Mineral Glass still most frequently used material

[Chris Ryser]

Going through the Essilor website I found the following statement:

Mineral glass



Properties

• Robust
  

• Hard
  

• Breakable at ambient temperature
  

• Transmits visible light
  

• Surface can be polished to be made transparent and non reflective
  

Towards a new standard
The 1.5-index mineral lens is the most frequently used material at this time. It is made of 60-70% silicon oxide and of other components (calcium, sodium and boric oxides).
However, 1.6-index lenses are tending to become the new standard. This higher index is obtained by adding a significant share of titanium oxide.



Refractive indexes according to the type of material


Material Refractive index

Mineral glass1.5 to 1.9
Organic glass – low and medium index 1.5 – 1.56
Organic glass – Polycarbonate 1.59
Organic glass – high and very high index 1.6 – 1.67 – 1.74



See at -------------> http://www.essilor.com/the-materials


which would translate to: that we big time plastic users in North America are still the minority. :D

[Jacqui]

Why doesn't this surprise me?? I see a lot of talk about glass and it's superiority to plastic from people in Asia, Africa, Central and South America.

More later when I have more coffee. :D

[For-Life]

Most of that is due to its use in Third World nations. The cheapness of the material is its reason for use.

[Golfnorth]

Most of that is due to its use in Third World nations. The cheapness of the material is its reason for use.

Cheapness of the material? Glass is twice the price at the surfacing labs.
I don't do them for Social Service as I end up losing money on them due to
the outdated price lists that are used to bill the government.
I don't understand the whole thing.

Regards,
Golfnorth

[FVCCHRIS]

I'd have to suggest that in 3rd world countries the scaricity of lawyers also permits the use of glass at a higher rate.

[For-Life]

Cheapness of the material? Glass is twice the price at the surfacing labs.
I don't do them for Social Service as I end up losing money on them due to
the outdated price lists that are used to bill the government.
I don't understand the whole thing.

Regards,
Golfnorth

it is half the price here

[Jacqui]

Cr-39 is advertised at lower prices in most Third World countries. The people just want something more substantial.

[For-Life]

I just know we were talking to this person who runs an office in Rwanda. This is where we send all of our old glasses too. He deals with the very poor, but he also deals with people who have money. He said with the equipment for, availability and prices of glass, he tends to use it far more.

[Chris Ryser]

Most of that is due to its use in Third World nations. The cheapness of the material is its reason for use.

Actually it is double and triple the labour to surface them in a lab.

Furthermore every single vision lens has to go through the process on both sides compared to plastic which is made in a mold, and once it comes out the mold it has finished surfaces.

If anything between the 2 should be cheap.....it's the plastic job.

[Chris Ryser]

I'd have to suggest that in 3rd world countries the scaricity of lawyers also permits the use of glass at a higher rate.

In most countries around the world glass lenses are still used. Glass lenses break, mostly from dropping on the floor.

Ambulance Lawyers do not exist anywhere else than the USA, the only country in which anybody sues for anything to make a buck.

Glass is still used in most or all countries in Europe, because you can make it as thin as possible and do not have to have minimum thicknesses and there is no need or laws to have them tempered. Even in Canada there is no such thing, unless for childrens glasses.

Ar coatings hold longer and better on glass than on plastics. Lenses barely scratch

[chip anderson]

And let's not forget Glass should please the Greenies as it is evironmentally non-contaminating and eventually degrades to the sand from which it came.
Glass is made from sand which the world has plenty of.
Maybe Obama will make us go back to glass after he destroys the Coal and petrolium industries.

Chip

[MarySue]

Ar coatings hold longer and better on glass than on plastics. Lenses barely scratch

You're joking right? I've never seen an AR coat last on any glass lens. This includes Hoya, Zeiss - or the off brands you see around the globe.

Please say this was an April fools joke posted way early :)
Mary Sue

[chip anderson]

N0 Mary Sue, he's right, ARcoat is glass expands and contracts at the same rate as the glass it's on. If your's doesn't last you need it to be done somewhere else.

Chip

[rbaker]

Glass lenses are superior to any polymer in all respect except impact resistance, which under normal accepted use, is a non issue.

