Frame Materials

Question 1

Cellulose Acetate (plastic)

Answer 1

• inexpensive
• fairly light - density 1.27
• always has reinforced sides
• adjust at 57 degrees celcius
• needs reinforcement or can warp and become soft
• joints can be heat inserted, pinned or screwed
• can react with skin - can be metal joints so can lead to rash
• can be cut from a block or poured semi molten into a mould - this is stronger as the molecules arent cut
• solid colouring - thicker frames, bolder colours, can laminate with clear sheet for transparent colours
• lacquered and polished for shine
• discolours with age - can react with skin - white deposits and materials become rough to touch
• to recognise - colour all through and where sides meet frame front you can see it has been cut - rough edge

Question 2

Optyl (plastic)

Answer 2

• epoxy resin registered by safilo
• side only reinforced for first 12mm - not really required, more decoration
• can be laminated or dyed then polished
• joints are injection moulded
• hypoallergenic
• 30% lighter than cellulose acetate
• memory plastic - softens at 88 degrees - need to hold adjustment in place until it has cooled or itll return to its original shape

Question 3

SPX (plastic)

Answer 3

• nylon based super-polyamide made by silhouette - always marked SPX
• sides always reinforced
• joints are injection moulded
• can be dyed or lacquered
• adjust at 95 degrees C - SHRINKS if overheated, cold glaze only
• impact resistant
• flexible
• lightweight

Question 4

Cellulose Propionate (plastic)

Answer 4

• often marked cp
• sides always reinforced
• joints injection moulded around hinges
• can be dyed or lacquered after cutting, so where side meet front is smooth
• adjust at 67-70 -SHRINKS if overheated so cold glaze
• good stability but hard to adjust
• lightweight
• hypoallergenic

Question 5

Acrylic/PMMA (plastic)

Answer 5

• sides unreinforced, often metal
• joints are pinned
• -frame front usually laminated, sides dyed - bright colours used
• v brittle, so only used for supra styles (often upswept)
• needs to be heated to a high point before any adjustment therefore hard to adjust

Question 6

Carbon fibre (plastic)

Answer 6

• nylon composite (20% carbon, 80% nylon) often with metal sides
• joints always pinned
• lacquered
• cant be heated - so cant adjust and diff to glaze
• v inflexible
• strong
• light

Question 7

Cellulose Nitrate (plastic)

Answer 7

• blocks of nitrate sliced into sheets
• sides always reinforced
• joints always pinned
• laminated or crystal (yellows quickly though)
• highly flammable - DO NOT ADJUST
• smells of camphor if scratched (if in doubt test in an inconspicuous place)
• joints can rust and turn green
• brittle - can crack with age

Question 8

Gold (metal)

Answer 8

gold filled = fraction of gold content marked in parts per 1000 marked on the bridge
rolled gold - has a base metal (nickel silver/ bronze) core. Gold content encircled and marked on the bridge or the sides
-keeps colour well
- soft
-resistant to corrosion
- hypoallergenic unless underlying base metal exposed

Question 9

Nickel Silver (metal)

Answer 9

• most common metal for frames - inexpensive
• contains copper, nickel, zinc and manganese
• parts assembled by soldering
• colour can be electroplated or lacquered (can wear off)
• easily adjusted
• flexible
• some corrosion resistance
• nickel can react to skin

Question 10

Nickel Titanium (metal)

Answer 10

• memory metal
• 50% titanium
• only used for bridge and sides (not joints)
• 23% lighter than silver nitrate

Question 11

Stainless Steel (metal)

Answer 11

• assembled by welding
• strong and flexible
• coloured by electroplating
• hypoallergenic
• corrosion resistance
• often no end tips
• rigid and flexible
• can be welded

Question 12

Aluminium

Answer 12

• less widely used
• expensive
• lightweight
• rigid so hard to adjust and repair (can only be laser soldered)
• hypoallergenic
• shiny and can be coloured by anodising
• parts for frame all cut from one piece of material

Question 13

Titanium (metal)

Answer 13

• mined as an ore - expensive. Then cut, pressed and laser soldered
• colour galvanised or ion plated
• hard to repair (needs computer controlled laser soldering at 1280 degrees)
• hypoallergenic
• flexible
• usually marked
• corrosion resistance

Question 14

Tortoise Shell (metal)

Answer 14

• now illegal, but seen occasionally
• natural material made from Hawksbill turtles
• stable
• adjusted using steam
• if broken - can be spliced using another piece of shell and steam
• joints always pinned
• sides reinforced
• metal joints