Frame materials come and go. Since we always follow the Golden Rule of Optical which is, “To get something, you have to give up something.” That just sort of makes sense.

There are two kinds of frame materials: metals and plastics.

Metals have four general types:

1. Monel, or basic nickel-based metal frames. These are inexpensive and make up the bulk of all low and mid-range metal frames made today. If a frame is metal and not flexible or not marked ‘stainless steel’ or ‘titanium,’ chances are excellent it is a Monel-based frame.

Advantages of Monel-based frames:

• Easy to adjust
• Hold adjustments well
• Very strong
• Relatively light in weight
• Can have a wide range of colors and plating like bright gold and bright silver
• Economical
• Can be repaired by solder

Disadvantages of Monel -based frames:

• Outermost plating (the layer that touches the skin) can wear off, which can cause skin allergies or reaction to nickel in Monel metal
• Prone to breaking after repeated bending
• Once plating is worn away, metal may erode quickly and create abrasive areas and sharp edges
• Monel is the heaviest of metal frame materials in use

2. Stainless steel is used in many mid-range to high-end frames. If a frame is metal and looks as if it is made of a material just a little thicker than a paper clip, then chances are excellent that it is made from stainless steel. Stainless steel is also made in the same shape and color range as Monel. Most stainless steel eyeglass frames will be marked on the demo lenses Stainless or Stainless Steel and MAY be marked on the inside of the temple as well. If no markings are present you may not be able to tell the difference between a Monel frame and one made of stainless steel.

Advantages of stainless steel frames:

• Can be light in weight because of reduced material
• Very strong
• Very little chance of allergic reaction to metal
• Holds color well
• Attractive appearance
• Holds adjustments very well

Disadvantages of stainless steel frames:

• Limited range of colors.
• Colors tend to be matte in finish.
• Temples are rarely made in any shape other than “paper clip.”
• Larger frames can become heavy.

3. Titanium is used in many mid-range and many high-end frames. Since it comes in a wide range of colors, plating, and styles, it is not always possible to spot a titanium frame unless it is marked as such. Its extreme light weight may tip you off. A titanium frame of equal size may weigh half as much as an identical frame in Monel.

Advantages of titanium frames:

• Titanium is hypo-allergenic: it will not cause reactions with skin.
• It is extremely lightweight.
• It is 100% corrosion proof.
• Extremely durable. A well-made titanium frame can last for years.
• It’s very strong.

Disadvantages of titanium frames:

• Titanium is not easy to manufacturer, and not all companies provide the same quality of production.
• Frames can be legally labeled 100% titanium, yet contain other metals.
• Frame lines may be inconsistent in their quality. Just because a frame is ‘titanium’ does not mean it is a quality product.
• Adjustments can be tricky. If a frame is 100% titanium, it can break easily at weld points if not well-made.
• A well-made titanium frame can last for years which might discourage repeat sales.

4. Flexible or memory metals are metals with flexible properties and are usually a mix of titanium and other metals. The mix is called beta-titanium. These frames will either be all flex-metal throughout the entire chassis and the entire temple, or a mixture of rigid areas and flexible metal. Many flex frames will be “pre-stressed” or curved to act as a spring. Flex metal frames are generally high-end and expensive. Just like titanium frames, not all flex metal frames are created equal. Many lower-end frames offered with memory metal, do not have the same quality of higher-end ones. Brand names for flexible metal frames include, Flexon, Flexolite, Easy Twist, MagicTwist, HyperFlex, CX etc. They are extremely popular for use in children’s frames for obvious reasons.

Advantages of flex metal frames:

• Bend instead of break
• Return to original shape after being bent
• Have spring-like quality that helps hold glasses in place on head
• Lightweight

Disadvantages of flexible metal frames:

• If not well designed with adjustment points built in, frames may be impossible to adjust.
• You may find fitting difficult on people with unusual or very asymmetrical face shapes.
• Some patients cannot adapt to a flexible frame; they actually need to feel the frame on their nose!
• People (especially children) may incorrectly assume that the frame is indestructible, or that it can be bent repeatedly without damage.

Note: Many flex frames are titanium blends. Most often the other metal is nickle so most flex frames, although containing titanium, are NOT necessarily hypo-allergenic!

The second frame category is Plastics and plastics really have one general category and then an odd collection of other materials.

1. ‘Zyl,’ or Zylonite, makes up the bulk of all plastic frames on the market today. If a frame is plastic, chances are excellent that is Zyl. Zyl is also called acetate or cellulose acetate. Although not 100% accurate, plastic and zyl are used interchangeably.

Advantages of Zyl frames:

• Light in weight
• Huge range of colors
• Strong
• Fairly easy to adjust
• Can be molded in any shape and size

Disadvantages of Zyl frames:

• Can lose shape and even be ruined by high heat (dashboard of car in direct sun)
• Will discolor over time
• Will dry out and become brittle over time
• Will stretch out and lose fit in hot weather

Other “plastic” materials in use:

The generic category of plastic frames also includes brand names like Optyl, SPX, Trogamid, and Grilamid.These are variations of Zyl that are slightly lighter in weight, slightly more flexible and have a little greater range of colors available. These Zyl hybrids are prone to heat damage and can snap or split if over-stressed. You need to access the manufacturer’s website or catalog to know how to handle the different materials.

Polyamide (Nylon): These frames are sold under brand specific names. Polyamide frames are lightweight, can be translucent, have high UV resistance, and are chemical resistant.

• Polyamide frames usually have the note “Cold Insert” on the demo lens.

Optyl: Stronger and lighter than frames made of zyl, frames made of Optyl are available. The advantages of Optyl frames are offset by the tricky nature of the material. Optyl is actually a memory plastic which can be heated, formed, and when cooled will maintain the shape until heated again. Lens insertion during finishing can be problematic.

• Frames made from Optyl will usually have Optyl or Opt stamped on the temple.
• Optyl frames often have “sharper” edges or details than common Zyl frames.

Other materials in the plastic category have included:

• Carbon: These were lightweight and strong but nearly impossible to adjust and never really took any substantial market.
• Rubber: Still found in swim goggles and as parts of frames but not used for complete chassis.
• Polycarbonate: Strong and extremely lightweight, it is used in sport safety eyewear.
• Kevlar: These were lightweight and strong, but nearly impossible to adjust and never really took any substantial market.

Flexible Plastic Eyeglass Frames

Flex plastic has all the advantages and disadvantages of flex metal with the added advantage of even greater weight savings. A quality flex plastic frame when combined with lightweight lenses are the lightest eyeglasses made.

Flex plastic frames do not have any wire core to help with adjustments. Just heat them pretty hot, hold in the shape you want, let them cool down, and they should hold the new shape. Since there is no wire core, flex plastic temples can easily be trimmed to different lengths.

Note: Manufacturers will often mix several materials in a single frame. When a frame has a mix of materials – for instance, metal temples and a plastic front – you note the frame material by the chassis or frame front. The lab will need to know the material of the eyewire in order to set their machines in the correct mode for cutting out the lenses.