Spectacle frame materials This data is presented as a resource that can be used for students and supervisors alike. It is intended to be a growing thing that will be modified and updated as new information and images become available and new materials are introduced. If anyone would like to contribute or correct anything that is presented here please feel free to email me at darylnewsome2@gmail.com
Acrylics. Polymethyl Methacrylate. (Perspex.) Not very common now. Acrylic resin, very stable, made from acetone, sodium cyanide, methanol and sulphuric acid. Production method usually by routing. It is commonly used in nylon supras. The colours are achieved by laminating onto pale base shades. The sides have no reinforcement and mushroom pinning is used to secure the joints. It is a rigid, lightweight, hard but very brittle and has a high, lasting polish. The adjustment temperature is 68C, but care should be taken because it is easily broken below this temperature. However, excessive heat will cause blistering.
Aluminium. Aluminium is the most abundant metal in the earths crust, accounting for approx 8% of the weight of the earths solid surface. It is non-magnetic and non-sparking. Aluminium is too reactive chemically to occur in nature as a free metal. Instead, it is found combined in over 270 different minerals. Aluminium is lightweight, strong, very rigid, stain and tarnish resistant. It can be anodised to produce a range of colours. Aluminium cannot be soldered or brazed and as a result the parts are assembled by riveting or screwing. It is also extremely difficult to adjust. Very cold to the touch when first picked up, usually finished with a matt surface.
Berylium Copper. Beryllium copper, also known as copper beryllium, BeCu or beryllium bronze, is a metal alloy of copper and 0.5 to 3% beryllium, and sometimes with other alloying elements. Beryllium Copper combines high strength with non-magnetic and non-sparking qualities. It has excellent metalworking, forming and machining qualities. It has many specialized applications in tools for hazardous environments, musical instruments, precision measurement devices, bullets, and aerospace. Beryllium-containing alloys create an inhalation hazard during manufacturing due to their toxic properties. It is shiny, coloured silvery white and very strong. Berylium copper is flexible and malleable but too hard to be worked without annealing (heating to high temperatures and rapidly cooling) Very suitable for very thin sides or small parts.
Bronze. Contains at least 60% copper together with 4 to 25% tin, zinc and lead. It is yellow or brown in colour, with a variable resistance to corrosion it can be low but also it can be good due to variation in the alloys contents. It is used as the base for the rolled gold material.
Carbon Fibre. Made from nylon 80% and carbon fibre 20%. Production is by injection moulding. The material is naturally grey but has limited colours available, the limitation being due to the technique of coating and lacquering. Carbon fibre frames are rigid, lightweight, very strong ( though it can “split� on the rim if dropped) and shrink resistant. Heating has no effect other than possibly to soften the surface resulting in finger prints being left on the frame. As a result metal sides, with acetate end tips, are use to facilitate adjustability. Early frames had closing blocks for lens retention (similar to metal frames). Later models are cold glazed, but require very accurate glazing if the lens is to be sprung in.
Cellulose acetate
Made from cotton linters and acetic acid, and plasticiser. Production methods. In sheets, acetate transfer moulding, extrusion moulding, and injection moulding. Produced as a frame by routing. The colours achieved by lamination or dye moulding. The joints may be pinned or heat inserted. Normally polished by the barrel polishing method.
Side have “shot” reinforcement. This means the side is made out of a routed peice of acetate, placed in a metal mould which heats the side up to its plasticity temperature and then the side is placed in a cold metal mould, the side cools from the outside inwards and as it does so a reinforcement is pushed into the soft plastic center, this metal reinforcement is guided down the center of the side by the hardened exterior. The material is fairly soft so has a high resistance to impact but a poor resistance to warping. Adjustment temperature 57C, it is non-flammable but excessive heat will cause the material to "bubble"! This occurs when the interior of the plastic starts to boil and the resultant gas formed produces small vacuole within the substance of the plastic. As cellulose acetate ages the plasticiser tends to “dry out” and the material becomes more brittle and requires higher adjustment temperatures and, needless to say, more care in adjustment. This in very old frames can cause the dry surface to loose its polish and appear "powdery", it will however take a new polish with jewlers rouge and a polishing mop.
