When there is a sudden temperature change it just has to happen......................
Quote:
Originally Posted by
AndyOptom
Does this weather pattern sound suspect for potentially shortening life of lens AR? Logically I think so, but given my slipping memory...
My own slipping memory reminds me of the old days in Switzerland, and no acting up of AR coatings in winter weather and coming into the warm house from extreme cold temperatures or vice versa.
However in these days the AR coating was applied only on glass lenses. The SIO2 layer (which is Glass) was totally compatible with the basic glass lens and there was no expansion or contraction problems.
This all changed when plastic lenses hit the market and became the run of the mill materials for optical lenses. The plastic lens, whatever material, has a different expansion coefficient than the AR layer which is SIO2 (=glass).
When there is a sudden temperature change it just has to happen. This is no material, nor manufacturing defect, it just has to happen. I am only surprised that it happens also in your corner of the world, but then you explained also the the big thunderstorms with a sudden large temperature drop, that makes sense.
There is also one way to save a lens if it is made from the right plastic material, is to use a good AR stripper which can be done in an office in a few seconds and the lens is fully saved, with the defective AR coating removed.
If I would be back in the retail, I would only sell AR coatings on CR39 lenses which are indifferent to an AR coating stripper, which will turn most other materials into a white opaque, unusable lens.
I came out with the first commercial AR stripper in 1984 that was ready to use, with a very large dilution of the necessary acids down to 13.5%, which made it a non dangerous product for professional use, as well as transportation. We have been selling it ever since.
Lenses that have been stripped can be re-coated by neutralizing the leftover acid in the lens pores, or can still be worn and used without the AR coating.
However anybody wearing Polycarbonate or other high index lenses is out of luck, as these lenses will turn white opaque when stripping, and new lenses have to be made.
There is nothing that can be done, when sudden temperature change hits those lenses, the glassy AR coating is solidly adhering to the basic lens, and will craze when the base is expanding or contracting. No manufacturing problem in that case.
This is a problem every retail optician should advise their patients ..............
Quote:
Originally Posted by
Chris Ryser
There is nothing that can be done, when sudden temperature change hits those lenses, the glassy AR coating is solidly adhering to the basic lens, and will craze when the base is expanding or contracting. No manufacturing problem in that case.
This is a problem every retail optician should advise their patients of, when they sell those highly expensive AR coatings.
So what can be done to get around this problem were you can not blame the lab or the manufacturer for having supplied a faulty lens ?
A)
At point of sale the customer should be advised of the fact that by purchasing AR coatings of any kind and make, added to the lens they are purchasing, can craze in mid to extreme sudden temperature changes.
B)
If the customer purchases any lens materials as, Polycarbonate or other high index for one reason or another, the lenses can not be saved if they encounter any sudden temperature changes, and the coating will craze and the lenses have to be replaced.
C)
The perfect solution is to stick to CR39 material for AR coatings, which can be saved without any problem, by stripping and recoating them, or just by using them without the AR coating.
However this thread was started in Malaysia where I have never been,.................
Quote:
Originally Posted by
Robert Martellaro
It helps for sure...........if you think about it, and remember it.
However this thread was started in Malaysia where I have never been, but knew that it was in a hot/warm geographic area and never even assumed that they could have anything else in sudden temperature changes than going from the heat into the air conditioned house.
So it has been a new version for a theme of "deja vu" like most themes in threads, that come up periodically in a new version.
rapid 100 degree F temperature changes (-30Foutdoors to +70F indoors, etc.)..........
Quote:
Originally Posted by
Sibirer
I see lenses exposed to rapid 100 degree F temperature changes (-30Foutdoors to +70F indoors, etc.) every year and they hold up very well with very few failures on lenses that weren't already damaged.
Thank you for your post and opinion ...................
How did the few failures you had get damaged prior to exposure to the described rapid temperature changes ?
Now I am really wondering what all this scientific talk and knowledge is,............
Quote:
Originally Posted by
Sibirer
I'm consistently amazed year after year how well modern AR stacks hold up to extreme temperature swings. I see lenses exposed to rapid 100 degree F temperature changes (-30Foutdoors to +70F indoors, etc.) every year and they hold up very well with very few failures on lenses that weren't already damaged.
Most pre-existing damage was due to deep scratching into the substrate, severe scouring of the top coat, or DEET exposure.
Now I am really wondering what all this scientific talk and knowledge is, about plastic materials contracting or expanding, depending on the temperature and its changes is, when an experienced optician who lives in the middle of ice cold Alaska, says it is not so.
Before knowing anything about glasses, I learned in school why the railways always had this repeating nose when running on their rails. It was the gaps where one rail joined the next to provide a space for expansion or contraction, because of temperature changes.
This has nothing to do with application techniques or sloppy manufacturing.
Quote:
Originally Posted by
hosam
I Agree with you
Thank you hosam ...................
You can not change simple physical laws. If two temperature sensitive, counteracting materials are mechanically joined together, there will be a severe reaction, when suddenly exposed to a temperature reaction.
This has nothing to do with application techniques or sloppy manufacturing.
I have handled many of the highest rating cameras made in my life time, and never seen a cracked AR coating on any of them in over 50 years, and they have seen, and be used from the cold South Pole to the North Pole and all hot spots in between, and never had a cracked AR coating.
............very simple explanation these camera lenses, made in glass got the AR coating which is also glass (SIO2) and have a same type material coating. Perfect combination.
This is also one reason while the sale of AR coatings on glass lenses still flourishes in Europe, where opticians only have to deal with scratched and otherwise damaged coatings, which is abuse of the material.
The use of AR coatings on Polycarbonate and high index, is another question, they are two lens materials that can not be stripped when damaged, as the acids will turn the material milky white.
The only plastic lens material that is easily AR coating stripable if needed, is CR39, and is not affected by the process.
There must be another wave of cracked AR coatings coming back .......................
Maybe it is a good idea to bring back this thread as we just passed another 3 weeks of one of the longest cold waves in North America, with snow even in upper Florida.
There must be another wave of cracked AR coatings coming back to the optical stores.
The reason it was brought back is simply for a certain poster to sell AR stripper....
Quote:
Originally Posted by
Uilleann
The reason it was brought back is simply for a certain poster to sell AR stripper.
How wrong you are..........................Being retired, I am not selling AR stripper anymore, however I can still claim to have invented the first commercial version in 1984, and having sold thousands of bottles over the years worldwide, since then.
You could price yourself out of the market ....................................
Quote:
Originally Posted by
Kwill212
Providing a warranty on AR coating for anything other than manufacturer defects is a sham.
Any warranties accorded in commercial life mean, that the end user will receive a replacement value if the product fails in one way or another.
This replacement value is costly and somebody will be responsible for it and have to foot the bill.
If it is the manufacturer offering this warranty, he will decide on the conditions the product might fail, and at what rate. The cost of it is then added to the selling price according to the calculated occurrences.
Should a retailer give higher warranties than the manufacturer, he will also have add the cost to his/her selling price, at a ratio determined.
You could price yourself out of the market