Spectacle Frame Materials

Key features of tortoiseshell spectacle frames

• Hawksbill turtle origin → licence required (endangered species)

• Brilliant polish

• Lightweight + hard

• Repairable over steam

• No side reinforcements

• Metal‑to‑metal joints

• Handmade → no adjustment required

Buffalo Horn

• Warm natural colours

• Lightweight

• Hypo‑allergenic

• Expands with heat but doesn’t warp

• Hard material but flakes easily → needs monthly moisturising

• Becomes brittle when dried out

• Metal‑to‑metal joints

Key features of wood spectacle frames

• Beech/boxwood/cedar/bamboo/lime commonly used

• Hard + lightweight

• Size changes with humidity

• Some woods can be poisonous

• Handmade only → cannot be adjusted

Key features of plastic spectacle‑frame materials

• Ease of production

• Economical

• Corrosion‑resistant

• Non‑flammable (mostly)

• Durable

• Rigid

• Adjustable

Types + requirement of synthetic spectacle‑frame plastics

• Cellulose derivatives (acetate, nitrate, propionate)

• Acrylics

• Nylons

• Epoxy resins

• **Must be thermoplastic materials

Key features of cellulose nitrate spectacle‑frame material

• Cotton linters + nitric acid

• Camphor plasticiser

• Highly inflammable → burns rapidly

• Softening temp: 65°

• Flashpoint: 70°

• Smells of camphor when filed

• Discontinued due to fire risk

Key features of cellulose acetate spectacle‑frame material

• Acetic acid + cotton linters

• Impact resistant

• Poor warp resistance

• Can be dyed/laminated

• **Softens at 57° but doesn’t burn

• Attacked by skin acids

• Reinforced sides

Key features of cellulose propionate spectacle‑frame material

• Cellulose flakes + propionic acid

• Colour via dyeing / transfer printing / lacquering

• Strong + good elasticity

• **Softens at 67°

• Injection‑moulded

Acrylic

• Polymethyl methacrylate (PMMA)

• Stable, rigid, lightweight

• Hard but brittle → adjusts only at very high temperatures

• Mushroom‑pinned joints

• Non‑reinforced sides

• Dermally inert

Key features of Optyl spectacle‑frame material

• Epoxy resin with no plasticiser → “memory effect”

• Vacuum‑cast production

• Hard + lightweight

• Softening temperature: 80°

• Resistant to burning

• Hypoallergenic

• Short side reinforcements

Key features of SPX spectacle‑frame material

• Super polyamide — nylon‑based

• Ultra‑light + extremely strong

• Made only by Silhouette — famously worn by the Queen

• Injection‑moulded

• Highly elastic + impact resistant

• **Softens at 95°

• Hypoallergenic

Key features of nylon spectacle‑frame material

• Children’s / safety / sunglasses — common applications

• High break‑resistance

• High memory

• Injection‑moulded

• Difficult to adjust unless reinforced

• Extra‑deep groove required

Polycarbonate

• Used for one‑piece plano safety goggles

• Very soft

• Virtually unbreakable

• Non‑reinforced sides

• Difficult to adjust

Key features of carbon‑fibre spectacle‑frame material

• 20% carbon + 80% nylon

• Injection‑moulded

• Naturally grey → coated or lacquered for colour

• Extremely strong + lightweight

• Heat‑resistant / high melting point

• Sprung metal sides (usually)

• Early models had closing blocks

  • Closing blocks = old hinge‑stabilising design

Key features of rolled‑gold spectacle frames

• Good corrosion resistance

• Maintains appearance

• Low risk of skin reactions

• **Base metal: nickel silver

• Quality stamped on all frames

Key features of gold‑plated spectacle frames

• Uniform gold coating

• Variable coating quality

• Thickness varies from frame to frame

• Can cause skin problems

• Organic protective layer added to protect the frame

Key features of nickel‑silver spectacle‑frame material

• Contains no silver

• Copper + nickel + zinc alloy

• Easy to manufacture

• Can be soldered → easy to repair

• Can cause skin allergies

• **Usually electro‑plated with pure nickel after manufacture

Key features of aluminium spectacle‑frame material

• Extremely lightweight

• Requires anodising

• Cannot be soldered

• Riveted assembly

• Cold to the touch

• Difficult to adjust

• Used mainly for sides & trims

Types + key features of titanium spectacle‑frame material

• Pure titanium

• Clad‑in titanium — similar to rolled gold

• Partial titanium

• Resistant to corrosion

• Melting point: 1673 °C

• Difficult to solder

Stainless steel

 Very rigid
 resistant to corrosion
 lightweight
 easily adjusted
 discolours when heated
 originally used for rimless mounts

Memory metals

• Titanium–nickel alloy

• 8× more flexible than steel

• Returns to original shape

• Fatigue‑resistant → will not kink

• Resists breakage

• Difficult to adjust

• Used for bridges & sides only