GUNTER Flashcards
NATURAL FRAME MATERIALS
- “real shell”
- horn (buffalo)
- wood
WOOD FRAMES
can split + warp
difficult to glaze - doesn’t stretch
absorbs water + sweat if coating damaged
can be adjusted with great difficult - dry heat can crack it
more stable if laminated
many woods are toxic or carcinogenic
WHICH NATURAL FRAME MATERIAL CAN NO LONGER BE OBTAINED NEW + WHY?
“real shell”
it’s the carapace (shell) of the hawksbill turtle + it’s illegal to kill them anywhere in world - protected
THERMOPLASTIC
goes soft when heated + hard when cooled
THERMOSETTING
becomes hard or solid when heat is applied + remains that way on being re-cooled
change is not reversible
ACRYLATES/ ACRYLICS
thermoplastic - high softening temperature
easily broken
usually supras
claimed hypoallergenic
never yellows with age
no reinforcing wire inside
CELLULOSE ACETATE
thermoplastic
light/ strong/ cheap/ hard ISH
good colour range
can be made in layers to give shell effect
pads sometimes stuck on with acetone
almost always have reinforcing wire in side
half joint attached to front by heat/ ultrasonic insertion + attached to side by soldering
hypoallergenic in pure form but never used in this form
WHAT TEMPERATURE DOES ACETATE SOFTEN AT?
56 degrees
WHY IS CELLULOSE NITRATE BANNED IN UK?
it’s flammability
ignition point + softening point are very close
CELLULOSE NITRATE
made by routing (cut from sheet with spinning tool)
half joints always riveted to front + sides
if clear, turns yellow + crystallises with age
CELLULOSE PROPIONATE
very common thermoplastic
light/ strong/ cheap/ hard ISH
half joints always hear unsettled or screw-on lug on front
usually polyurethane lacquer coated
almost always surface coloured
EPOXY RESINS
thermosetting plastic
liquid monomers react in mould
claimed to be hypoallergenic
polyurethane coated - protects, reduces allergenic potential + facilitate surface dyeing
light material - little metal in most
epoxies used to coat metal frames
POLYAMIDES
large group of polymers
safety/ sports/ toddler frames
sunglasses
low density, can be strong
shrink when heated (usually
glazed cold)
usually made by moulding
can be coated with lacquer
POLYCARBONATE
best known as a lens material
strong + light
often used for sunglasses + side shields on safety specs
very high softening temp
surface dissolves in acetone if not lacquered
no side reinforcement
SILICONE RUBBERS
nose pads, bridges + side tips on metal frames
non-adjustable
soft, flexible material
usually have acetate cores
extremely stable + retain their elastic properties from -50 to 200 degrees
LIQUID/ GEL SILICONES
pads on metal frames
in a silicone rubber envelope
FLEXIBLE POLY-VINYL CHLORIDE (F-PVC)
majority of pads on metal frames
not sticky to touch
semi-soft
often have acetate or metal cores
COMPOSITES
fine, strong fibres set in another plastic
cracks have to go round the fibres before frame breaks
CARBON FIBRE
best known composite
mostly nylon
fibre just adds strength
always grey/black
surface often has coloured lacquer
most have closing block to secure lens
KEVLAR
long chain polyaramides
composite
softens in a frame heater
ROUTING
process in which sheets of material have the excess cut away to form the frame with a “routing” machine
WHICH PLASTIC ARE MOST OF PADS ON METAL FRAMES MADE FROM?
silicone rubber
f-PVC + liquid/gel silicone
WHAT IS IN A METAL FRAME TYPICAL STRUCTURE?
base metal, plating, organic coating + plastics/silicone fittings
WORK HARDENING
aligns crystals in metals - makes harder + springier
can also make them more brittle
makes metal harder through plastic deformation
