Crazing of Non-AR lenses

[UNIDEC]

I have repeated trouble with Seiko 1.66 high index, non AR coated lenses showing crazing just after 2 years. The range on the product is +10.00 to -15 spheres to a -6.00 cylinders.. The specific prescriptions are in the median range of -4.75 S, -1.00 C 180 A.

I know AR coating have a higher liklihood of peeling or crazing but do the hard coatings of the native lense also show this problem?

[chip anderson]

I have had this problem with an extreemly high percentage of all 166 lenses. Seems to be the hard coat crashing. On some brands you can count on a 60% failure at exactly 11 months.

Use 167 Essilor instead, so far I haven't had a failure with this.

Chip

[Chris Ryser]

I have had this problem with an extreemly high percentage of all 166 lenses. Seems to be the hard coat crashing. On some brands you can count on a 60% failure at exactly 11 months.

Use 167 Essilor instead, so far I haven't had a failure with this.
Chip

Hard coat applications are the decision of the one that applies them. They exist in every variation, the harder, the less flexible. The extreme temperatures either heat or cold will do the damage on extreme hard coating materials as the expansion or contraction of both materials is not the same under such conditions. At that point you will get crazing and delamination.

Retailers will blame the manufacturer for failure while it actually it is most probably the patient who left the sunglasses under the windshield on a hot day. Or the Eskimo who stepped outside from his Igloo to -50F temperatures.

Hard coating is a theme that has not been discussed on this board because everybody assumes that this is a normal occurence on lenses these days.

Hard coating is another additional cost factor which very often is not a necessary item. Lens mnaufactureres make as much money on the hard coats as the manufacturing of the lens costs them.

[UNIDEC]

I don't believe the majority of US customers are eskimos subjecting their lenses to extreme cold and none of the near sighted drivers are removing their glasses and leaving them on a hot dashboard - makes it difficult to drive and walk. Fair arguments would make more sense at this point...:finger:

[For-Life]

I don't believe the majority of US customers are eskimos subjecting their lenses to extreme cold and none of the near sighted drivers are removing their glasses and leaving them on a hot dashboard - makes it difficult to drive and walk. Fair arguments would make more sense at this point...:finger:

You mean a near sighted client would not take his or her glasses off, leave them on the dash board and then go to the beach or play sports outside as they switch into his or her's rx sunglasses?

But Chris, I still find that A/R crazing and the very, very odd hardcoat craze happens with certain manufacturers and hardly, if never happens with other manufacturers.

[Chris Ryser]

But Chris, I still find that A/R crazing and the very, very odd hardcoat craze happens with certain manufacturers and hardly, if never happens with other manufacturers.

For-Life, Hard Coats can be made in any hardness you want, if you have an extremey hard one it just does not flex as much as the lens underneath.

If you have no problem with one certain manufacturer he is most probably using the perfect formula of hardcoat for the lens material underneath plus the final coat of an AR is SIO2 which is glass.

When you hold glass over bunson burner with 2 pliers heat it red hot in the middle you can actually oull it into a thin thread. Those threads made with glass are surprisingly very flexible an can be bent into some good curves. So the Ar coating itself also will flex a little.

Crazing can also occur through the use of lens cleaners containing alcohols as most of them do. Solvent fumes in a workplace can start crazing. There many chemical out there, from common house hold cleaner to whatever that also can initiate crazing.
D

[AWTECH]

Does this crazing seem to happen on both surfaces? or only on the back surface of the lens?

If it is the back surface the problem is the hard coat applied by the lab, not the original manufacturer hard coat.

[For-Life]

For-Life, Hard Coats can be made in any hardness you want, if you have an extremey hard one it just does not flex as much as the lens underneath.

If you have no problem with one certain manufacturer he is most probably using the perfect formula of hardcoat for the lens material underneath plus the final coat of an AR is SIO2 which is glass.

When you hold glass over bunson burner with 2 pliers heat it red hot in the middle you can actually oull it into a thin thread. Those threads made with glass are surprisingly very flexible an can be bent into some good curves. So the Ar coating itself also will flex a little.

Crazing can also occur through the use of lens cleaners containing alcohols as most of them do. Solvent fumes in a workplace can start crazing. There many chemical out there, from common house hold cleaner to whatever that also can initiate crazing.
D

So it is the manufacturer.