Plastic
If you want the colors of the rainbow, then zyl (zylonite, or cellulose
acetate) is your material. Zyl is a very cost-effective and creative option
for eyewear and is extremely lightweight. Particularly popular right now
are laminated zyl frames that have layered colors.
Some manufacturers are also using propionate — a nylon-based plastic
that is hypoallergenic. It's lightweight and has a different look and
feel than other plastics.
Eyeglasses made of nylon were first introduced in the late 1940s. Because of brittleness and other problems, eyeglass manufacturers switched to blended nylon (polyamides, co-polyamides and gliamides). Today's blended nylon frames are both strong and lightweight.
Plastic frames do have some drawbacks. They are easier to break than metal frames, they will burn (but are not easily ignited), and aging and exposure to sunlight slightly decrease their strength but do not affect color.
Metal
Monel - a mixture of any of a broad range of metals -
is the most widely used material in the manufacture of eyeglass frames.
It is malleable and corrosion-resistant — especially if the right
kind of plating, such as palladium or other nickel-free options, is used.
Frame manufacturers are coming out with more and more titanium styles
these days; titanium is a silver-gray metal that's lightweight, durable,
strong and corrosion-resistant. It has been used for everything from the
Gemini and Apollo space capsules to medical implants such as heart valves.
Titanium eyewear can be produced in a variety of colors for a clean, modern
look with a hint of color. Not all frames are 100 percent titanium. Some
frames are made from an alloy that is a combination of titanium and other
metals, such as nickel or copper.
Beryllium, a steel-gray metal, is experiencing increased popularity as a lower-cost alternative to titanium eyewear. It resists corrosion and tarnish, making it an excellent choice for wearers who have high skin acidity or spend a good amount of time in or around salt water. It's also lightweight, very strong, very flexible (making it easy for an optician to adjust your glasses) and available in a wide range of colors.
Stainless steel frames are another alternative to titanium. Qualities of stainless steel frames include light weight, low toxicity and strength; many stainless steel frames are also nickel-free and thus hypoallergenic. Stainless steel is readily available and reasonably priced. It's an alloy of steel and chromium; it may also contain another element. Most stainless steels contain anywhere from 10 to 30 percent chromium, which imparts an excellent resistance to corrosion, abrasion and heat.
Flexon is a titanium-based alloy. This unique and popular material, which is proprietary to the eyeglass manufacturer Marchon, is called a "memory metal" because it can go back to its original shape if damaged. Frames made of Flexon come back into shape even after twisting, bending and crushing. Flexon frames are lightweight, hypoallergenic and corrosion-resistant.
Aluminum, frames made from aluminum are lightweight and highly corrosion-resistant. Aluminum is used primarily by high-end eyewear designers because of the unique look it creates. Aluminum is not only the world's most abundant, but also the most widely used, nonferrous material. Pure aluminum is actually soft and weak, but commercial aluminum with small amounts of silicon and iron is hard and strong.
