The frame material essentially determines the physiological compatibility and durability of a frame. Special attention must be given to allergies. Materials are classified in three main groups: metal, plastics and natural products.
Spectacle frames consist either of pure metal or of a combination of different alloys.
Stainless steel is widely used in the manufacture of frames due to its high tensile strength and corrosion resistance as well as its malleable and hypoallergenic properties. In addition, the material can be easily polished and coated in different colours, offering multiple finishing options. The frame parts are joined by brazing.
Titanium is a very popular material for creating frames. It offers excellent wearing comfort since it is the second-lightest metal on Earth after aluminium. Titanium is extremely robust, which makes it possible to manufacture ultra-thin spectacle frames. In addition, pure titanium is highly corrosion-resistant. Titanium-frames are nickel-free, which makes them the metal of choice for allergy sufferers. However, the material is rather expensive, since its extraction and processing is cost intensive.
Metal frames are coated with different alloys to improve the base material characteristics. Nickel silver (copper, nickel, zinc) and Monel (nickel, copper, small amounts of iron and manganese) are the most commonly used alloys. Both materials are easy to process and suitable for embossing, punching, milling, polishing and electroplating. Thanks to their superior elasticity, Monel and nickel silver frames can be individually adjusted to ensure the best fit for the wearer. The main drawback of both alloys is the relatively high nickel content. Spectacle wearers with known allergies should refrain from choosing frames made of these metal alloys.
Acetate frames are either injection moulded or cut out of a block of acetate plastic. Acetate is a very skin-friendly material. One problem is that, over time, a white residue forms on the frame due to the plasticizer migration. This residue can be removed again by polishing the frame. High temperatures are also disadvantageous since acetate can slightly deform in shape, while low temperatures increase the risk of the material breaking.
SPX is a polyamide processed by injection moulding. In addition to its superior tensile strength, SPX is also extremely lightweight, making it a premier material for sports frames and spectacles which have extremely fine rims or are rimless.
Optyl is an epoxy resin with high chemical resistance. Thanks to its extremely low density, it is suitable for the production of extremely lightweight spectacles that offer good wearing comfort. The hypoallergenic material contains no plasticizers and is thus not prone to brittleness. One of Optyl’s most significant characteristics is its memory effect. By heating it to 80°C and above, the material returns to its original shape. This is an important point to consider when adjusting the frame, since it must be held in the desired form until the material has cooled.
A wide variety of natural products are used for frame materials, including wood, horn, paper and tortoiseshell.
Natural materials are particularly suitable for people with sensitive skin and or allergies. In addition, natural products such as wood or paper are pleasant to wear because of their low weight. However, due to the material properties, frames made from natural materials are difficult to adjust, which is a major disadvantage. Manufacturers have responded to this problem by offering temples in different lengths, for example.