We are using All-Off ink remover for that.
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
Last edited by chip anderson; 03-09-2009 at 08:38 AM. Reason: PMMA
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:
If you have integrity, nothing else matters. If you don't have integrity, nothing else matters
Laramy-K Optical
I don't think you're nuts, I've been seeing them too.
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.
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.
Aim at heaven and you will get earth thrown in. Aim at earth and you get neither. C.S. Lewis
An explanation of cause is not a justification by reason. C.S. Lewis
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
Aim at heaven and you will get earth thrown in. Aim at earth and you get neither. C.S. Lewis
An explanation of cause is not a justification by reason. C.S. Lewis
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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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
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
Aim at heaven and you will get earth thrown in. Aim at earth and you get neither. C.S. Lewis
An explanation of cause is not a justification by reason. C.S. Lewis
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
Last edited by Chris Ryser; 05-26-2009 at 02:14 PM.
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:
1st* HTML5 Tracer Software
1st Mac Compatible Tracer Software
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*Dave at OptiVision has a web based tracer integration package that's awesome.
[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...;)
[QUOTE=obxeyeguy;297743]For hurling the fruit into?;)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...;)
DragonlensmanWV N.A.O.L.
"There is nothing patriotic about hating your government or pretending you can hate your government but love your country."
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 :(
Nate
My Night A/R Guy wears Dididium Lenses
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.
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.
Last edited by fjpod; 06-01-2009 at 07:37 PM.
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