# Optical Forums > Ophthalmic Optics >  question for lab managers....

## jb@kso

Hello everyone. I have had a rash of jobs coming back with cracks in them in the last few weeks. My first thought was stress cracks from the lenses not being sized properly. But then I started seeing it in even some grooved rimless jobs. Point being, I've seen it in metal frames, zyl frames, and rimless. Not wanting to point finger at manufacturer yet (*wink), are there any other issues I should be looking at? Could it be something as simple as cold weather? Something about the edging process? 

Thanks in advance!

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## leestaniforth

hi. it depends on what you mean by cracks... where abouts are they? edge or centre??. if this is happening with all lens types there must be something that is common with all the lenses.. ie the process or the equipment they are produced on. More info would be good?

cheers:cheers:

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## jb@kso

They are small cracks coming in from the edges. Not all of them start at the barrel either. I have seen them even start at the edge and come in even from the 6 o'clock position.

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## DragonLensmanWV

What types of lens material?

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## chip anderson

Probably made up Nawth and blanks were too cold.

I can remember getting glass blanks in from Corning in North Carolina. We were in Houston where it was 85 degrees. Took four days for the blanks to un-freeze enough to get them out of the cartons and a full week before they could be put on the generator without shattering.

Chip

An before you tells me this is plastic you be talking about, plastic is sensitive to temperature too.

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## jb@kso

Materials seem to be across the board. I am leanig towards the weather issue also Chip. We are getting this at more than one location. So there are 5 seperate edging machines located in 3 different labs in NE Kansas.

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## Jacqui

Weather. I live in a VERY cold part of Minnesota and I've seen it here unless care is taken.

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## HarryChiling

Poly also has a tendency of cracking if exposed to isopropanol, I have seen our staff try to use alcohol to clean the lenses and they'll be fine for an hour or so then they'll start little cracks.  The change in temperature will do it as well when going from extremes.

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## sharpstick777

I posted in another forum, but we have a rash of poly lenses crack lately around the edges, and not just by the normal screw grommet location.

Sharpstick

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## Leo Hadley Jr

> I posted in another forum, but we have a rash of poly lenses crack lately around the edges, and not just by the normal screw grommet location.
> 
> Sharpstick


So is it only poly?
Ill bet they are being exposed to a chemical somewhere along the way.

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## Jacqui

> So is it only poly?
> Ill bet they are being exposed to a chemical somewhere along the way.


Could be chemical. It could also be a dry cut edger with a semi-dull blade doing it. Chris Ryser and maybe others make a sealer for poly drill mounts, would using this on the edges help??

I hate working with poly !!!!!

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## Leo Hadley Jr

> Could be chemical. It could also be a dry cut edger with a semi-dull blade doing it. Chris Ryser and maybe others make a sealer for poly drill mounts, would using this on the edges help??
> 
> I hate working with poly !!!!!


He mentioned above that there were 5 different edging machines. I suppose they could all be dull.
I am still leaning toward chemical reaction.

Years ago when I was in the corporate retail world:( there was a new product that was a chemical edge polish and or edge tint. Our pencil pushers at the home office jumped on this product and crammed it down our throats. They even forced a quota on us selling the product or face being "written up"
This product seemed to work great until people were coming back after 30 days with edge cracks. I never seen a group of pencil pushers scurry away so fast.:D

As Harry mentioned above, some alcohols will do the same thing and we all know what acetone will do. I suspect there is a chemical being used somewhere along the line. It could even be something in the edger bucket causing it. Lets get the Optical CSI on the case

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## chip anderson

Harry:  

I don't know too much about poly (other than it's definitely not my favorite lens material) but I have handled and worked with a lot of PMMA.
I know that you can just wipe PMMA with alcohol and if viewed with a good light and magnification you will observe fine cracks.   When the doctor sends you a prosthetic eye patient with a crazed conformer you can bet he put it in alcohol to "sterilize" it.   
If for some reason a patient or practioner gets the urge to sterilze a prosthesis an attempts to put it in alcohol it will craze to even begin to disintegrate depending on how long it was exposed.
I suspect that poly may be the same albeit perhaps a bit slower.

Chip

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## mangledmaille

I too had about 10 jobs come in that same way about 3 weeks ago.  all of mine were SV Poly with Avance.  Some of these were cut at the lab for VSP jobs and some I cut.  My lab has been investigating it for me.

