It requires that on the basis of these standards, each EU member state put its own nickel legislation into force. However, the test methods were not considered to be wholly suitable for application to optical frames and sunglasses, in view of the fact that they wouid actually cause abrasive damage to the frames. Certottica, the Italian institute that certifies optical products, suggested a more suitable testing procedure, which was approved by other international standards organizations, including the ISO, earlier this year. The new test devised by Certottica is expected to replace the current specifications by January 2001. With technological change have come major changes to the structure, color and mechanical performance of the frame.
Frames have fewer and fewer stress points and are getting lighter and lighter.
It is now common to see a number of different metal materials combined in one construction to achieve an integral design that provides outstanding performance. The eye wire, for example, might be produced in a strong, durable material such as Monel while the temples and bridge, which need to fit on and around the face comfortably, are produced in more flexible materials. A variety of techniques are used to produce different colored metals. Titanium, for example, changes color when subjected to an electrolytic process. The final color of the frame depends on the length of time it is submerged in an electrolytic solution.