Cellulose Nitrate ( Banned in the U.K. because it is highly inflammable and burns very rapidly an extreme hazard. Its softening temperature is 65C but its flash point is 70C need one say more!) Made from cotton linters and nitric acid with a camphor elasticise. When cellulose nitrate is warmed or filed this camphor smell becomes very evident, so if in doubt test first! It becomes bright yellow with age. Production method is by routing, because of the low flash point it cannot be moulded. The joints are pinned and the sides reinforced. The colours are normally produced by shaving veneers. The material is tough, has dimensional stability and a good surface lustre. Though banned in the U.K. the material is still used in the Third World so it important that we know about cellulose nitrate and very specifically its hazards.
Cellulose Propionate Made from cellulose flakes and propionic acid, acetic acid, plasticiser and stabiliser. Production method is by injection moulding. The joints are injection moulded and the sides are reinforced. The colours are obtained dyeing over a pale base, transfer printing and then lacquered (resulting in a hard, high gloss finish) The material is reasonably strong and temperature resistant. It has good elasticity and is resistant to ageing. It is also lighter than acetate. The adjustment temperature is 67C, but excessive heat causes shrinkage! Advantages: Relatively lower plasticiser migration than Cellulose Acetate or Cellulose Acetate Butyrate. Stiffer than Cellulose Acetate or Cellulose Acetate Butyrate. Transparent and glossy with better low temperature impact properties Cellulose Acetate or Cellulose Acetate Butyrate. Disadvantages: Lower weathering resistance than Cellulose Acetateor Cellulose Acetate Butyrate. More expensive than Cellulose Acetate or Cellulose Acetate Butyrate. Attacked by acids & alkalis and swollen by chlorinated and aromatic hydrocarbons, alcohols and ketones
Ceroid Production method is by routing. The adjustment temperature is 100-110C. Ceroid is very lightweight, strong and flexible, together with a high impact resistance and excellent dimensional stability. The colour is contained within the material offering superior colour retention when compared to acetates. It can be barrel polished or lacquered.
Epoxy Resin
Optyl. Epoxy resin which requires no plasticiser. The production method is by compression moulding. It is a thermosetting material. Optyl is coloured by dyeing and then lacquered resulting in a very high gloss finish. It is very lightweight, hypoallergenic, it is resistant to burning and cannot be shrunk. The adjustment temperature is 80-120C (though it is virtually impossible to damage it by heating even to very high temperatures.) Care should be taken when adjusting as Optyl is a brittle material that will break easily if the adjustment temperatures are not achieved, the material must be malleable before attempting to adjust it, cool in water. As with all moulded frames Optyl styles are designed to be produced with built-in “base curve.� Therefore they do not need to be bumped and bowed into shape. A very interesting feature regarding Optyl and heat is the it has a memory. That is to say it can be heated to the malleable state, then heavily deformed (even fitted into a bottle) allowed to cool and harden when re-heated it will revert back to its original shape. Is that not magic! Also when identifying Optyl look for the characteristic short side reinforcement.
Gold Filled (Rolled Gold) Produced by bonding a skin of carat gold onto a base metal (usually nickel silver or bronze) The gold filled block is then cold hammered before being rolled into a suitable size/gauge for drawing into a viable frame making wire. Gold Filled material is sold to manufacturers already profile, i.e. it is quality stamped as a fraction (1/10 12ct) or by parts per 1000, the 1/10 fraction refers to the total gold content of the frame by wieght. The thickness of gold on a gold filled frame is 50 to 100 000 times thicker than a gold plated frame! The material has a good resistance to corrosion. It maintains its appearance and is fairly hypoallergenic provided it does not constantly touch the skin. It is easily adjusted, by pliers or fingers. It is easily repaired by soldering, though sometimes discolouration may result.
Gold Plating. Cheaper, but generally inferior, alternative to Gold Filled. Produced by multi-layer coatings using a thin layer of platinum to seal the base metal (such as monel), then covered by a gold electroplate, the layers are uniform and achieved by electrolysis (electro-plating). These frames are very often finished with an anti-corrosion layer in the form of a clear laquer.
Gold Wash. A base metal is covered with a very thin deposit of gold either by electro or chemical deposition. There is no platinum seal performed on the base metal so when the thin layer is worn through the skin is immediately exposed to the substrate. Wears off very quickly, exposing the base metal which may result in allergies. Mainly used in the manufacture of cheaper sunglasses.
