For Birding-ausser's information. Great stuff from BirdChat (USA).
Glen Ingram
Brisbane, Australia
>----------
>From: Andy Spencer[SMTP:
>Sent: Tuesday, 30 September 1997 7:13AM
>To:
>Subject: Re: [BIRDCHAT] Binoc Damage to Anti-Reflective Coatings on
>EyeGlasses
>
>Hi Chatters,
>
>Someone complained about lack of durability of anti reflective coatings
>on glasses with abraded rings showing on the front surface of glasses
>after prolonged use.
>
>Here is my experience in overcoming the problem.
>
>Some years ago, I had similar problems--rings developed, apparently from
>the wear of the eyecups on my binocs. When I complained to my
>optometrist (my son), he added a scratch resistant coating to the
>multi-layer coating and voila!!, no more noticeable scratches after the
>one or two years that a prescription lasts for me. I also wash the
>eyecups occasionally.
>
>Also, B&L has replaced eyecups that have cracked from continuous
>'folding' back. The cracked surface exposes the potentially more
>abrasive interior surface--see below.
>
>BTW-- the binoc makers bear the responsibility to use low abrasion
>formulas of rubber for eyecups. In the past, low cost, relatively
>abrasive, mineral fillers such as mica, talc, ground limestone, carbon
>black and many others were commonly used in rubber products. It would
>be interesting to know if the biggies--B&L, Zeiss, Leitz, Nikon, etc have
>even considered this problem??
>
>I've asked my son to add some technical dimension to this posting, and
>his remarks are attached, below, with his permission.
>
>Andy Spencer West Bay, Old Mission, Michigan
> On vacation
>
>--------- Begin forwarded message ----------
>From:
>To:
>Subject: Re: A-R Coatings
>Date: Sun, 28 Sep 1997 19:41:22 EDT
>
>>From Gary Spencer O.D., private practice optometrist in Muskegon, MI.
>Nearly 50% of my patients have been purchasing lenses with A-R coating
>for at least the last 6 years.
>
>Most Anti-Reflection coatings on plastic lenses can be stripped off and
>either left off or re coated depending on the base material after one to
>two years of wear and tear.
>I wouldn't want to promise that coatings on glass would last any longer
>than on plastic lenses. A few years ago we had problems with Reflection
>Free brand coatings on Varilux lenses. Each time the A-R manufacturer
>tinkers with their multi layer formula to reduce scratching,
>fingerprinting and the like, they risk affecting how it adheres to the
>scratch resistant coatings on the basic lens itself. Even though Varilux
>and Reflection Free are made by sister companies, they had adherence
>problems a few years ago inspiring major labs to search for alternate
>A-R coats. Our local lab in Grand Rapids, MI, one of the 10 biggest in
>the country, started using Zeiss brand A-R coating equipment. Another
>lab in Green Bay, WI also switched to one of several other brands
>depending on lens material the patient wanted. After initial success,
>some of our patients experienced quite a bit of peeling effect after 6
>months to a year of wearing Zeiss coated Varilux lenses. (Others had no
>problems) It appeared that Varilux changed the scratch resistant coating
>again on its lenses and the Zeiss product surface preparation and
>application allowed that base scratch coat to fail so that even
>stripping off the A-R coat would leave a peeled appearance. Within one
>year of purchase, the lab fixed it by remaking the lenses. After one
>year , we are stuck with a less than perfect lens appearance. Meanwhile,
>the Green Bay lab was purchased by the parent of Varilux and Reflection
>Free (Essilor) so they naturally switched back to Reflection-Free brand
>coating and now say it is the best.
>
>On high index plastic and poly carbonate lenses, it is not usually
>possible to strip off coatings without damaging the base scratch coat.
>The heavier glass lenses (which we rarely recommend) were stripped
>successfully the only time we needed to do it. Re coating was not
>advised.
>
>To best prevent binoculars from damaging any A-R coating, keep your
>eyeglass lenses clean and the rubber eyecups wiped clean of dust which
>acts like fine abrasive. Several companies make high-tech cloths that
>lift fingerprint oils and dust off coated lenses without scratching.
>They could also be used on rubber eyecups of binoculars and on the optics
>of the binoculars themselves. Just remember not to scour in an attempt
>to clean. Dishwashing soap (does anyone still hand wash dishes like I
>do?) and water are the best way to flush grit away from the coated
>eyeglass lenses. After blotting dry on a soft clean towel (watch out for
>fabric softener residue) the high tech lens cloth can lift off any last
>smears. Gently wipe from center to edge, not in a circular motion!
>
>Protect your eyeglass lenses from hard plastic edges of eyepieces on
>binoculars and other instruments with self adhesive moleskin pads (Dr
>Scholl brand or generic equivalent). They can be cut to shape with a
>good pair of scissors.
>
>A-R coating has a lot of vision performance benefits so don't be afraid
>to try it. Manufacturers keep on improving its properties. It usually
>holds up at least long enough for you to be ready for your next
>prescription change. My current pair is nearly flawless after 3 years and
>I rub up against half a dozen eyepieces during every exam of every
>patient I see. That is equivalent to a lot of birding use. The only
>thing better is being able to see without glasses at all!
>--------- End forwarded message ----------
>
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