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## bob_f_aboc

Keep in mind that a lot of labs use ultra-pure isopropanol.  You might not see anything happen from a wipe with an alcohol pad, but if the trays are being held near the flammable storage area, there may be enough fumes present to cause widespread damage.

I also agree with Jacqui about the dull edgers.  I have seen this happen when lab managers get a little "thrifty."  Generally, you won't see any problems at the edger.  They start to creep up after delivery.

Another question that may point to dull blades; have you noticed any off axis problems with your jobs?  Dull blades pull at the lens instead of cutting cleanly.  If things are regularly coming out 1-2 degrees off axis, you may have found the problem.

My 2 cents worth.

Bob

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## jb@kso

Took the alcohol away from everybody on monday. Just using mix of water and dawn dishwashing liquid to clean things now. I have a feeling this might turn out to be the culprit. I appreciate all the responses, keep them coming if you have anymore ideas!

Stay Tuned......

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## Mauro.Airoldi

Isopropanol and poly?   I hardcoat poly with a coating with a good % of isopropanol.... It is not a problems (we coat 150-300 every week)
can you post a photo of the lens with troubles?

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## laurha

Do you have any other information on this?  We've had quite a few poly lenses come back from the same doctor (more than average) and I'm thinking it is because he is cleaning them with isopropanal.  Are there any technical papers that discuss this or is this just common sense?

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## jb@kso

Honestly, this is the first time I have run into the theory that isopropyl alcohol has this effect on poly lenses. Like I said in an earlier reply, I just removed it from my processes this week so I may not have any conclusive evidence for a few weeks. I have been in this business for 20 years and one thing I have learned is never rule out anything.....lol.

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## Chris Ryser

> *So is it only poly?*
> *Ill bet they are being exposed to a chemical somewhere along the way.*


If it is chemical, fumes or liquids I would suggest you put the sealer on the edges, which seals permanently against such attacks.

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## fjpod

It is very likely due to dull cutting surfaces.  Dull blade on a dry edger or worn wheel on a wet, or a dull bit when drilling.  Labs tend to stretch their blades and wheels beyond limits.  All you have to do is look at the cutting surface under a high power microscope.  When the cutting surface is worn or dull, it "rips" the material instead of cutting it, thereby cracking it.  Kind of like ripping apart some soft cheese with a dull knife or even your fingers.

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## Chris Ryser

> *When the cutting surface is worn or dull, it "rips" the material instead of cutting it, thereby cracking it. Kind of like ripping apart some soft cheese with a dull knife or even your fingers.*


That is correct.................Drillseal will fix the rips and cracks from drilling holes.

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## fjpod

> That is correct..................


Why thankyou, Chris.

So if you are finding your poly jobs cracking shortly after you dispense them, tell your lab to sharpen all the tools in their shed.

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## mangledmaille

i got a call from the owner of the lab that i use today and he told me that he just got off the phone with the regional VP from Essilor and that he had told him that this problem is nation wide now. and that they are dong what they can to get this fixed asap.:hammer:go figure, well off i go to continue to bang my head against the wall

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## MarcE

> Took the alcohol away from everybody on monday. Just using mix of water and dawn dishwashing liquid to clean things now.


How are going to get the layout markings off with Dawn???

BTW, I use denatured alcohol from the paint stripper section.  Is that wrong?  Stressful on AR?

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## Chris Ryser

> *BTW, I use denatured alcohol from the paint stripper section. Is that wrong? Stressful on AR?*


 
Not if used occasionally..........however continous use of lens cleaners containing alcohols will do it.

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## jb@kso

We are using All-Off ink remover for that.

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## chip anderson

You should see the number of PMMA conformers my prosthetic eye patients come in with that are crazed because at the time of surgery the doctor "sterilized" them by putting them in alcohol.

Chip

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## thep

I'm convinced that the basic poly monomer has changed in the last 1 to 1 and 1/2 years. We have had more stress fractures in this material from ALL manufacturers recently. Someone please tell me if I'm nuts!
Janet:hammer:

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## Jacqui

I don't think you're nuts, I've been seeing them too.

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## Leo Hadley Jr

> I'm convinced that the basic poly monomer has changed in the last 1 to 1 and 1/2 years. We have had more stress fractures in this material from ALL manufacturers recently. Someone please tell me if I'm nuts!
> Janet:hammer:


Funny you should say that.........
I was teaching a new technician about optics when I mentioned that poly lenses were bullet proof. I took a name brand poly lens out of the envelope and blasted it with a hammer.
To my suprise it shattered all over the room.