Gold. (pure) You will not see this in an exam. It is a material available only to the very rich. price at 10th Feb 2016 is ÂŁ816 per ounce. Gold is the most malleable and ductile of all metals in the world. A single gram can be beaten into a sheet 1 meter square ! An ounce can be beaten into a sheet 300 square feet! Gold leaf can be beaten so thin it becomes translucent, although the light transmitted through it appears greenis blue because gold strongly reflects yellow and red light. Generally speaking “solidâ€? gold is not only too expensive for the vast majority it is really too soft for satisfactory frame manufacture. Pure gold is 24 carat designated and, if produced within the U.K. will be suitably Hall Marked on each frame component.. 18 carat gold has 18 parts pure gold and 6 parts alloy. Again this will be correctly Hall Marked. 12 carat has 12 parts pure gold and 12 parts alloy. Once again it will be suitably Hall Marked. Gold is measured in Troy ounces and grams. Since the 1880's South Africa has been the main supplier of gold, Johannesburg being formed as a result of the witwatersrand gold rush! However in 2007 for the first time ever China overtook South Africa as the biggest source of global Gold, other gold mining countries are America, Peru, Chile and Argentina, the main global consumer of gold is India, accounting for 25% of the worlds gold sales!
Horn Extremely rare, almost non existent. Usually Buffalo horn. A very high quality material, being natural it is hypoallergenic. Natural horn colours, think of some of the drinking vessel you may have seen in places such as Spain or some of the Viking and mediaeval. It is a material that offers a wonderfully high polish, beautiful natural colours and an exquisite feel. It is very difficult to adjust. Can be obtained from managed sources.
Monel. Usually made from 29% copper 68% nickel, approximately 1.25% iron and approximately 1.25% manganese. The nickel is there to offer corrosion resistance, the copper for flexibility and the manganese to increase resistance to tarnishing. Other elements such as aluminium, carbon and silicon are often added. It has a dull white appearance. Because of its contents it can result in allergies. Monel is a trademark of Special Metals Corporation for a series of nickel alloys, primarily composed of nikel (up to 67%) and copper, with some iron and other trace elements. Monel was created by David H. Browne, chief metallurgist for International Nickel Co. Monel alloy 400 is binary alloy of the same proportions of nickel and copper as is found naturally in the nickel ore from the Sudbury (Ontario) mines. Monel was named for company president Ambrose Monell, and patented in 1906. One L was dropped, because family names were not allowed as trademarks at that time. One of the more famous uses of monel is that it was used to make "dog tags" for the armed forces.
Neodymium Iron Boron For years the use of magnets has been constrained by the size of a ferrous magnet needed to create a useful magnet. Neodymium iron boron magnets have revolutionised this industry and the spin off can be seen in other industries such as optics! The new generation of magnetic clip on sunspecs which attach to certain frames, such as Flexon magnetic range and convertibles owe their existance to these small powerful magnets. An equivelent Ferrous magnet would have to be four or five times its size and would not be discrete enough to use on spectacle frames. Another example of the use of these light weight strong magnets are the tiny remote control helicopters which dominate our shopping malls and large toy stores! Such powerful electric motors could not be made light enough without Neodymium Iron Boron magnet! So it's not all progress then! Neodymium Iron Boron magnets are a type of rare earth alloy that typically has two atoms of Neodymium (Nd), 14 atoms of Iron (Fe), and one atom of Boron (B) as its primary elements, hence their chemical composition Nd2Fe14B, which is commonly abbreviated as NdFeB. There are other elements that are used to increase the coercivity, to gain lower oxidation characteristics, and to obtain other desirable characteristics. These elements are used to "dope" the alloy and are generally found in small quantities (<10% by weight). A word of caution: Do NOT use Neodymium Iron Boron magnets under the following conditions: o o o o
o o
In an acidic, alkaline, or organic solvent (unless you are going to hermetically seal the magnet inside a can) In water or oil (unless hermetically sealed, or you are prepared to accept a limited life) In an electrically conductive liquid, such as electrolyte containing water In a hydrogen-containing atmosphere, especially at elevated temperatures.Hydrogenation, a process where the Hydrogen molecule will react with the NdFeB, will occur, causing the magnet to rapidly deteriorate Environments containing corrosive gasses, such as Cl, NH3, Nox, etc. In the path of radioactive rays
Nickel Silver Contains no silver! It is an alloy comprised of 60% copper (providing flexibility) 18% nickel (corrosion resistance) 20% zinc and manganese. In inferior alloys the nickel content may fall to less than 5% with a corresponding increase in the zinc and manganese. Nickel silver is cheap and easy to manufacture, with the parts being easily soldered together. Solder repairs are also easy. It retains its shape well. The draw back is that many patients are allergic this material, so the frames often feature xylol covering to the eyerims and sides.
