tinted lenses

[harry a saake]

anyone know why it is if you take a pair of tinted lenses and hold one over the other you always see more red?

[JRS]

Both lenses have the red, you are just viewing the 'sum' when stacking the lenses as you describe. Tinted lenses displaying reddish tones usually indicate a low (lower than the optimum 205 degrees) tint tank temperature. If I remember correctly, red molucules are small, hence they are absorbed easier into a lens. Lenses that are not hot enough do not open their pores up enough to absord the other colors in the dye. If you are interested in some documents on the science of tinting, I will e-mail you some info.
E-mail me @ techengineer@compuserve.com if you want it.

[Darryl Meister]

Hi Harry,

I'm no tinting expert, but I can give you some of my own anecdotal comments and some recommmendations from a tinting manual I have (from SEEgREEN, for those who are interested in obtaining it)... First, though, note that grey dyes are made up by mixing equal quantities of subtractive primary colors: cyan, magenta, and yellow.

1) Lower than recommended dye temperatures will shift your tint hues to the red end.

2) Older dyes might make lenses appear reddish (perhaps because the other primary pigments are depleting faster).

3) Inspecting lenses under incandescent lamps, which put out more light on the red end of the spectrum, will also make your lenses appear more on the red side.

4) Perhaps... Lens surfaces or coatings may accept the different dye constituents at different rates? A lens preparation or color priming solution might help in this case, in addition to distilled water.

5) Lastly, according to SEEgREEN, a grey tint that will be used for a dark color (especially on a high minus or high plus lens) must have more of a green tone, in order to avoid reddish casts.

When you stack two such lenses together, you are simply compounding the redness effect -- making it more apparent.

Hope that helps...

Best regards,
Darryl

[Diane]

I have to say this is perhaps one of the most ordinaryly useful threads that I have read recently. This is information that can be used on a daily basis for average Opticians. With all of my studying on tints, (not just for cosmetic pusposes) I suppose that I just never ran across the issue of tinting temperatures affecting the red. It really makes sense. I did recognize the age of the dye, and also the usefulness of green or yellow in affecting the red, but this I can pass along. :)

Thanks,
Diane

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[Darryl Meister]

Hi JR,

That was a very informative article... Perhaps you can make it availabe from the OptiBoard download site in the future?

Best regards,
Darryl

[JRS]

Would be happy to pass it on to the board - soon as figure out how the new site works (LOL).