I suspect some polys are being blended for better optics.

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## GAgal

> I'm convinced that the basic poly monomer has changed in the last 1 to 1 and 1/2 years. We have had more stress fractures in this material from ALL manufacturers recently. Someone please tell me if I'm nuts!


 



> I don't think you're nuts, I've been seeing them too.


 
Ditto...

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## JMoondog

> I suspect some polys are being blended for better optics.


I know in the 20 years I have been cutting Poly it is definitly a different breed.

We use to hammer nails to it to show how tough it was :D

I use to tell people to get poly cause will never chip or break, haven't said that in a while

Ric

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## HarryChiling

> I know in the 20 years I have been cutting Poly it is definitly a different breed.
> 
> We use to hammer nails to it to show how tough it was :D
> 
> I use to tell people to get poly cause will never chip or break, haven't said that in a while
> 
> Ric


It's been cracking, chipping, and crazing.  It hasn't been the same beast for a while.

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## hipoptical

Not only poly, but most other materials have changed. Sometimes the biggest changes come when a factory is "relocated" to another country to make processing cheaper. We continue to demand cheaper prices, and failed to realise this comes at a cost. Cheaper usually means cheaper. Rarely does cheaper mean "lower cost".
Pure alcohol (99.999%) is what many labs are using to clean with due to A/R requirements. When you clean mounted lenses with it, you will find that destroying plastic frames is incredibly easy, as well as the lenses. Poly in particular will fracture on the edges when the alcohol sits in points of stress between the lens and frame. As the quality of the lenses continues to decline, the occurrence of stress fractures will continue to rise. It is a nationwide problem because most lenses are made in the same factories overseas.

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## chip anderson

1: Alcohol cannot be made that pure by any means, if it could no one could afford it.
2: Who would waste good Everclear to clean lenses.  If it gets to 180 proof, it's for drinking not wasting on a silly clean up job.

Chip

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## hipoptical

> 1: Alcohol cannot be made that pure by any means, if it could no one could afford it.
> 2: Who would waste good Everclear to clean lenses.  If it gets to 180 proof, it's for drinking not wasting on a silly clean up job.
> 
> Chip


1. Uh-huh, we use it every day. It is expensive, but some people think it's worth it.
2. "We don't have beer. Just tequila."
"What's tequila?"
"Uhh.. it's like beer."

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## Paul van Wyk

We only use alcohol (ethanol) to clean all the lenses we make , CR39 ,hi-index , poly and trivex. 
I never saw any problems with the lenses cracking after edging and we did not get any lenses back from clients.

Paul

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## HarryChiling

> 1: Alcohol cannot be made that pure by any means, if it could no one could afford it.
> 2: Who would waste good Everclear to clean lenses. If it gets to 180 proof, it's for drinking not wasting on a silly clean up job.
> 
> Chip


Chip,
I use Everclear in the lab instead of denatured, less toxic VOCs and when a patient gets outta hand you can take a swig if you wanted and the day get's a little better.:D

(I'm just kidding about the swig, I don't advocate drinking at work.)

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## Chris Ryser

I did a bit of checking into Poly materials. There are 3 main brands in Poly Resins that produce the resins which is divided for industrial and transparent use as the following:

AGENCY APPROVALS OR LISTING : FDA, USP
BASE RESINS TRADE NAMES : Lexan® , Makrolon® 

*MECHANICAL PROPERTIES:*
Specific gravity (ASTM D 792) : 1.20
Tensile strength, Ultimate (ASTM D 638) : 9,000 p.s.i.
Elongation at break (ASTM D 638) : 130%
Tensile modulus (ASTM D 638) : 3.1x10~5 p.s.i.
Rockwell hardness (ASTM D 785) : R118
Impact strength (73° F) (ASTM D 256) (notched) : 17.0 ft-lb/inch
Flexural strength (ASTM D 790) : 14,200 p.s.i.
Flexural modulus (ASTM D 790) : 3.4x 10~5 p.s.i.
Wear factor against steel 40 psi 50fpm : 2500x10~10
Coefficient of friction 40psi 50fpm : 0.38 Dynamic