[chip anderson]

Much as I believe in the optical superiority of glass, don'tthink it's superior in reguard to weight of any polymer.

Chip

[Chris Ryser]

You're joking right? I've never seen an AR coat last on any glass lens. This includes Hoya, Zeiss - or the off brands you see around the globe.

Please say this was an April fools joke posted way early :)
Mary Sue

.............there is a Santa Claus

Mary Sue.........................How many Mary Sue's are out there in our modern world ? People like you selling AR coatings probably every day as a premium addition to glasses but have no idea were it came from and when and what it is used for in other fields than just eyeglasses.

Optics has a long history dating back a long time and should be part of an opticians basic education.........because then you would suddenly realize that you latest an newest technologies have been around for an awful long time and have been rehashed and repackaged as the newest and latest science.

History of AR coatings

First developed in the Carl Zeiss laboratories in 1935, anti-refection coatings found widespread adoption after 1945. These first coatings were single layer coatings which optimized transmission for one color only, leading to an uneven transmission behavior across the color spectrum. A significant improvement was introduced in the 70s when multilayer coatings were introduced, offering a further reduction in reflectance from glass-to-air surfaces in a broader spectral range. A highly sophisticated version of this technology is the Zeiss T* coating used in the ARRI/Zeiss Ultra Primes and Variable Primes. (excert from http://www.arri.com/prod/cam/tutoria...p_coating.html )

Leitz , the other large German optical manufacturer was the first to use AR coatings on their pre-world war Leica IIF's 35mm camera lenses called ELMAR lenses which produced way superior pictures over non coated products.

Glass lenses have been used not only on eyeglasses but in instrument optics which is as important as the eyeglass industry and ranges from Cameras to telescopes, microscope, movie projectors, military, medical and thousands more applications that do need AR coatings to produce optical quality. And they are all made from glass.

In the eyeglass industry AR coatings on glass are much superior over plastic lenses. The actual material used to coat AR is silicon dioxyde (SIO2) with added metal oxides for different reason as color hue. (see periodic table at http://optochemicals.com/periodic_table.htm )

SIO2 does adhere automatically to glass as they are in the same family while on plastic lenses you have an unfriendly bond, which is the hardcoat, that bonds to the lens as well as the SIO2 layer. However the expansion coefficient in extreme cold or hot temperature is much different between the materials and can produce failure and delamination.

Actually........no April fool joke but just cold and hard facts. :finger:

[tmorse]

You're joking right? I've never seen an AR coat last on any glass lens. This includes Hoya, Zeiss - or the off brands you see around the globe.

Please say this was an April fools joke posted way early :)
Mary Sue

Besides German cameras such as Leica, the first AR on glass lenses were used to make superior Germay's 'sniper' scopes just before WW2.

[Uilleann]

Except however for the fact that as a general rule, telescope, binocular, microscope, satellite, camera etc. etc. etc. optics are not (as a general rule) wiped or cleaned with nearly the regularity of eyeglass lenses.

I have seen many many glass lenses with a myriad of various AR treatments over the years (most in aerospace applications) that did not hold up well after cleaning. Usually to the tune of several tens if not hundreds of thousands of dollars to replace or repair. There certainly does seem to be some precedent for some glass lenses having a questionable durability when looking at their ability to withstand repeated cleaning. Polymer lens technology certainly differs, but the historical gap in durability and lens longevity does appear to be narrowing more and more each year.

Go ahead and flame away with your knowledge about how wrong the above is if you must. But there is more than one side to this coin.

[Bob MacNeil]

Glass as a substrate has a better adhesion, on the wear issue, I agree with your comment.
Over the years I have closed down a few glass surfacing lines, labs can't afford the lower yield production line. it's a very stable material. Sad to see them go.

Bob

[RT]

I think that you need to work on your reading comprehension, and whoever wrote the Essilor site needs to be a little more precise.

As used on the website, "Organic Glass" means plastic. "Thermo-hardened organic glass" means thermoset plastics, like CR39. So the statement from the Essilor website is telling us that thermoset plastics are the most widely used materials in ophthalmic optics.

Thermo-hardened materials: the most widely used
Example: 1.5 index material
Their many qualities make them the most widely used materials in ophthalmic optics.

