The Material World
A global guide to some of the materials that make up today's frames
By Erinn Morgan

As the base for the whole eyewear package, frame materials hold a significant role. The material used in the manufacture of the frame helps determine whether eyewear will be light or heavy, flexible or stiff, and unique or simple.

The beginnings of eyewear date back to sometime between 1268 and 1289 in Italy when lenses were made from quartz and were usually set into a front piece of bone, metal, or leather that was pinched onto the nose. It wasn't until nearly 400 years later that opticians figured out that rigid sidepieces resting on top of the ears might come in handy. Thus, the frame as we know it today was born. The earliest versions were made of wood, horn, leather, or bone. Later on, materials included brass, tortoiseshell, baleen (from the upper jaws of baleen whales), steel, silver, and gold.

Today, frame materials range from the basic (i.e., metal alloys like Monel™ and stainless steel) to the high-tech (i.e., copper beryllium and co-injected silicone). There is just about something for every customer—from the person looking for light weight to the sports participant in need of increased flexibility and fit.

Certainly, different materials will appeal to various people. While titanium might be more interesting to tech-savvy consumers, plastics may better suit those with a fashion bent. However, your knowledge of materials can go way beyond who might simply be interested in them. Dig beneath the surface and you will see that each frame material has an interesting story to tell.

	Gold, wood, and horn are luxurious frame options. Shown above: Horn style CB 14 from Gold & Wood

ALUMINUM

The Basics: Pure aluminum is soft enough to carve. Mix it with small amounts of alloys, however, and it can provide the strength of steel with only half the weight. Because it can be "sculpted," the softer properties of aluminum break down the creative barriers present with many other strong materials. It is also one that is readily available—it is the most abundant metal in the earth's crust.

The Pros: In addition to its aesthetic merits, this material is also strong, lightweight. The fact that it can be recycled also makes it increasingly desirable.

The Cons: This material can get rigid, especially in lower temperatures. Thus, integrating elements like flex hinges into an aluminum frame can be difficult.

Other Uses: Ancient Greeks and Romans used alum as an astringent. Today, it is used in everything from kitchen utensils and cans to bicycle frames and foil.

BERYLLIUM

The Basics: Discovered in France in 1797, this high-performance material is six times stronger than steel and more than 30 percent lighter than aluminum.

Beryllium has gained a small place in the manufacture of eyewear because of its strength and light weight. It is also used as a component in the alloy Trilaston™, used in the manufacture of some memory metal eyewear.

The Pros: In addition to its strength and light weight, beryllium can withstand high temperatures.

The Cons: A small number of people are allergic to beryllium.

Other Uses: An element found in rocks, coal, and oil, beryllium is used for electronic connectors in cell phones, airbag sensors, and fire extinguishers. It is also used for X-ray windows and as an alloy for high-performance aircraft, missiles, and spacecraft.

	Titanium is strong and attractive. Shown: Titanium eyewear style T545 from Seiko Optical Products

HIGH-TECH ALLOYS

The Basics: The list of unique alloys used in the eyewear industry continues to grow, and each new material offers something special on the technology front—from extra comfort to increased flexibility.

Some manufacturers are using a new co-injection of silicone and nylon for a more streamlined, lightweight fit. Another popular usage of material alloys in frame manufacture is bendable, memory metals.

The Pros: Some of these titanium- based alloys are 10 times more flexible than steel and 25 percent lighter that conventional metals.

LUXURY MATERIALS

The Basics: Designers on the high end of the market are using exclusive materials such as gold, platinum, horn, and specialty woods to craft their frames.

Precious metals such as gold and platinum have benefits such as hypoallergenic qualities, durability, strength, and status. Horn is typically a by-product of domestic buffalos farmed for meat—no animal is taken specifically for its horns. It is one of the most environmentally sound frame materials because there is no metal or plastic production involved.

On the wood front, frame designers are looking to ebony, bubinga, and rosewood as staples for unique styles. Wood frames are cut from block or, better yet, from laminated sheets put together for desired patterns or designs.

The Cons: These luxurious materials must be cleaned or polished to keep them looking their best. Some customers may also look at the high price tag as a deterrent.

	Plastics have many style options. Shown: Etro style SE9186 by Viva International Group

MAGNESIUM

The Basics: This material is the eighth-most abundant metal element on earth. Lighter than both titanium and aluminum, magnesium is either extracted from the ocean or recovered from minerals such as dolomite or magnetite. Because of its unique properties and high cost, it has been used in the high-end frame market.

The Pros: This super-lightweight material is strong and hypo-allergenic.

The Cons: Magnesium costs almost 50 percent more than aluminum or steel.

Other Uses: Discovered in 1775, magnesium is used to build race cars, missiles, and aircraft.

MONEL™

The Basics: Discovered in 1901 by Robert Crooks Stanley, who worked for the International Nickel Company (named after the president of the company, Ambrose Monell), Monel is a nickel alloy containing 68 percent nickel, 30 percent copper, and two percent iron.

This ductile material, which is the most commonly used frame material today, is often used for components that require sturdiness and rigidity, such as temples and bridges.