*THERMAL PROPERTIES:*
Melting point : 310° F
Heat deflection at 66 psi (ASTM D 648) : 285° F
Heat deflection at 264 psi (ASTM D 648) : 270° F
Maximum serving temperature for short term : 275° F
Maximum serving temperature for long term : 240° F
Thermal conductivity (ASTM C 177) : 1.35 Btu-inch/hr-ft~2- ° F
Specific heat : 0.30 Btu/lb- ° F
Coefficient of linear thermal expansion (ASTM D 696) : 3.7x10~5
Applicable temperature range for thermal expansion : 0-200° F

*ELECTRICAL PROPERTIES:*
Dielectric constant at 60Hz (ASTM D 150) (73° F, 50% RH) : 3.2
Dissipation factor at 60Hz (ASTM D 150) (73° F) : 0.001
Volume resistivity (ASTM D 257) : 10~17 ohm-cm
Dielectric strength (ASTM D 149) : 380 v/MIL

*MISCELLANEOUS:*
Water absorption - 24 hours (ASTM D 570) : 0.15%
Water absorption - saturation (ASTM D 570) : 0.35%
Density (ASTM D 792) : 0.0434 lb/inch~3
Flammability (UL 94) : V-2
Weathering Resistance : Limited resistance (UV Sensitive) 

*Annealing to reduce stress*

*Annealing*
Polycarbonate slab (Zelux) has been stressed relieved using Liquo-Temp annealing process. In some instances where extensive machining is required, a secondary annealing of semi-finished parts is highly recommended. Secondary annealing can be accomplished by heating parts at 250"F in a desiccated air circulating oven for one hour per one inch of thickness. After heating, the oven should be turned off and allowed to cool to room temperature spontaneously.




*See the BAYER procedure of Polycarbonate Annealing at:  * 

http://www.bayermaterialsciencenafta.com/faq_pcs/pdf/annealing.pdf

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## chip anderson

I still, despite what has been said on this post, remember from high school science and anatomy classes: 
"About 98% is as pure as a alcohol can be distilled or filtered."   99.9% is not possible.   One can distill and re-distill from now until Doomsday and it will retain at least 2% water.

Chip

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## hipoptical

> I still, despite what has been said on this post, remember from high school science and anatomy classes: 
> "About 98% is as pure as a alcohol can be distilled or filtered."   99.9% is not possible.   One can distill and re-distill from now until Doomsday and it will retain at least 2% water.
> 
> Chip


Thanks for clearing that up...
I'll notify the company that produces the alcohol and puts the label on the drum and provides the MSDS sheet that they are wrong. It's a conspiracy!!

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## Chris Ryser

> *"About 98% is as pure as a alcohol can be distilled or filtered." 99.9% is not possible. One can distill and re-distill from now until Doomsday and it will retain at least 2% water.*
> 
> Chip


 
*Material Safety Data Sheet* 
Ethanol, Absolute *Section 1 - Chemical Product and Company* 
*Identification* *MSDS Name:* Ethanol, Absolute 
*Catalog Numbers:* NC9602322 
*Synonyms:* Ethyl Alcohol; Ethyl Alcohol Anhydrous; Ethyl Hydrate; Ethyl Hydroxide; Fermentation Alcohol; Grain Alcohol; Methylcarbinol; Molasses Alcohol; Spirits of Wine. 

*Percent  * ca.100 
 
https://fscimage.fishersci.com/msds/89308.htm

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## HarryChiling

> I still, despite what has been said on this post, remember from high school science and anatomy classes: 
> "About 98% is as pure as a alcohol can be distilled or filtered." 99.9% is not possible. One can distill and re-distill from now until Doomsday and it will retain at least 2% water.
> 
> Chip


It's usually very easy to reduce the water content now the other alcohols are a bit more difficult to distill outta the process but it can be done.  I would love to drink some of that 99.99% stuff that everyone here is talking about.

Chip here's a recipe to pay the rent:

10 btl - Everclear
20 gal - Fruit punch
2 dzn - Apples halved
2 dzn - Oranges halved
1 x 50 gallon trash bag
1 x 50 gallon trash can

Cut up your fruit in half or quarters doesn't really matter too much how you cut them, stick them in a clean trash bag inside of a clean trash can (by clean I mean brand new) fill with eveclear and punch use a boat oar to mix.  

Put this trash can out in the middle of a field with a bonfire going, get a few cars and trucks in a circe with the radio's blaring and charge $10.00 a head to get in, worked for me a few times. :cheers:

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## obxeyeguy

[QUOTE]10 btl - Everclear
20 gal - Fruit punch
2 dzn - Apples halved
2 dzn - Oranges halved
1 x 50 gallon trash bag
1 x 50 gallon trash can
[/QUOTE]I bet I know what the extra trash bag is for...;)

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## DragonLensmanWV

[QUOTE=obxeyeguy;297743]


> 10 btl - Everclear
> 20 gal - Fruit punch
> 2 dzn - Apples halved
> 2 dzn - Oranges halved
> 1 x 50 gallon trash bag
> 1 x 50 gallon trash can
> [/QUOTE]I bet I know what the extra trash bag is for...;)


For hurling the fruit into?;)

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## nate509

We used to use a ton of poly for any grooved or drilled lens mounts.....We have stopped.  Started noticing a spike in the cracks about 6-12 mos. ago.  I have always known that cleaning agents (alchohol, all-off, etc.) crach poly if they come in contact with areas that are not hard coated, and so we have been very careful about that not happening.  I even experimented with different spray cleaners to see if that made a difference, but it did not.

It's a bummer about this because we also liked the poly due to the flatter base curves that the stock lenses come in.  I know that there are flatter bc CR lenses from the manufacturers but nobody brings them in due to the lack of demand :(

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## Chris Ryser

> *We used to use a ton of poly for any grooved or drilled lens mounts.....We have stopped. Started noticing a spike in the cracks about 6-12 mos. ago. I have always known that cleaning agents (alchohol, all-off, etc.) crach poly if they come in contact with areas that are not hard coated, and so we have been very careful about that not happening. I even experimented with different spray cleaners to see if that made a difference, but it did not.*
> 
> *It's a bummer about this because we also liked the poly due to the flatter base curves that the stock lenses come in. I know that there are flatter bc CR lenses from the manufacturers but nobody brings them in due to the lack of demand :(*


You just said what I have been saying for a long time on Optiboard.

However the optical world is saving money and still purchases lens cleaners that contain alcohols because they can get them for 10 or for 5 cents cheaper than a good surfactant based cleaner that contains no solvents. The same goes for markings removers, there are some on the market that wont affect poly. You  just have to look around to find them.

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## rdcoach5

> You just said what I have been saying for a long time on Optiboard.
> 
> However the optical world is saving money and still purchases lens cleaners that contain alcohols because they can get them for 10 or for 5 cents cheaper than a good surfactant based cleaner that contains no solvents. The same goes for markings removers, there are some on the market that wont affect poly. You just have to look around to find them.


 
Chris, which ink removers won't affect poly that's been grooved or drilled?

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## fjpod

I dunno guys and gals...we edge a ton of poly at my place...into zyl, metal, semi-rimless and 3 piece mounts. I don't want to say never, but we almost never see a cracked lens...not around the holes, not at the edges, not in the grooves...nowhere...  Not 6 minutes later, not 6 weeks later, not 6 months later, not 6 years later.  Maybe I shouldn't say this so loud.

This includes virtually any stock poly lens as well as surfaced, with or without AR. We edge with an Optronics 7E and we change the blade out every 300 or so cuts.  We also change the drill bit at recommended intervals, which I forget what it is.  No fancy cleaners.  No edge treatments. Nothin.  I just don't see the problem.

I can also tell you that poly work that we get in from Davis, will occasionally show stress cracks after awhile.

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## humbleABOCtx

sorry, it's gotta be said.....Poly sux, way too many headaches ,splitting/cracking/starring @ drill holes
i only sell it to pt's already wearing it or upgrade to HIP... 
if we complain enough and reduction is volume is noted maybe mfg will improve it's weak points.

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## humbleABOCtx

added note
just... remembering way back to my lab days not just acetone was a no-no but so was any neutralizer even poly neutralzier. 
we had banned it from using it to remove pal markings and minimized stress crackes...
other reasonable explainaition (process of elimination....)
could be a  dull blade..
chuck pressure incorrect
regardless of the last decadle problems at the lab level; As ya'll were talking earlier, I really believe they've changed the batter-formula

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## gene_bautz

do you use water when when the grinding is on finishing mode? maybe you grind the lens without water all through, you should use water when it is in the finishing mode. and never use acetone.