"Mineral Glass" means glass. Of the mineral glass usage, the website indicates that 1.5 index is the most common. But that's different than saying that 1.5 glass is the most commonly used material. It's only the most commonly used mineral glass material.

Re-read it.
http://www.essilor.com/the-materials

[renee1111]

.............there is a Santa Claus

Mary Sue.........................How many Mary Sue's are out there in our modern world ? People like you selling AR coatings probably every day as a premium addition to glasses but have no idea were it came from and when and what it is used for in other fields than just eyeglasses.

Optics has a long history dating back a long time and should be part of an opticians basic education.........because then you would suddenly realize that you latest an newest technologies have been around for an awful long time and have been rehashed and repackaged as the newest and latest science.

History of AR coatings

First developed in the Carl Zeiss laboratories in 1935, anti-refection coatings found widespread adoption after 1945. These first coatings were single layer coatings which optimized transmission for one color only, leading to an uneven transmission behavior across the color spectrum. A significant improvement was introduced in the 70s when multilayer coatings were introduced, offering a further reduction in reflectance from glass-to-air surfaces in a broader spectral range. A highly sophisticated version of this technology is the Zeiss T* coating used in the ARRI/Zeiss Ultra Primes and Variable Primes. (excert from http://www.arri.com/prod/cam/tutoria...p_coating.html )

Leitz , the other large German optical manufacturer was the first to use AR coatings on their pre-world war Leica IIF's 35mm camera lenses called ELMAR lenses which produced way superior pictures over non coated products.

Glass lenses have been used not only on eyeglasses but in instrument optics which is as important as the eyeglass industry and ranges from Cameras to telescopes, microscope, movie projectors, military, medical and thousands more applications that do need AR coatings to produce optical quality. And they are all made from glass.

In the eyeglass industry AR coatings on glass are much superior over plastic lenses. The actual material used to coat AR is silicon dioxyde (SIO2) with added metal oxides for different reason as color hue. (see periodic table at http://optochemicals.com/periodic_table.htm )

SIO2 does adhere automatically to glass as they are in the same family while on plastic lenses you have an unfriendly bond, which is the hardcoat, that bonds to the lens as well as the SIO2 layer. However the expansion coefficient in extreme cold or hot temperature is much different between the materials and can produce failure and delamination.

Actually........no April fool joke but just cold and hard facts. :finger:

I think you completely missed the point of Mary Sue’s comment, I don’t think that the smug history lesson was necessary. :finger:The statement you made “Ar coatings hold longer and better on glass than on plastics. Lenses barely scratch,” is your oppinion, not fact. Experience has taught me, that plastic AR coatings adhear better than glass coatings and scratch less. So let's try to play nice, no need for pious remarkes, we're all friends afterall, right? ;)

[MarcE]

As used on the website, "Organic Glass" means plastic. "Thermo-hardened organic glass" means thermoset plastics, like CR39. So the statement from the Essilor website is telling us that thermoset plastics are the most widely used materials in ophthalmic optics.

"Mineral Glass" means glass. Of the mineral glass usage, the website indicates that 1.5 index is the most common. But that's different than saying that 1.5 glass is the most commonly used material.

Exactly. They also talk about "organic glass - polycarbonate 1.59"

We all know that poly is not glass.

[Jacqui]

Over the years I have closed down a few glass surfacing lines, labs can't afford the lower yield production line. it's a very stable material. Sad to see them go.

I hate to see them go too. It's a beautiful material to work with.

[Johns]

[quote=MarcE;277755]Exactly. They also talk about "organic glass - polycarbonate 1.59"

We all know that poly is not glass.[/quo

Oh great! Does that mean that when I sell a pair of polys, I have to call them "eyepolys" instead of "eyeglasses"? :hammer::bbg::bbg::bbg:

[Chris Ryser]

"Mineral Glass" means glass. Of the mineral glass usage, the website indicates that 1.5 index is the most common. But that's different than saying that 1.5 glass is the most commonly used material. It's only the most commonly used mineral glass material.
Re-read it.

That is what is says: Copy and Paste

The 1.5-index mineral lens is the most frequently used material at this time

:finger: