ask the labs
Working With AR
Susan P. Tarrant
Using hot air blowers, and even bead pans, on frames with AR lenses can cause damage to the lenses. If the temperature is too hot, too concentrated, or applied too long, crazing can occur. We've asked experts in the know to help.
HOT AIR BLOWERS, BEAD PANS, AND AR
Q I know it's not recommended, but if I need to use a hot air blower or bead pan on AR, what is the recommended procedure to avoid spoilage?
A Many factors contribute to the spoilage issue: The temperature of the blower/bead pan, how long the lenses are exposed to the heat, the type of AR, the type and thickness of the lens material, and the type of frame. Are the lenses edged too large? Are they mounted into a wire or plastic frame? Does the frame put pressure on the lenses, making the AR more likely to crack even at lower times and temperatures?
—Bill Markham, technical marketing manager, Essilor of America
A A blower can be used if the frame is put there for no more than three seconds—that's enough time for the plastic to become pliable. The damage to the AR comes from leaving the eyewear in the blower too long. When the adjustment is made, put the frame in cold water. Some dispensers want the blower to do all the work for them—that's when there's trouble with AR.
All blowers are basically the same, so it doesn't matter what brand it is; what's important is the length of time the frame is in the blower.
— Joe Jowanowitch, Homer Optical, Silver Spring, Md.
| MINIMIZING SLIPPAGE |
|---|
| Q How can we prevent problems with slippage when cutting AR-treated poly on our in-office edger? A Several steps must be taken into consideration to avoid slippage. Start with a “stable” blocking surface. Prior to blocking, clean the lens to remove the hydrophobic coating layer that isn't tightly adhered to the AR stack to ensure adhesion to a stable surface. Second, set the lens cutting rate to slow or “soft” to minimize the torque exerted on the lens while edging. An edger that automatically “stabilizes” chucking pressure based on lens material is preferred as too much chuck pressure (one set manually) can cause crazing. Third, choose the right block/pad combo for best performance. The block curve and lens base curve should be matched for optimum adhesion. Intermediate anti-slip pads should be used on the front of the lens between lens and leap pad and proper wet-out needs to be ensured in order for the anti-slip pad to work effectively. Also, place a well-adhered anti-slip pad on the back side of the lens to maximize the lens clamp efficiency. For added insurance, use a matched swivel lens clamp that best conforms to the lens rear curve. |
| — Franco Aluigi, product manager, Santinelli International, Hauppauge, N.Y. |
If you have a question you'd like to have answered in Ask the Labs, send it to Susan P. Tarrant. Email: Susan.Tarrant@WoltersKluwer.com. An archive of past Ask the Labs columns can be found on the Eyecare Business website at eyecarebusiness.com.
![]({"src":"/media/lvnosjaq/52012.jpg","focalPoint":null,"crops":[{"alias":"thumbnail","width":1110,"height":700,"coordinates":null}]})