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## Jan Post

I just read about problems with polycarbonate and wanted to share it to all.  http://www.devicelink.com/mpb/archive/98/05/001.html

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## Jan Post

The following technical article regarding plastics that crack and craze includes polycarbonate. Follow the link for factual eye opener , the article provides good resorces at the end of the article   http://www.devicelink.com/mpb/archive/98/05/001.html

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## Chris Ryser

> *The following technical article regarding plastics that crack and craze includes polycarbonate. Follow the link for factual eye opener , the article provides good resorces at the end of the article* http://www.devicelink.com/mpb/archive/98/05/001.html


This article is fine and dandy.............but there are ways and products to protect Poly from all these problems.

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## HarryChiling

Try Optochemicals drill seal, you can use it on edges and on drill holes.  Our office started to use it for all rimless a year ago and never looked back, matter of fact I dropped and broke the bottle a week ago so Chris can you send me my order I have some drill's waiting.

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## Jan Post

Chris Ryder, I believe much of the problem so far hasent been solved. I previously worked in a surfacing labratory surfacing polycarbonate at Lenscrafters and the standard procedure in processing semifinished blanks, ie progressives, flat top bifocals and single vision polycarbonates was and is, cleaning the lens with isopropal alchohol after it comes off the second fining and prior to going into the coating machines. This step is prior to being sealed is washing the lens with isopropanol alchohol. I always wondered why the company did so many free redos due to cracking and crazing and no one ever gave adequate explaination for the defects.  Its the companys problem now. The problems I see is other outside processing labs do the same proceedure while processing lenses sent to independents

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## Jan Post

Harry Chilling,

Thats great that you seal the drill holes after drilling but if the lens was previously surfaced and most are surfaced to get the proper thickness, it is most likely that the lens was washed with isopropal alchohol prior to you ever getting the lens and once the lens is washed with it, the matrix of the lens is now contaminated with the chemical. We arent talking about wetting a coated lens with alchohol we are talking about a virgin lens that has just had its back surface ground on a generator, fined and polished and then cleaned with isopropanol. It is this step that I believe which can be a flaw in the chain of production which may be universally a problem thoughout the industry. You never know if the problem is due to the lab that sent it to you which processed the lenses.

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## HarryChiling

> Harry Chilling,
> 
> Thats great that you seal the drill holes after drilling but if the lens was previously surfaced and most are surfaced to get the proper thickness, it is most likely that the lens was washed with isopropal alchohol prior to you ever getting the lens and once the lens is washed with it, the matrix of the lens is now contaminated with the chemical. We arent talking about wetting a coated lens with alchohol we are talking about a virgin lens that has just had its back surface ground on a generator, fined and polished and then cleaned with isopropanol. It is this step that I believe which can be a flaw in the chain of production which may be universally a problem thoughout the industry. You never know if the problem is due to the lab that sent it to you which processed the lenses.


I know what your saying iso can crack a lens, but it's also highly volatile so when the lenses are heated before the coating process alcohol will evaporate. Now if the lens is beig cleaned after the fact with iso then there's an issue, not to mention that every eyeglass cleaner I have seen has some amount of iso in it. That's where sealing the edges and the drill holes makes a difference.

Also the process of coating the back side is a chemical reaction, the alcohol may act to roughin the lens surface up to allow for better adhesion.  If we want a material that is more inert than CR39 will do the trick.

If you still think that poly is a problem due to processing just switch to hi-n or trivex if your a safety nut. Too many options available nowadays it's getting harder and harder just to keep up with the various options. I do think at some point int he process they messed with teh recipe for poly but where and how is a mystery to me.

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## Jan Post

In addition to a inherent contamination of the lens, the sales floor often clean the lens with alchohol or alchohol based cleaners, if the lens was a stock lens or surfaced lens, and finished, the edges are exposed matrix. If these edges werent seal treated as Harry Chilling does, the problem persists indefinetly. The question therefore is how many optical establishements actually use this edge and hole treatment which cant account for cracking and crazing. Lets hope a solution is on the rise after so many years of customers coming back in after a purchase anywhere from one week to one year later with edge cracking polys. Since the consumer is always right and you cant prevent them from using alcholol based lens cleaning products, it may be the responsability of the optical firm and the manufactures to seal the lenses and also the need for the sealer manufactureer to guarantee its product for a minimum of one year while the lenses are still under warranty.

