Cellulose acetate, from cotton fibre to frame sheet

Materials, 6 min read, August 2026

People say a frame is "acetate" the way they would say it is plastic. The two have almost nothing in common. Here is what is really inside the material we work with every day.

When a customer picks up a frame and asks what it is made of, the answer "acetate" does not get them very far. The word sounds technical, vaguely chemical, and it brings photographic film to mind rather than a pair of glasses. It is in fact the same product, and that kinship tells you most of what matters: cellulose acetate is a plant-based material, transformed, cast into sheets, then cut. Nothing to do with a material injected into a mould.

Where the material comes from

Cellulose is the main component of plant cell walls. The cellulose used for frames comes from short cotton fibres, the down left on the seed after ginning, and from wood pulp. That cellulose is treated with acetic acid, which produces a paste: cellulose acetate. A plasticiser is added to make it pliable under heat, along with pigments for colour.

The result is neither a petrochemical plastic nor a raw natural material. It is a transformed, plant-based material with one unusual property: it stays workable under heat for its entire life. That property, not just the way it looks, is why opticians prefer it.

From paste to sheet

The coloured paste is then shaped. The historic manufacturers in Italy, China and Japan stack, press and slice blocks to create patterns. This is how tortoiseshell, marbled and gradient effects are born. A tortoiseshell pattern is not printed, it is built: layers of differently coloured paste are stacked, compressed, then cut across. The pattern therefore runs through the full thickness of the sheet.

These sheets are usually a few millimetres thick and a little under one square metre. Every sheet reference has its own number and its own pattern depth, and two sheets carrying the same number are never one hundred per cent identical. That is why two of our frames in the same colourway always show a slightly different drawing.

From sheet to frame

The frame is cut out of the sheet, then hollowed, milled, drilled for the hinges and finally polished. Polishing happens in stages, from the most abrasive to the gentlest, often in barrels filled with wood chips and polishing paste, over several days. That long polishing is what gives the shine its depth, the depth you never find on an injected frame that came out of its mould already glossy.

The method also explains something wearers notice quickly: an acetate frame can be readjusted. Heated for a few seconds, it bends, holds its new shape as it cools, and can be reworked as many times as needed, years later.

"A sheet is not a stock of material, it is a stock of patterns. We never reorder a sheet expecting to find exactly the same one."

Acetate versus injected plastic

Injected plastic is a thermoplastic melted and poured into a mould already shaped like the finished frame. It is fast, consistent and inexpensive. Its limits show up in use: the colour often sits on the surface, or is flat and without depth, the material copes poorly with repeated heat, and heat adjustment is limited, sometimes impossible. An injected temple that has loosened gets replaced, not recovered.

A simple check in store: look at the edge of the frame where the lens sits. On acetate, the pattern carries on through the thickness. On an injected frame, that edge is often plain, in a colour that does not quite match the front.

How acetate ages

Treated well, acetate keeps its shine for a very long time. Two things damage it: extreme heat and solvents. A frame left on a dashboard in the sun can warp. Cleaning with alcohol or acetone attacks the polish and leaves a whitish haze. Lukewarm water, a drop of neutral soap and a microfibre dry are all you need.

Over the years, a heavily worn frame can lose a little of its lustre, especially where it touches the skin. That is reversible: a repolish at an equipped optician restores the original finish, something no injected frame allows.

What this changes when you choose

Acetate is not automatically better. It is heavier than titanium, thicker than fine metal, and it costs more to produce. It wins on three fronts: colour, with a depth no other material matches, adjustability, which lets a frame follow your face for years, and repairability.

If you are hesitating between two frames, take the time to ask for the exact material, and look at the edge. The answer is written inside it.

See the material up close: our Materials page details the sheets we work with and where they come from.