Metal
Standard Monel metal (nickel alloy)
Gold Filled.
Stainless Steel.
Titanium.
Aluminium Alloys. (not routinely used)
(a) STANDARD MONEL METAL.
Most metal frames are made from a nickel alloy of varying proportions depending on whether that part of the frame has to be stiff or flexible. Nickel is a potentially allergic substance and so is plated with a precious metal such as gold and ideally lacquered to further protect the precious metal against the corrosive effect of the uric acid in the perspiration. Some nickel frames have a very thick ' rolled gold' type of covering. This is almost a thing of the past and such a frame is called "Gold Filled". This is very expensive as the gold layer is much thicker.
(b)STAINLESS STEEL.
This is very 'springy' light, non-corrodeable, giving usually a very fine frame. Ideal for people who perspire profusely, live in hot countries, play a lot of energetic sports or come in contact with salt water. Comes in various degrees of purity. Stainless steel is hypoallergenic.
(c) TITANIUM.
Like stainless comes in different degrees of purity which affect it's properties and corrosion resistance. The titanium wire of Air Titanium Frames is very springy and fine, whereas the titanium used in many Rodenstock and Menrad frames is quite stiff. Titanium frames are a premium product costing more than stainless steel. N.B.-Titanium frames if they are broken cannot be re-soldered back together acceptably, despite some frame repair firms to the contary! Titanium is hypoallergenic.
(1) Acetate.
In the past all plastic frames were cut out of a block of acetate plastic. This produces a solid frame with a colour that passes from one side of the plastic to the other.
(2) Propinate.
These frames are injection moulded, used for larger production runs usually. This material is used for budget mass-produced frames as well as some fine high quality frames from suppliers such as Rodenstock and Luxottica.
A propinate frame keeps it's shape at warmer temperates better than acetate. This has an advantage that it can keep it's shape better once fitted but it is less malleable under heat.
Propinate frames are usually cast moulded as a clear frame and then sprayed or dyed with a surface colour afterwards. As a result it cannot have the deeper, solid colours of an acetate frame. Propinate frames are cold-glazed for best results. They do not change shape on heating however.
(3) SPX/Polyamide. (Silhouette/ Micheal Selcott)
These above materials which usually have the marking "SPX", or a "PA" on their sides and "Cold Glaze" or "Use no heat" on the new frame's dummy lenses, should be treated with great caution. You must not use the frame heater.
Polyamide/ SPX is a very fine lightweight material used by Michael Selcott, Rodenstock and Silhouette. It's comes in a variety of finishes. The simple answer with frames from manufacturers is to look for the identifying marks on the sides.
T material is difficult to adjust especially when old, as it gets very brittle especially in cold weather. It also seems to shrink when it ages, sometimes makes removing lenses without breaking the frame very difficult. Because of this, old polyamide / SPX frames should not be reglazed ideally at all, but if you have to, the frame could break and this is done at ones own risk.
If you see a SPX Silhouette frame with a reverse bevel which holds the lens into the frame by gripping a "Supra-Type" groove around the lens periphery, then definitely do not reglaze as this design has not been made for a decade, so will break almost definitely.
(4) Optyl.
Like propinate, Optyl is a cast-moulded plastic,this time from the EPOXY family (like Araldite). It is a thermosetting plastic. It stays in a particular shape until it gets to a high temperature (about 83 degrees C - quite hot!) Above this temperature it will soften and can be re-shaped into a new adjustment shape.
It must be restrained to this new shape while it cools down. It will then keep this shape indefinately till it exceeds 83 degrees C once more. It is thus quite tricky to adjust but very useful type of material in that when it is going to retain it's adjusted shape eventually forever. Do not worry if you lose control of Optyl adjustment, if it has taken on a totally incorrect shape, it can warmed up to it's original "out of factory"shape, so that you can start again!agh! It is also hypo-alleric so ideal for patients with a nickel sensitivity.
If in doubt Optyl frames are made by the Optyl Group of companies so if the frame has the following brands it is likely to be made of Optyl - Christian Dior, Viennaline, Terri Brogan, Dunhill, Palmo Picasso, then it should be adjusted with care.
Because Optyl has a u-shaped bevel it has to be glazed a bit tighter than an acetate (like propinate.)
(5) Carbon fibre.
Made of plastic reinforced with carbon fibres (like fishing rods),this makes it light weight and strong. Usually comes with metal sides
Beware of the coating on a carbon fibre frame coming off with people who perspire a lot. The expensive ones (mainly Slazenger) do not do this so much,but the only safe option is the Black Burley by "Hoi" ,steer patients tactfully away from carbon fibre especially with the coloured Hoi frames that is.
(6) Glass fibre.
Popular mainly with Benneton. Cold glaze. Very difficult to adjust if they are not perfect as standard
(7) Rubber and Nylon.
These are speciallity frames usually for sport or babies. Can be a nightmare to glaze.