Nylons Nylon Originally created by Wallace Carrothers in 1935 at the Du pont research facility, it is an abreviation of New York London reflecting both countries involvement in its development. Developed as a replacement for silk, early uses include toothbrush bristles, ladies stockings and military parachutes. Used mainly for childrens frames, safety eyewear and sunglasses. Production method is by injection moulding. The production is only commercially viable when high quantities of single items are produced. Nylon has a high resistance to breakage with a high degree of memory and as a result it has poor adjustment properties. The sides are more easily adjusted if reinforced, but very commonly metal sides are used to make adjustment easy, these are normally screwed on. Colours limited, usually black, brown or grey. It is cold glazed and features extra deep grooving to facilitate adequate lens retention. As a material it is very difficult to recycle and often finishes slowly degrading in landfill!
Polycarbonate Very, very soft and as a result virtually unbreakable. Polycarbonate frames have non reinforced sides. They are mainly used in safety eyewear.
Rhodium A rare member of the platinum family. Rhodium was discovered in 1803 by William Hyde Wollaston. It is found in platinum- or nickel ores together with the other members of the platinum group of metals. Rhodium is mostly used as a catalys in the three-way catalytic converter. Rhodium is inert against corrosion and most aggressive chemicals, and because of that and its rarity, rhodium is usually alloyed with platinum or Palladium and applied in high-temperature and corrosion-resistive coatings. White Gold is often plated with a thin rhodium layer to improve the optical impression. It is one of the rarest precious metals and, with a price of about ÂŁ55, 000.00 per Kilo in 2010, is the most expensive member of that class. It offers a highly reflective effect after polishing and is used as a mechanical plating for base metals. It can however corrode and is therefore protected by an intermediate layer. Having said this it is used as a colour coating and tarnish protection (obviously with the intermediate layer) on white rolled gold, white gold plated frames and trim decorations etc
Ruthenium This is a member of the platinum family and as such is corrosion resistant. The colour varies from blue-white to silver grey and is often used to provide a gun metal colour effect.
Shape Memory Alloys. Contains 50-80% copper, 2-8% aluminium and zinc and titanium. The material is fatigue resistant and has a super-elastic effect (It has 8x more spring than stainless steel. It is usually used on bridge and side components with eyewires using more trasditional metals such as monel. Sides that require shortening to the point where the adjustment needs to be performed on the elastic area of the wire can be annealed to eliminate the springy characteristic. Annealing is acheived by heating the area one wishes to bend until it is red hot with a flame and then submersing the hot metal in cold water.
SPX Peculiar to Silhouette, though other manufactures are now using similar materials. SPX is classed as a super-polyamide – the SP (the X designates Silhouette’s secret ingredient). It is a nylon derivative. It is produced by injection moulding. SPX is an excellent frame material. It has a plethora of desirable features. SPX being lightweight, strong, mouldable, highly elastic, impact resistant. It is dermatologically inert (hypoallergenic,) it is easy to adjust and colour (offering a wide range of colours and patterns). It is resistant to solvents, cosmetics, alkalines and oils. It is twice as resistant to abrasion as acetate or propionate, together with a lacquered finish that offers a wonderfully high degree of polish. The adjustment temperature is 95C but excessive heat will cause shrinkage. The frames are cold glazed (due to the risk of shrinkage as mentioned above) they also featured in the past “in-line” glazing, which neccesitated edging the lens with a flat edge and a supra groove. The sides are reinforced and as a result the shrinkage is not a problem when sides are adjusted. The joints are injection moulded.
Stainless Steel. Stainless steel is an alloy of iron together with 18% chromium and 8% nickel. It is assembled by welding ( it cannot be soldered in the normal way) Stainless steel is corrosion resistant, tough and flexible (more flexible than ordinary steel) Often used for brow bars of rimless mounts and combination frames. As a material it may be coated with silver, gold or even coloured plastics, making identification difficult. Stainless steel is 100% recyclable. An average stainless steel object is composed of about 60% recycled material of which â&#x2030;&#x2C6;40% originates from end-of-life products and â&#x2030;&#x2C6;60% comes from manufacturing processes.
