Tinting 1.67

[David@LUXE]

Has anyone as of late been experiencing the more than usual difficulties in tinting 1.67? After numerous conversations with various tint suppliers (BPI & Phantom), talks with lens manufacturers (Shamir, Augen and Younger & hard coat suppliers, I am still experiencing more problems that normal. Temps. are correct, time in the baths is fine, ph is okay, tints are not spoiling and the end result more times than we would like to see is a blotchy white affect pointing right back to the front surface hardcoat. We even just set up a new tank dedicated strictly for 1.67 with all the 1.67 preps, etc.... same issues. Any suggestions that anyone has is welcome. I would like to add that these lenses in question are supposedly tintable. We do apply UNNV to the back surface and there is never a problem with the back surface. Obviously, the majority of lenses are made in China and then sold to the major manufacturers who brand and label them. Could this be an issue from the point of origin and how can it be overcome?

[Chris Ryser]

Could this be an issue from the point of origin and how can it be overcome?

If any plastic material is tintable, it can be tinted properly with high energy dyes under the inter action of micro waves. I discovered that between 1997 and 2000 when I researched it and subsequently had it patented.

Low energy dyes as they are used commonly in the optical trade in dye pots, since the mid 1970s, have to be used at temperatures below 100C or they disintegrate very fast.

High index lenses and their coatings do need higher temperatures to tint properly to dark shades in sharply reduced times, like 4 top 8 minutes, while CR39 lens will do it in 60 seconds.

White spots on a tinted surface are not a problem of the material, they are the problem of not having been treated in a well performing modern lens prep, made with the latest surface cleaning chemicals.

You can read up on all of these subjects when you go on my website at http://optochemicals.com and scroll down the main page to MICRO TINTS where there are over 15 links covering just about everything in the new tinting method.

[David@LUXE]

Chris, thanks for the info on your microwave/high energy tinting. However, this is not practical for our lab. We do too many different multi gradients and stripping away tint to create a gradient effect does not seem practical. I should have been a little clearer in stating that the lens material is not getting damaged through pot tinting.... the front surface hardcoat is getting damaged. We tint the heck out of Trivex and understand the need for a tintable hardcoat due to the fact that the hardcoat is what is actually absorbing tint. I was looking for for something related to pot tinting. Have you ever heard if it is possible to apply another hardcoat on a lens that was spin coated?

[Chris Ryser]

David...........There is a fact that optical retailers are so ignorant about, is that most lens materials besides CR39 are not tint able, but can be tinted by forcing the hard coat to accept the dye. This can be done with increased heat of the dye or a prolonged process which can lead to delamination.

Cured spin on, or dipped hard coats of the siloxane or polyester/vinyl type can be stripped of the 2-3 micron layer with the proper chemicals.

There are some hard coat materials that are tint able. However the more tintable they are made, their scratch resistance will be reduced by more than 50%. The more tint able they have been made, the less they will provide protection against scratching. Also, nobody seems to be addressing this fact here on OptiBoard.

In order to have a dark tinted lens with a hard coat, it would make sense to put a hydrophobic coating on top of everything which could provide additional scratch resistance through its slippery effect.

[David@LUXE]

Couldn't agree with you more Chris. What leads me to believe that the problem we are experiencing is do to the manufacturers front surface is that there is no consistency to the problem other than its always the front surface HC is being stripped away. As a test I have applied a coat of UVNV on the existing front HC and the tint absorbs wonderfully. I have them sitting in my office right now. I am concerned that the two HC's may not bond and ultimatley peal away from one another. So, I believe the manufacturers are applying a "splash" to cut corners and this is the problem. What about are your thoughts about applying a second HC on the front surface? Do you know of anything that can speed of the tinting process besides raising temperatures?

[Chris Ryser]

What about are your thoughts about applying a second HC on the front surface? Do you know of anything that can speed of the tinting process besides raising temperatures?

David........................A second hard coat on top of another one is a very tricky idea. It might sound good at the start but but might not work at all or delaminate along the way.

Mass production of lens blanks and stock lenses in CR39 are dip coated with a heat curing system and chemicals made with siloxanes. These siloxanes are in the silicone family which is a basic no stick product.

One solution to faster tinting at least in CR39 would be to purchase uncoated blanks finish them and then tint and HC as the last operation. Howeevr that will not work with Poly and high index.

Some labs claim that they remove the hard coats amd use better more compatible ones for their purpose. That again is easy with CR39 and not for Poly and high index.

In my vue anything that can actually speed up the tinting process in general is the additional use of Micro waves.

[David@LUXE]

Steve, thanks for all your insight. The micro waves is a very interesting process. That in itself opens the door to many additional questions. I may try and give you a call in the near future. Watched the YouTube video and was impressed. Also like how the lens bounced off the floor and the guy just continued to clean. The only way we have removed a hardcoat is through damaging it. We have a very low success rate with removing AR without damaging the hardcoat but at that point the lenses have usually been edged and cannot be hardcoated again. We normally will restart the len(s) if any sort of coating issue.

[David@LUXE]

[Chris]Steve, thanks for all your insight. The micro waves is a very interesting process. That in itself opens the door to many additional questions. I may try and give you a call in the near future. Watched the YouTube video and was impressed. Also like how the lens bounced off the floor and the guy just continued to clean. The only way we have removed a hardcoat is through damaging it. We have a very low success rate with removing AR without damaging the hardcoat but at that point the lenses have usually been edged and cannot be hardcoated again. We normally will restart the len(s) if any sort of coating issue.[/QUOTE]

[Chris Ryser]

The only way we have removed a hard coat is through damaging it. We have a very low success rate with removing AR without damaging the hard coat but at that point the lenses have usually been edged and cannot be hard coated again. We normally will restart the lens) if any sort of coating issue.

David........................If you use a commonly sold powdered AR stripper (Hydrogen Fluoride) and add water to it you will get a 100% Hydrofluoric acid solution, which will lift the AR coating immediately and also attack the hard coat on CR39, as well as damage hard coatings on Poly and high index lenses by turning them opaque.

Hydrofluoric acid is a highly corrosive acid, capable of dissolving many materials, especially oxides. Its ability to dissolve glass has been known since the 17th century, even before hydrofluoric acid had been prepared in large quantities by Carl Wilhelm Scheele in 1771. Because of its high reactivity toward glass and moderate reactivity toward many metals, hydrofluoric acid is usually stored in plastic containers (although PTFE is slightly permeable to it).
see ------> http://en.wikipedia.org/wiki/Hydrofluoric_acid

I first introduced an AR stripper in 1984, which contained an only 11% acid mix between Hydrofluoric and Sulfuric acid with some solvents added into water. This so much lower content of HF took a much longer time span, up to 5 to10 seconds to lift the AR coating before slowly attacking the hard coat. It is also not an immediate danger to the skin and can be washed off easily, before doing so.
Today 29 years later, it is still used by some of the large corporations world wide.