Temperature & latitude change so great will crack polarized polycarb lenses! Help??

**Chris Ryser** · 05-21-2011, 05:13 AM

Another old thread un earthed from the grave yard............................

**EdgeOptical** · 08-20-2011, 02:27 PM

fezz was correct.

if you are allowing your lab to incorrectly dictate what you fit your patients in, then you deserve the criticizm.

the issue is the poly, and there are really too many possible variables to nail down just one.

if you want to be the victim, feel free. or ou can put the patient into the matierial they need and be done with it.

as for a new lab, try perfect optics, or pech. pech will actually tell you the truth... novel concept.

**CalCal** · 08-20-2011, 02:50 PM

although I think trivex would have prevented the cracking, I dont think the temp or the latitude changed were the reason for the crack. I think most likely the position of the groove was the problem.

**AustinEyewear** · 08-20-2011, 07:09 PM

Originally Posted by CalCal

although I think trivex would have prevented the cracking, I dont think the temp or the latitude changed were the reason for the crack. I think most likely the position of the groove was the problem.

Ya, even if Poly Carb couldn't withstand a sudden temp drop, he would have had to be riding down that mountain at Mach 2

**hcjilson** · 08-21-2011, 06:06 AM

Not to whip a dead horse.....BUT I think the problem lies with taking the customer at his word. IF the lenses were OK when they left the shop ( a given) and the polycarb lenses cracked. Logic dictates that it was something the customer did to the lenses that caused the crack. I have spent a half a century in this business, and in all that time the only lens I ever saw crack by themselves was a glass lens with a nick which crinkled during the quenching process coming out of the tempross machine. I actually heard it go! I have never seen a CR-39, or Polycarb lens crack by itself. It is ALWAYS an outside agency that causes it.

**chip anderson** · 08-21-2011, 08:47 AM

I'm with Harry: I am pretty sure that Poly cages are used on brush clearing tractors. I have seen micro cracks in boat windshields but only after years in the sun. Haven't seen it crack from temperture or while in a cold condition. I have seen glass scratch from having snow (in Houston, no less) cleaned off with a plastic (poly I think) comb.
Plexiglass will break when cold, but then that's a different animal.

Will try a few test on some poly at the office soon.

Chip