Titanium Titanium is the Worldâ&#x20AC;&#x2122;s fourth most abundant metal element, so it is not rare nor is it any more difficult to mine than other metal ores. There is pure Titanium. There is Titan B (90% purity with manganese) this is more elastic and harder than pure titanium. Also Titan C, the most expensive: this is galvanised with twice the usual thickness of gold, palladium etc. Production of Titanium frames, however, is very expensive. The unique manufacturing process involves cutting, pressing and laser soldering (this is done in an Oxygen free atmosphere, usually an inert gas such as Argon. The frames are coloured by galvanic cladding or ion plating. Titanium cannot be soldered in the normal fashion. Though expensive the cost is justified in that Titanium is an excellent frame material. It is very lightweight with a specific gravity of 4.5gms/cm, that is half the weight of nickel silver. It is very flexible and therefore strong, its elasticity being 20% higher than nickel silver. Titanium has a very high degree of corrosion and abrasion resistance with a surface hardness 3x that of rolled gold material. It is also hypoallergenic, especially in its pure form. The side ends of Titanium frames are specially alloyed to allow for ease of adjustment (the side will also have an acetate or similar cover end tip) Because of this be very careful when shortening the sides of Titanium frames, they will be virtually impossible to bend! A metallic element, symbol Ti in the periodic table, titanium is recognized for its high strength-to-weight ratio. It is a strong metal with low density that is quite ductile (especially in an oxygen-free environment) lustrous, and metallic-white in colour and has fairly low electrical and thermal conductivity. Commercial (99.2% pure) grades of titanium have ultimate tensile strength of about 63,000 psi, equal to that of common, low-grade steel alloys, but are 45% lighter. Titanium is 60% more dense than aluminium, but more than twice as strong as the most commonly used 6061-T6 aluminium alloy. However, titanium loses strength when heated above 430 °C (806 °F). The most noted chemical property of titanium is its excellent resistance to corrosion; it is almost as resistant as platinum, capable of withstanding attack by dilute sulphuric
acid and hydrochloric acid as well as chlorine gas, chloride solutions, and most organic acids. However, it is slow to react with water and air, because it forms an inert and protective oxide coating that protects it from further reaction when it first forms, this protective layer is only 1–2 nm thick but continues to slowly grow; reaching a thickness of 25 nm in four years. When exposed to elevated temperatures in air, however, it readily reacts with oxygen. This occurs at 1,200 °C (2,190 °F) in air, and at 610 °C (1,130 °F) in pure oxygen, forming titanium dioxide. As a result, the metal cannot be melted in open air since it burns before the melting point is reached. Melting is only possible in an inert atmosphere or in a vacuum. Titanium is also one of the few elements that burns in pure nitrogen gas, reacting at 800 °C (1,470 °F) to form titanium nitride, which causes embrittlement.
Turtleshell. (Real shell or Tortoiseshell). A high quality product. The material you are more likely to come across. It is obtained mainly from the endangered Hawksbill Turtle (now a protected species) You can imagined the huge sigh of relief from all the tortoises in the world when they realised it wasnâ&#x20AC;&#x2122;t them we were after! Made in sheets by layering and forging plates together under pressure and steam. If you look very carefully you can sometimes see the striation/lines evident where each layer has been bonded. Splicing again using steam and pressure techniques can also repair the material. It is however a very highly skilled craft and it is virtually impossible to find a shell frame maker now. Real shell is hypoallergenic. The material will take a very high, lasting polish and the colour may vary from a dark blended mottling with greenish patches (these are the back plates) to the very expensive, though not the most attractive, almost clear amber (made from the belly plates) The most attractive however was the red shell (taken from the lower back plates) The frames usually have metal to metal joint and the sides are not reinforced. The adjustment temperature is 75C and I suppose the nearest modern material to real shell with regard to adjustment techniques is Optyl. Though protected real shell is obtainable under licence from managed sources.
Yak Horn Yak Horn is used to produce jewellery, combs, pipes and ornaments in China. Recently it has started to appear as sides on spectacle frames imported from China. Often sourced from the Qinghai-tibet pleateau. It is a relatively inexpensive horn compared to buffalo and deer. It can be considered as an organic material to have the same properties as "horn." Very difficult to adjust and quite easy to break. It offers a very highly polished finish. It is a material favoured by importers such a Nick Turnbull.