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Medical Forum / General / Vision / March 2006Polish plastic lenses
Is there any way to polish the surface of plastic lenses? They're just slightly abraded, so even if they can't be machine polished, maybe there is a liquid coating that would fill in the light scratches? Not to interrupt all the interesting conversations here (is this really a sci.med group? What happened?) but I have an easy question: >Is there any way to polish the surface of plastic lenses? They're >just slightly abraded, so even if they can't be machine polished, >maybe there is a liquid coating that would fill in the light >scratches? On 3/7/06 11:43 AM, in article 6eor029pmdj2t1aol8l1ht23rr428qamma@4ax.com, > Not to interrupt all the interesting conversations here (is this > really a sci.med group? What happened?) but I have an easy question: [quoted text clipped - 3 lines] >> maybe there is a liquid coating that would fill in the light >> scratches? More years ago than I want to remember, I needed to polish some plastic insulating spacers to prevent surface leakage. I do remember that I dealt with several different plastics such polystyrene and PMMA. I tried several different abrasives such as cerium dioxide and rouge. Each combination of plastic and abrasive seemed to require a different vehicle to prevent scratching. Choice of a pad could be important as well. Bottom line: It can be done, but you have to determine, by hook or crook, which combination will work. When you are done, you will probably have lousy surface quality anyway. Bill -- Ferme le Bush >When you are done, you will probably have lousy surface quality anyway. Isn't it more the case that when you're polishing, you're simply removing material, regardless of how smooth the final surface is? And when you remove material you change the focal characteristics of the lens - so you could remove the scratches, but you'll be baffled as to why the heck you get headaches so much now!! Do they make plastic lenses in poland? well you learn something new every day. dr grant I've heard two basic arguments over the years. One has to do with federal regulations regarding minimum thickness and the other argument has to do with reworking the lens not being cost-effective. DrG > Is there any way to polish the surface of plastic lenses? They're > just slightly abraded, so even if they can't be machine polished, > maybe there is a liquid coating that would fill in the light > scratches? There isn't any product that will do the job (I know there are some commercial products but they do not work). Trying to polish the lenses will mar the optics. Bottom line- new lenses. frank >a liquid coating that would fill in the light scratches? I think that the reason a liquid coating would not work is that it would have to have _exactly_ the same index of refraction as the glass. I once saw a neat experiment - a guy took an empty drinking glass and put it in a big transparent container full of water. You could easily see the facets of the glass in the water, because the water and the glass refracted light differently. He then took another glass and put it in some kind of vegetable oil (forget what kind it was) - and the glass completely vanished. The index of the oil matched perfectly that of the glass. Point being - just 'filling the scratches' won't do it - if the filler refracts light differently than the material it's filling, then it won't work at all. BD >>a liquid coating that would fill in the light scratches? > [quoted text clipped - 13 lines] >refracts light differently than the material it's filling, then it >won't work at all. Good point. I didn't think there would be much refractive effect in a thin layer. I wonder what the mystery vegetable oil was. Sounds like it would be nice to have the equivalent for plastic lenses. Thanks to all for the help. (I'll let you know how the vegetable oil works on my glasses <g>) An "old farm wife" remedy for scratched eyeglasses is good old-fashioned Lemon Pledge. Coat em up, polish it off with a smooth cloth, and you have darn near 48 good hours before you need to do it again. > An "old farm wife" remedy for scratched eyeglasses is good > old-fashioned Lemon Pledge. Coat em up, polish it off > with a smooth cloth, and you have darn near 48 good hours > before you need to do it again. I wonder what Rain-X would do to them? if they survive that and it doesn't work you could try Armor-all? -Quick >I wonder what the mystery vegetable oil was. It was corn oil. I remembered that the TV show I saw the demo on was Daily Planet, so I tracked down a small writeup on the premise... http://exn.ca/Stories/2002/02/04/52.asp "The key here is that the index of refraction of the corn oil and the pyrex glass are virtually identical. Therefore, when the glass is immersed in the corn oil, it bends light to exactly the same degree as the surrounding liquid and thus disappears. There is no way to distinguish it from its surroundings." True, there may be little effect when a material of a different refractive index is used for filling tiny scratches in lenses; but the premise is sound... On 3/8/06 12:45 AM, in article l36t02pu9sil5efehnt3fgt6dkmd5cic8m@4ax.com, >>> a liquid coating that would fill in the light scratches? >> [quoted text clipped - 21 lines] > > (I'll let you know how the vegetable oil works on my glasses <g>) Even if the index is not correct, it might help. It is the relative index that counts. Thus, a lens material of index 1.5 immersed in a water of index 1.33 would have a reflectivity of 0.36% at the interface while the same lens in air would have a reflectivity of 4.00%. Nevertheless, scratches will not reflect the same way as plane surfaces do. Bill -- Ferme le Bush > Is there any way to polish the surface of plastic lenses? They're > just slightly abraded, so even if they can't be machine polished, > maybe there is a liquid coating that would fill in the light > scratches? 600 Wetordry sandpaper does NOT work, it just makes the matter worse. Neither does the plastic polish designed for plastic motorcycle windshields. It doesn't work on plastic motorcycle windshields either. Filling the tiny bubbles in big aero camera lenses with nail polish or black paint worked fine to prefent light scattering, but I'm pretty sure that wouldn't work with spectacles.  SignatureCheers, Bev ---------------------------------------------- "Luge strategy? Lie flat and try not to die." |
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