The Pros: This alloy is said to be stronger than steel, malleable, resistant to corrosion, highly resistant to alkalis, and fairly inexpensive. It can also be welded, brazed, and soldered—properties ideal for the manufacture of frames.

The Cons: Monel is so sturdy that it can be difficult to shape into frame fronts. If used for this eyewear component, it can be difficult to work with to fit lenses.

In addition, surface discoloration can occur from exposure to atmospheric conditions. Pitting can occur if exposed to salt water. Metals, such as aluminum, zinc, and iron will corrode when in contact with Monel and exposed to severe weather.

Other Uses: The material was used as a sheet roofing membrane in the early 1900s, as well as for grocery coolers, countertops, and sinks. Monel castings were also popular architectural details.

	High-tech alloys are durable. Shown here: Style Ketyum Golf II by Rudy Project

NICKEL SILVER

The Basics: Another popular material for frames today, nickel silver consists of 62 percent copper, 22 percent zinc, and 18 percent nickel. It is similar to Monel in that it is sturdy and well-suited for frame components like temples and bridges. It is also called German silver or alpaca.

The Pros: This frame material is extensively used because of its hardness, toughness, light weight and resistance to corrosion.

The Cons: Because of its rigidity, it is not suitable for frame fronts and is difficult to fit lenses into. Frames made of nickel silver will often utilize a different material for the frame front. This material is also not very bendable or malleable.

Other Uses: Discovered in the early 19th century by German industrial chemist E. A. Geitner, nickel silver is used today in tableware, hospital and restaurant equipment, plumbing fixtures, and heating coils because of its high electrical resistance.

PLASTIC

The Basics: Easily colored, laminated, patterned, or even layered with fabrics, this material is one of the more creative and workable options. There are two commonly used plastic frame materials—cellulose acetate and cellulose propionate.

Cellulose acetate, better known as zyl, is the most commonly used plastic frame material—it is made from cotton seed fibers and wood flakes. Cellulose propionate is used specifically for injection molded frames, where the plastic resin is melted, forced into a mold, and cooled so it can hold the frame shape. Frames made of cellulose acetate are generally cut from sheets of the block acetate. While this plastic can also be injection molded, most industry experts agree that the sheet method is more foolproof.

Sheet stock is created by one of four methods: Block (colors are hand-laid and pressed with heat and pressure); extrusion (colored resins are melted and fed into a dye that regulates the flow of color to create patterns); laminate (extruded or block products are laminated in layers to create a desired effect); and ceblox (plastic is placed in a mold and turned into a sheet by compression molding).

The Pros: Plastic frames are lightweight and hold their shape well, so they can be made fairly thin. On the fashion front, plastics are popular because of the many colors and patterns possible.

The Cons: Because they hold their shape well, plastic frames actually have less room for expansion. Thus, some may experience difficulty when inserting lenses into the frames. In addition, injection molding can present problems such as microscopic bumps, dust, or dirt within the mold, which can appear as a defect on the frame.

STAINLESS STEEL

The Basics: This material is actually an alloy of iron and carbon steel with chromium and other elements. The addition of at least 10 percent chromium makes this alloy less prone to stain or rust, a factor that results in a long life compared to that of traditional steel. Because of its durability, light weight, and sleek appearance, stainless steel has long been a choice of eyewear designers.

The Pros: Stainless steel is non-corrosive, durable, strong, lightweight, and hypoallergenic. It can also be easily shaped into ultra-thin eyewear styles and has flexibility, which adds to the wearer's comfort. It can also be more easily colored than titanium and is less expensive that its lightweight counterpart.

The Cons: Stainless is still not as lightweight, heat-resistant or flexible as titanium.

Other Uses: Structures made of stainless steel can last well over 100 years. Since this material is also 100 percent recyclable, it can be melted down and reincarnated to live out another life of utility.

TITANIUM

The Basics: This high-strength, lightweight material was used to construct the A-12 Blackbird spy-plane in the 1950s and the Mercury, Gemini, and Apollo space capsules.

Today, titanium is commonly used in everything from hubcaps to eyewear. Because titanium ranks seventh in abundance among industry elements in the earth's crust, it is easily accessible. Its combination of attributes—the lightweight, high-strength, durable, and non-corrosive nature of titanium—make it appealing.

This material has picked up speed in the eyewear industry as a lightweight option that lends itself to unique designs and colorations. It also comes in handy for today's oversized styles that benefit from lighter weight.

The Pros: Titanium is very strong, lightweight, hypo-allergenic, and corrosion-resistant. For many applications, it is a preferred substance because it is strong as steel but much lighter.

The Cons: This material is more costly than most commonly used materials. In addition, both pure titanium and titanium alloys are used in the manufacture of eyewear. Today, many companies clearly mark what frames are made of—be sure you get the grade of titanium for which you have paid.

Other Uses: First discovered in 1791, titanium is often used for joint replacement parts, including hip ball and sockets. It has excellent resistance to seawater and is used for propeller shafts, rigging, and other exposed parts of ships. Titanium paint is an excellent reflector of infrared radiation, and is extensively used in solar observatories where heat often causes poor viewing conditions.