No softening required! These plastic frames need little or no heat upon insertion.
Cellulose acetate (also known as zyl) has long been a favorite material of frame manufacturers and designers. While this material requires softening the frame with heat before lens insertion, many other plastics do not. Here’s a look at several of these materials and how to handle them.
Cellulose propionate material uses an injection molding process that results in a thin frame design with good color choices. ClearVision Optical uses this material in its Darcy frame.
Polyamide materials are available in nylon and plastic and have the advantage of being hypoallergenic. Silhouette uses an exclusive and proprietary polyamide blend-known as SPX-to craft many of the company’s frames, including styles 1565 and 4449. SPX’s unique properties allow for comfort, durability, shape stability, and fade-resistant color treatments.
Nylon is a synthetic polymer that is lightweight, durable, and impact resistant. Its strength and flexibility make it ideal for sports and sunwear applications. There is some adjustability to nylon when heated. Due to its manufacturing techniques, there is a wide range of color and surface options. Sports eyewear featuring this frame material includes the Nike Premier 6.0 and the Nike Golf X2 Pro Sunglass offered by Marchon.
Ultra fine but incredibly strong, nylon fiber doesn’t require high heat for lens insertion. The Liteforce line from Luxottica’s Ray-Ban employs this material. Style RX7069 boasts a flattened bridge and the brand’s signature rivets.
Polycarbonate material is a thermoplastic that is virtually unbreakable and is ideally suited for sports and safety eyewear applications. Due to the stiffness of the material, however, few adjustments can be made.
A common factor that all these materials share is the need for little to no heat during lens insertion. Frames needing a “cold snap” insertion require the ECP to use different techniques when edging and mounting. These frame materials can be unforgiving with regard to bevel placement and sizing, which can result in lens spoilage, so precise edging is needed. If you follow certain guidelines, glazing these space-age frames will be a snap-literally.
Make sure your edger is running true to size. Even a 0.1 mm change could result with a broken frame or loose lens. When it comes to tracer/edger combinations, make sure your edger is running true to size with the tracer. If not, consult the manual or manufacturer to recalibrate.
For precision, measure the eyerim’s circumference, not its boxed dimensions. The circumference measurement provides for a much higher degree of precision. Cut the lenses approximately 0.75 to 1 mm over the size for the eyerim’s circumference measurement. Be sure to measure each eyerim separately since they are almost never exactly the same.
Since most of these frame materials can have their size or shape altered by heat, the frame will not assume the shape of the cut lenses like cellulose acetate does. This means that you must cut an appropriate bevel placement for the lens’ curvature in relationship to the frame’s eyerim curvature. Contemporary edgers have this capability.
If you have cut the lenses accurately, they will be slightly oversized for the respective eyerim. Position the lens with the frame for insertion as you would a zyl frame and push the lens into place. It’ll take some effort because the lenses are larger than the eyerim and the frame material resists stretching, but it will snap into place.
Using frames that allow little or no heat for adjusting or glazing is a snap once you know what to do.
Richard W. McCoy, LDO, ABOC, NCLC, is an opticianry instructor at Hillsborough Community College in Fort Myers, FL.
WHERE TO FIND IT:
ClearVision Optical Co. 800.645.3733 • cvoptical.com
Luxottica 800.422.2020 • luxottica.net
Marchon Eyewear 800.645.1300 • marchon.com
Silhouette Optical, Ltd. 800.223.0180 • silhouette.com