The Eyewear Glossary

The vocabulary of fine eyewear, defined plainly. The terms an optician uses, in the order you are likely to meet them.

Acetate

Acetate is a plant-based material made from cotton cellulose, pressed into blocks and sheets, used for the finest eyewear frames. Unlike injected plastic, it is cut from a solid block, carries its colour all the way through, warms to the skin, and can be re-polished and re-adjusted for decades.

Mazzucchelli 1849

Mazzucchelli is the Italian acetate maker in Castiglione Olona, operating since 1849, widely regarded as the reference producer for eyewear acetate. Its sheets are seasoned for months so colour and grain stabilise before cutting. Every Berenford frame is cut from Mazzucchelli acetate.

Injection-moulded frames

Injection-moulded frames are made by forcing melted polymer into a mould, producing a frame body in under a minute. They are light and cheap to make, but the colour sits on the surface, the structure is hollow at the seams, and the material turns brittle and dull with sun and time.

Tumbling

Tumbling is the polishing stage in which cut acetate pieces spend days inside rotating wooden barrels filled with wood chips and pumice paste. The slow friction rounds the edges and produces the deep, even shine that distinguishes a handmade frame from a sprayed industrial finish.

Pantos

Pantos is a frame shape with rounded lenses and a flattened top line, slightly wider at the brow. It is the classic intellectual's shape of the 1930s and one of the most flattering forms for round and oval faces. The Berenford Gatsby is a pantos.

Aviator

The aviator is a teardrop-shaped frame originally developed for pilots, with a double bridge and generous lens coverage. In acetate rather than wire, it reads less military and more grand tourer.

Cat-eye

The cat-eye is a frame shape that sweeps upward at the outer corners, lifting the face. It flatters square jaws and strong features, and it is the silhouette cinema made famous in the 1950s and 1960s.

Keyhole bridge

A keyhole bridge is a bridge cut in the shape of an old keyhole, resting on the sides of the nose rather than the top. It distributes weight comfortably and gives a frame a vintage, hand-cut character.

Tortoise / Havana

Tortoise, also called havana, is the layered brown-amber pattern that imitates antique tortoiseshell. In fine acetate it is achieved by hand-layering translucent honey, amber and black, so the pattern has depth and never repeats exactly.

Riveted hinge

A riveted hinge is fixed to the frame with metal rivets that pass through the acetate, rather than glued or heat-staked. It is the most durable hinge construction and can be serviced by an optician. Visible rivets on the front of a frame are the traditional mark of this construction.

OBE

OBE is a German hinge maker in Pforzheim, founded in 1898, among the last in Europe to hand-rivet eyewear hinges. Berenford uses OBE hinges rated for over forty thousand open-close cycles, with a dedicated two-year guarantee.

Core wire

The core wire is the thin metal reinforcement running inside an acetate temple. It lets an optician adjust the fit precisely with gentle heat, and keeps the temple straight through years of use.

CR-39

CR-39 is an optical-grade polymer lens material, roughly half the weight of glass, with excellent optical clarity and good scratch resistance when coated. It is the standard for fine sunglasses lenses.

Mineral glass lenses

Mineral glass lenses offer the highest optical clarity and scratch resistance, at the cost of weight and shatter risk. Largely replaced by CR-39 and modern polymers in daily-wear sunglasses.

Polarised lenses

Polarised lenses contain a filter that blocks horizontally reflected light, cutting glare from water, snow and car bonnets. Useful at sea and on the road; occasionally inconvenient with some phone and dashboard screens.

Lens categories 0 to 4

Sunglass lenses are graded by darkness from category 0 (clear) to category 4 (very dark, not for driving). Most fine sunglasses, including Berenford, use category 2 or 3: dark enough for the Mediterranean, light enough to read a menu in the shade.

UV400

UV400 means the lens blocks ultraviolet light up to 400 nanometres, covering 100% of UVA and UVB. This is a property of the lens material, not of how dark the tint is. Every Berenford carries Zeiss lenses with full UVA and UVB protection.

Frame measurements (for example 49-21-145)

The three numbers engraved inside a temple are the lens width, the bridge width and the temple length, all in millimetres. Compare them with a frame that already fits you well and you can judge fit at a distance.

The Italian eyewear district

The province of Belluno in the Veneto is the historic centre of world eyewear manufacturing, home to the industry's largest groups and to the artisan workshops that serve the independent houses. Read how a frame is actually made there.

Limited edition numbering

A numbered limited edition means the maker commits to a fixed quantity, marks each piece with its number, and never reproduces the exact model. Berenford editions stop at one hundred pieces per model; the number travels with the frame on its certificate.

For the terms in practice, see the acetate story, the hinge story, and the Care Guide.