5.03 metal frames

Question 1

important note about metal frames

Answer 1

• very few ‘metal’ frames are actually purely metal
• metal alloys is dead (mixture of several metals)
• these addition add different beneficial properties (e.g increased corrosion resistance or reduced susceptibility to metal fatigue)

Question 2

metal frame material requirements

Answer 2

• same characteristics needed as jewellery (good appearance/ nor ration to skin or cosmetics)
• gold (24k too soft and costly, use 9k)
• silver (soft, tarnishes in air)

Question 3

gold filled/ rolled gold

Answer 3

• solid cylinder of base material
• surrounded by hollow cylinder of carat gold
• higher carat = less risk of allergy, but softer
• fused together , stretched and pressed to required oprifile
• rare
• finished wire cut to correct shapes and soldered together
• final gold plating over soldering for optimum appearance
• get different shades of gold via different alloys
• copper is red, zinc is white

Question 4

what is a electroplating bath?

Answer 4

• used to achieve a coating of gold
• multi stage process to build up layers
• adhesion, protection

Question 5

how thick is a gold layer in a finished frame?

Answer 5

• 10-20 microns
• can be thinner in some areas if stretched a lot
• carries marking to show gold content

Question 6

gold plated

Answer 6

• make frame components out of base metal
• solder into completed shape and tumble polish
• gold plate entire frame in electrolytic bath
• can make some designs which are not possible with gold gilled (perforated)
• rare in general practice but some specialist stockists around

Question 7

characteristics of electroplated frames

Answer 7

• thinner layer of gold on finished frame (2 microns)
• cheap alt to gold filled
• uses higher carat gold
• as thinner layer not as susceptible to damage
• less risk of allergy
• even thickness without very thin areas

Question 8

what is used for the base metal?

Answer 8

• several different alloys used, sometimes combined in same frame
• alloys of copper, tin, zinc, nickel
• diff alloys used in different areas of frame
• depends on characteristics needed (e.g. rigidity at bridge or flexibility at sides)
• used to reinforce sides on plastic frames

Question 9

nickel silver

Answer 9

• base metal used a lot
• 14% nickel, NO SILVER
• nickel: low content, can cause allergic reactions
• dull silver colour
• not pretty enough to be used alone
• can sell nickel free frames

Question 10

silver frames

Answer 10

• very rare
• NOT ACTUALLY SILVER, just in colour
• base metal electroplated with rhodium or chromium
• chromium extremely corrosion resistant: reacts with air to give layer of chromium oxide
• matt black frames can be created by coating of black chromium oxide

Question 11

aluminium

Answer 11

• lightweight
• cold to touch
• anodizing converts the surface to aluminium oxide
• oxide can be coloured, matt, shiny
• oxide is resistant to corrosoion, rigid, resistant to bending, risk of cracking oxide coating
• can’t be soldered as joined pinned to front and sides

Question 12

stainless steel

Answer 12

• alloy of steel and chromium
• resistant to corrosion and tarnishing (used in surgical instruments)
• no plastic end covers on side but can have them
• rigid and hard to work with unless very fine sides and rims

Question 13

titanium

Answer 13

• hypoallergenic
• 50% light than conventional metal
• can’t be adjusted if very pure or soldered so all alloys
• corrosion resistant
• abrasion resistant
• looks gold or silver
• costly produciton
• can’t use normal soldering method
• if soldered it means barely any titanium present

Question 14

memory metal or shape memory metal

Answer 14

• patients think theyre unbreakable but aren’t
• alloys of titanium 50% and nickel 40%
• lightweight but potential allergy issue
• parts can be glued together to avoid “losing memory” but soldering process
• hard to adjust so use heating
• frame made from lots of materials

Question 15

coloured coatings

Answer 15

• used on top of base metal to colour whole frame
• or on gold filled or plated
• electrostatic coating of plastic powder granules
• melted to give even thickness coating
• dipped into dye bath
• clear nail varnish makes cheap alt in case of allaergu