Sunglasses frame materials: acetate, injected plastic, TR90, nylon and metal, compared honestly

The frame material decides how much a pair weighs, how it flexes, how it survives being sat on, whether an optician can adjust it, and how it ages. Acetate is the premium plastic: cut from sheet, polished by hand, with colour all the way through, adjustable with heat, and heavier and dearer than the rest. Injected plastic is moulded from pellets: lighter, cheaper, colour on the surface, limited adjustment. TR90 and nylon are the flexible plastics that sport frames use. Metal adjusts and lasts but weighs more and corrodes near salt. None is best. Each suits a different pair and a different owner.

Acetate

Cellulose acetate is a plant-derived plastic made in sheets. A frame is cut from the sheet, tumbled and polished, and the colour, tortoiseshell, crystal, laminated stripes, runs all the way through the material. That is why an acetate frame can be polished back to new and why the colours look deep rather than painted.

Acetate softens with gentle heat, which is how an optician adjusts it: widen the front, curve the arms, reshape the bridge. It is also heavier than injected plastic and much dearer, because the cutting and polishing take work.

Choose it for: a frame you will keep for years and want adjusted to fit. Trade: weight and price.

Injected plastic

Most affordable frames, including ours, are injection-moulded: molten plastic forced into a mould, cooled, popped out. The material is usually a polycarbonate blend or a similar engineering plastic. It is light, cheap to make, and consistent.

The trades: colour is applied to the surface or mixed into a single-colour batch, so it cannot match acetate's depth; the frame cannot be heat-adjusted the way acetate can, and forcing it can crack it; and cheap moulded frames can be brittle in cold or after years of UV.

Choose it for: light, affordable everyday sunglasses. Trade: limited adjustment, less depth of finish.

Our T01 is injected plastic with a perforated texture moulded into the front and arms. It is light, it has no adjustable parts, and it should not be heated to reshape. Every product page states the material as the frame maker lists it.

TR90 and nylon

TR90 is a trade name for a nylon-based thermoplastic; other sport frames use similar nylon blends. The defining property is flex: these frames bend a long way and spring back, and they are very hard to snap. They are also light and hold their shape through heat and cold better than ordinary injected plastic.

The trades: almost no adjustment, because the material springs back; a matte or rubbery finish that some people dislike; and, on cheap versions, the same surface-deep colour as any moulded plastic.

Choose it for: sport, children, anything that gets sat on. Trade: cannot be adjusted.

Metal

Stainless steel, titanium, aluminium and alloys. Metal frames are thin, so the lens takes the eye rather than the frame; they have adjustable nose pads and arms, so an optician can fit them precisely; and they last.

The trades: weight, especially in steel with glass lenses; nose pads that need cleaning and replacing; corrosion in salt air unless titanium or well-plated; and metal conducts cold, which matters in winter. Titanium is the exception on weight and corrosion, and it is priced accordingly.

Choose it for: a precise fit, a thin profile, longevity. Trade: weight, salt, price for titanium.

Side by side

Fit and material

Material sets what can be done about fit. A frame that presses at the temples can be widened if it is acetate or metal and not if it is injected plastic or nylon; our headache post covers that pressure. A frame that slides can have its pads reset if it is metal, or stick-on pads added if it is plastic; our slipping post and low bridge post cover both. Getting the width right at purchase matters most for the materials that cannot be adjusted afterwards, which is why our measurements post exists.

How to tell what you have

• Acetate: heavy for its size, colour visible in the cut edge, a faint smell of vinegar when warmed.
• Injected plastic: light, a seam line where the mould halves met, colour uniform.
• TR90 / nylon: bends alarmingly and springs back, matte finish.
• Metal: obvious, with pad arms at the bridge.

Frequently asked questions