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## Jan Post

Harry, the lenses arent heated before the coating process they are drenched cleaned in alcholol as the go into the coating machine with a swabbing pad, no heating of the lens occurs.

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## HarryChiling

Tell your patient's to use Dawn (without the antibacterial or the lemon scented stuff) and bounty paper towels.  Study attached.

Dawn can also do the dishes. :D  Jan it's obvious your good at what you do these little things help the creme rise to the top, it seperates us into different categories of optician.

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## HarryChiling

> Harry, the lenses arent heated before the coating process they are drenched cleaned in alcholol as the go into the coating machine with a swabbing pad, no heating of the lens occurs.


This is the type of equipment I have seen in large labs (document attahced), you'll notice that they use heated air to dry the lenses, most don't use iso in the cleaning process but some do. The idea is you want to get any water off the lenses before coating and since alcohol evaporates before water it is less of an issue than you might think. Of course I may be wrong here the large labs could have the same rinky dinky UV coaters that a lenscrafters has.  You'll be amazed at how dumbed down the LC model is comapred to a highly sophisticated opthalmic lab.

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## Jan Post

I just need to add that it is not Lenscrafters but Coburn procedures. And we know that Gerber Coburn is a leading Lens Processing Equiptment Player in the Industry

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## Jan Post

I looked up the newest Gerber Coburn procedures and it seems they are using ionized water, no mention of isopropanol. I imagine the company is addressing the issue with its newest equiptment. I previously worked for seven years in the surfacing lab and with the equiptment used, the alchohol was used.  I visited my prior store lab and the two lab managers were there and they still were using isopropal to clean them just as I did for seven years. This makes me wonder if any firm with such prior equiptment is still doing the same status quo.

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## jherman

silicon or aluminum, aluminum can have odd affect on some of the mid to hi indexes, fissure being one.

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## HarryChiling

> How are going to get the layout markings off with Dawn???
> 
> BTW, I use denatured alcohol from the paint stripper section. Is that wrong? Stressful on AR?


MarcE, denatured works well it's not isopropyl alcohol. I like everclear personally it's straight from the liquor store, grain exactly like denatured except they don't add poisons. Plus every now and again with those rowdy patients you can take a swig and your day gets better. ;)

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## HarryChiling

> I just need to add that it is not Lenscrafters but Coburn procedures. *And we know that Gerber Coburn* is a leading Lens Processing Equiptment Player in the Industry


No WE don't, I use gerber equipment in the lab I am in now and it's made more for the button pusher. Alcohol is still being used by many in small outfits but the larger labs don't use it and don't have many of the issues your talking about. That's why it's good to constantly keep up with new infromation.

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## chip anderson

Permabrite, formerly Obrite cleaner.  The only spray cleaner that I am aware of that can be used on all spectacle lenses and all rigid contact lenses.   Contains no alcohol, no acetone.  Actually I think it contains mostly EDTA.
Have used it for glasses and rigid lenses for 50 years, my predicessor was using it before that.  


Chip

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## Chris Ryser

> *Since the consumer is always right and you cant prevent them from using alcholol based lens cleaning products, it may be the responsability of the optical firm and the manufactures to seal the lenses and also the need for the sealer manufactureer to guarantee its product for a minimum of one year while the lenses are still under warranty.*


The sealing of the surfaces is done with the hardcoat, but wen cut into shape the edge stays un protected.
That is the place were all the goodies attacking poly can assemlble and do their work. Your lab people most probably are not even aware that this step can be done. It is also additional material and work to do.

I dont think the sealer manufacturer should carry the warranty, as he has no control that this extra step has been applied.

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## HarryChiling

> I dont think the sealer manufacturer should carry the warranty, as he has no control that this extra step has been applied.


I agree with you here Chris, I'd rather you not carry any warranty and me purchase and use your product affordably for all my patients.  Sure it's an extra step, but one that most places don't use and one that definately makes my rimless hands down better quality then the rest.

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## Jan Post

Hey, me again. Was wondering your thoughts regarding polycarbonate warranty? If firms are giving scratch warranty for a year, who ends up eating the cost for lens cracking also? Since it seem the culprit seems to be attributed to alcohol based cleaning, do we contiunue to absorb the cost of redos and refunds for lenses the customer is assuming is the fault of the firm they purchased from. Since we can not blame the customer for inappropriate cleaning and the fact that lens cleaners are marketed as lens and a/r cleaner and contain ingredients not benficial to polycarbonate how do you confront this issue? Who absorbs the cost of selling polys? Maybe we need to switch to a better material even given the postive benefits of poly.

