h a l f b a k e r yGuitar Hero: 4'33"
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Despite all sorts of scratch resistant coatings, plastic lenses invariably end up getting scratched. Given the cost of new prescription lenses (mine generally run to several hundred dollars), there is a gaping hole in the market for a low cost way to remove the scratches.
Much has been made of
those devices that remove scratches from CDs - pour a little skunk oil on the CD, insert it in the slot, and turn the crank, polishing the CD smooth.
Let's adapt these CD polishers to be spectacle polishers. I am a little vague on how to polish a rounded surface, compared to the flat surface of a CD, but I assume we can do it with a soft polishing surface.
While there is probably some effect from the filler material having a slightly different refractive index, I am sure it is minor compared to the blur created by a scratch.
Skip Doctor
http://www.digitalinnovations.com/
Fixes CDs by filling the scratches and polishing the surface. [DrCurry, Oct 05 2004, last modified Oct 21 2004]
Baked!
http://store.yahoo....liquidlensekit.html
As seen on TV. Evidently no mechanical gizmo is required. [DrCurry, Oct 05 2004, last modified Oct 21 2004]
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This is a really good idea made even better by the mistake "gaping hole in the marker". If instead of polishing you could use something like a marker pen containing a solution which fills in the scratch, then you use a normal lens cleaning cloth to wipe of anything that's not needed. A bit like clear polyfiller. I would put this as an idea but wouldn't want to offend a professional baker like yourself. |
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I tried to get an optometrist's office to polish scratches out of my plastic lenses. They can't do it for regulatory reasons (I can't recall the regulatory agency in question). In some minute way, it changes the lens' correction factor. Maybe the filler would minimize such issues? |
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Personally, I could live with a teeny tiny change. As you point out, it would be better than the scratches. |
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Yeah, I should think polishing would remove layers of lens until the whole lens was polished down to the lowest part of the scratch, but that changes the optical properties of the lens. A filler is probably a better idea but probably won't be precise. Can we fill, then polish? |
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Of course if it were that easy, lens sales would drop off significantly. On the other hand, donated glasses would have more value. |
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//wouldn't want to offend a professional baker like yourself// oh please! <clutches stomach in mirthful agony> oh please! |
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I find it hard to believe that the scratch resistant coating will come off with alcohol, since that is such a common ingredient in lens-cleaners. I'll look into it. |
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Can they make an "Eyeball Doctor"? A little rotary device that corrects your eyes for perfect vision. It would only have a temporary effect, so it would be fun to watch people using it at the bus stop, during lunch, etc. |
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FWIW, I'd avoid paper anything when cleaning glasses. That stuff never forgets it used to be a tree. Soft cotton or chamois only for me, please |
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I saw something for sale once in one of those catalogs you find in your mailbox sometimes. It was like a chapstick. You smeared it on your glasses, then polished it off. Supposed to remove scratches from plastic lenses. Maybe it was a filler of some kind. I've been meaning to try plastic polish, which did a pretty fair job on my pocket computer screen. You can get that in a good hardware store. Don't ry it on your good glasses though. |
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There is a new product out on the Home Shopping Network that is liquid filler in a pen-type device. It is geared toward prescription lenses and is about 85% effective at concealing the scratch and doesn't change the actual lens prescription. It eventually wears off and has to be re-applied. Once coating lasts about 3-4 months, depending on how often you wipe your lenses clean. |
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In regards to WHY an optometrist can't re-coat a lens with the scratch resistant coating, that is because that coating is a silicon polymer that is very, very thin (microns), thus it would not fill in any visible scratches. This coating is most effective when applied by the lens manufacturer at the time the lens blank is first cast. An optometrist can apply a liquid version of this coating in his office (it's a milky liquid that is heated to about 140 degrees and the lens dipped into it for 5-10 minutes), but the layer that attaches to the lens is once again, very thin and not going to fill in scratches (it does make the lens surface "slick" though, thus it's scratch-resistant properties). |
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More importantly, the reason that a lens can not have the scratches polished out is because even minor polishing WILL change the prescription. Prescription tolerances are very small. They are measured in units called diopters. The tolerance on the average prescription is 0.12 diopter (an eighth of a diopter). These tolerances are dictated by A.N.S.I. and accepted almost worldwide. Polishing a lens enough to remove even a minor visible scratch is enough to change the prescription by 0.50 to up to 2.00 diopters. Most people can pick up on a 0.25 diopter difference in prescription. The average person gets woozy from a 0.75 change in prescription after a prolonged period of use. Worse still, the change is in a confined spot. In effect you would have a lens that LOOKED polished, but that would have a spot that you couldn't see clearly out of anyway. On a practical level, the machines that polish prescription lenses are bulky and expensive, to the tune of 10’s of thousands of dollars sometimes. |
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By the way, most lenses are made from either optical grade plastic (called CR-39), polycarbonate (safety and ultralight lenses), or in a few cases, actual glass. Glass lenses are very scratch resistant, but very heavy and more expensive. CR-39 is inexpensive, but in people that are moderately near-sighted tends to give a "coke-bottle" thickness to the lens. Polycarbonate is very light, yields thinner lenses, is VERY impact resistant, but is a very soft material and scratches easier than glass or cr-39. |
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All right, one last thing. Aside from dragging your lenses across a concrete sidewalk or polishing them with sandpaper, the thing that scratches you lenses the most is.... cleaning them. Most people grab any cloth-like device and rub the lens clean. Contrary to popular belief, it's not the abrasivness of the cloth that scratches them, it's the dirt and grit that was already on the lens that is then dragged across the surface by the cloth, that causes fine scratches. Solution: Rinse your lenses with water and liquid hand soap first, then blot-dry them with any clean cloth. Bounty towels, tissue paper, shirt hem, whatever, as long as its clean and lint-free of course. You'll be shocked at how clean the lens is afterwards. |
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Good grief, someone who knows what he's talking about! That's quite a rarity around here... |
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Anyway, yes, thank you for that. I'll see if I can find a link to that product. And I do clean my glasses that way. Sometimes. |
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