned alternatives. The trade-off is that the dramatic, fibril-deep patina of vegetable-tanned leather is simply not achievable with chrome tannage.

A post-tanning finishing process in which a leather hide is passed through high-pressure rollers that compress the grain surface to a high gloss — the defining process of Box Calf leather. The box-pressing compresses the upper fibril layer into a rigid, high-density matrix that produces the mirror-bright surface characteristic of Box Calf. The same compression principle — applied with an engraved rather than smooth roller — is used to create Epsom's cross-hatch embossed grain. Both processes produce their characteristic surfaces by exploiting the fibril compression response to mechanical pressure.

The individual collagen fibre bundles that make up the three-dimensional matrix of a leather hide. Fibrils are the fundamental structural unit of leather — their density, orientation, and degree of cross-linking (set by tannage) determine virtually every property of the finished leather: temper, weight, scratch resistance, oil absorption, and patina behaviour. Tighter, more densely packed fibrils (as in Chevre Mysore or compressed Epsom) produce stiffer, lighter, more scratch-resistant leather. Looser, more widely spaced fibrils (as in Clemence's belly-section hide) produce softer, heavier leather with greater oil absorption capacity.

The surface pattern of a leather hide — whether natural (produced by the animal's own skin texture) or processed (produced by embossing, drum-tumbling, or other finishing techniques). Natural grain reflects the fibril tip pattern at the hide's outer surface and varies by animal species, age, and body section. Processed grain is mechanically imposed onto the natural surface: drum-tumbling creates Togo's and Clemence's pebbled grain; embossing rollers create Epsom's cross-hatch. Grain type determines scratch visibility, patina oil-absorption pathways, surface reflectivity, and the visual character of the finished leather.

The stiffness or suppleness of a finished leather — the degree to which it resists deformation under applied force. Temper is set primarily by tannage and finishing, and it determines how a bag holds its shape under load over years of carry. Epsom has the firmest temper of standard Hermès leathers (box-pressing + chrome tannage). Clemence has the most supple temper (belly-section hide + chrome tannage without embossing). Togo occupies a middle position — self-supporting under moderate load but supple in hand. Vegetable-tanned Barenia has a supple temper that softens slightly over time as the fibril network responds to use.

The surface treatment applied to a leather after tanning — including any topcoat, pigment layer, glazing process, or protective treatment that sits above the natural grain surface. Finish type determines the leather's sheen level (matte, semi-matte, glazed), its scratch visibility, its patina capacity, and its moisture resistance. Epsom's compressed cross-hatch grain is a finish in itself — the embossing process is the final surface treatment. Swift has a thin semi-matte topcoat finish. Box Calf's mirror gloss is achieved through the box-pressing process rather than an applied coating. Barenia's natural finish is minimal — the leather's surface is largely uncoated, which is why it is so reactive to oils and UV.

The surface change that develops in leather over time through use, skin oil absorption, UV exposure, and — in vegetable-tanned leathers — tannin migration and oxidation. Patina is a quality signal, not a damage indicator: it represents the leather's authentic response to use and indicates genuine ownership history. In chrome-tanned leathers, patina manifests primarily as tonal deepening at contact zones and surface sheen development through friction. In vegetable-tanned leathers, patina is a deeper, fibril-level transformation driven by tannin chemistry. The desirability of patina varies by leather type: broadly considered positive in Togo and Barenia, neutral in Epsom, and read as wear rather than character in Box Calf.

The natural surface film that forms on vegetable-tanned leathers as tannin molecules migrate toward the grain surface through the fibril network and oxidise in contact with air and light. Exclusive to vegetable-tanned leathers — most notably Barenia Faubourg in the current Hermès range. The pellicule is not a product applied to the surface; it is generated by the leather's own chemistry. It is responsible for the characteristic depth and luminosity of aged Barenia — the sense that the leather is lit from within. It develops most visibly in the first twelve to eighteen months of active carry and continues building throughout the leather's life. Chrome-tanned leathers do not form a pellicule.

Describes leather with a soft, flexible temper that moves with the hand and body rather than resisting it. Suppleness is produced by a combination of looser fibril architecture (as in Clemence's belly-section origin) and the absence of rigid embossing processes (as in Togo versus Epsom). Supple leathers develop a more tactilely warm, organic character over time as the fibril network responds to carry and conditioning. The trade-off for suppleness is generally reduced shape retention under sustained load — supple leathers require more active storage discipline to maintain their factory geometry over years of carry.

The two-needle hand-stitching technique used on all authentic Hermès bags, in which a single length of waxed linen thread is drawn simultaneously through each pre-awled hole from both sides by two separate needles. The threads cross inside each hole, creating a stitch that is structurally independent — one broken stitch does not cause adjacent stitches to unravel, unlike machine lock-stitch. Saddle stitch runs at a consistent ~45-degree diagonal to the seam line on authentic pieces, at 4–5 stitches per centimetre on body seams and higher density at structural stress zones. It is a definitive authentication marker and the structural foundation of Hermès bag durability.

The impressed letter, symbol, or combination identifying the individual craftsperson who assembled the bag — present on every authentic Hermès piece since 1984. Applied using a heated metal die pressed into the interior leather surface. Distinguished from the date letter stamp (production year indicator) and the foil stamp ("HERMÈS PARIS MADE IN FRANCE" exterior text). The blind stamp's location, impression depth, and fibril response at the impression boundary are all forensic authentication markers. Its location has shifted in 2026 production pieces relative to prior years — a current authentication advantage for secondary market buyers.