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## HarryChiling

> Hey, me again. Was wondering your thoughts regarding polycarbonate warranty? If firms are giving scratch warranty for a year, who ends up eating the cost for lens cracking also? Since it seem the culprit seems to be attributed to alcohol based cleaning, do we contiunue to absorb the cost of redos and refunds for lenses the customer is assuming is the fault of the firm they purchased from. Since we can not blame the customer for inappropriate cleaning and the fact that lens cleaners are marketed as lens and a/r cleaner and contain ingredients not benficial to polycarbonate how do you confront this issue? Who absorbs the cost of selling polys? Maybe we need to switch to a better material even given the postive benefits of poly.


Our office does, but that's why they call it the "poor mans hi-n".:D

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## pezfaerie

We have seen a mass of poly lenses, no matter the vendor, cracking/splitting like mad. We have tried adjusting just about everything in the edging process to no avail!
You're not alone:hammer:

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## Jan Post

So from the information that everyone is contributing it seems that it is not an issue of the dispenser or the person in the lab finishing the lenses but unknown knowledge on the part of most people both on the retail sales floor and those doing the finishing in the lab. Finished polycarbonate lens edges whose matrix will absorb the chemicals(alchohols and others) of lens cleaners over time causes cracking and crazing of the poly matrix. If our industry, especially the people withing the retail establishments which have to answer to the public consumer giving them credable answers would ultimately cause a solution via informed seller and consumer. At this point most are unaware of the cause leaving sceptisism in the minds of the consumer and the frustration of the selling professionals. Maybe the Optical Labratory Assocations who provide finished coated lenses should provide a bottle when they sell orders to inform the optical practices regarding edge coating thier lenses with the same material they coat thier lenses with. Just a thought to keep relationships all round on better footing.

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## icare

We still stock and use a large amount of poly.  :(  It's too much of a bargain for a large percentage of our market.  Fortunately, we have eliminated the stress cracks in our own finishing process.  They were far more prevalent two years ago when we still edged with a Optimax 401 and hand beveled with a single 800 grit diamond wheel.  We also used poly for all the drill jobs that were finished by our outside lab.  We never did our own drilling and have no plans to do so.  Most of our cracks were in poly drill jobs and higher minus poly jobs that we finished with a heavier safety bevel.  Oh, and they were more frequent during the late winter and early spring.  Our outside lab advised us that they would no longer warrant poly drill jobs for more than six months which was a problem because we always provided a warranty for our patients of one year or more. 

One or all of these tactics led to the solution:

We switched to high-index for all drill jobs.We replaced our edger with a reconditioned Kappa that came with new wheels.We replaced our hand edger with a cheap dual grit model.  We do the heavier bevel first on the rough side and always pass to the fine side being certain to do a quick but consistent light roll across the entire face of the initially roughed bevel.  Lots of water flows and it stays cool.We posted a sign in our dispensary for some time that read, "Just Say NO to Windex and Superglue - It Will Void Your Warranty"  Yes, we actually did this for about a year and it really improved patient awareness of proper lens care.
 There have been no cracks at all in the last twenty or so months.  I'm not convinced that the quality of the polymer has changed, or we're just working around the limits of any newer formulations.

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## Chris Bowers

Ive made a lot of poly lenses and with many different processes. About six years ago we started a few of our labs in a cut to polish surface method. About a year into this I noticed that these labs did not have the problems that our labs that were using a fining process. I also found that when a lab had this problem they also had process variation that rendered less than 2/10ths stock removal. It is my thought that stress cracks come mostly from subsurface fractures at the lens surface and that the edging processes while it can contribute is not the main culprit. Partial validation can be found when looking at the % of finished lens with this as opposed to semi-finished that have these cracks.

Hope this helps,

Chris

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## The Spectacle

> How are going to get the layout markings off with Dawn???
> 
> BTW, I use denatured alcohol from the paint stripper section. Is that wrong? Stressful on AR?


if the lenses have ar use tape it sticks to the in markings and pulls them off the lens. The problem with poly started to become big when they made poly opticaly better mainly for the use of blu-ray disc so now its opticaly better but a greater chance they will crack.

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