Method for removing scratches from (roughly 1 inch) lens?

Novus plastic polish will do it:


novus plastic polish - Google Search

lasersbee said:

OK.... so you peaked my interest... what is this unique 50+ year old
antique device that uses a 30mm unique lens...:thinking:

Jerry

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I promise I'll show you as soon as I get the glass looking beautiful

Hmm, optics 50 years ago... If it's not a camera lens.. Is it a telescope lens?

Stop guessing guys

It'll ruin the fun if you get it. At least, it'll ruin the fun for me.

Okay, let's respect the man's wishes and stop guessing. It's obviously of some sentimental value to him.

P.S. It can't be telescope or something of alike since the lens got more and more scratched over time, wearing out Just sayin'! Don't hit me!

My Dad is a glass blower and I grew up in a glass studio with furnaces, cutting and polishing equipment glass, diamond saws etc. I recommend the following. carefully stretch cling wrap over the lens, without any creases. Pour plaster of paris into a plastic bowl, then suspend the lens (wrapped in plastic) into the plaster, to create a negative mould.
Once set, take a piece of felt, wet it and line the mould with it. I mean the type of felt they use on billiard tables which you can buy from dress-making shops. Felt is a standard carier for polishing compounds when polishing glass. Now what you have is the correct curvature of the lens in negative. Now you'll need a series of silicon carbide grits, starting at about 600 or 800 mesh, then 1200 mesh, and finishing with Cerium oxide. Cerium oxide on felt with polish glass to a perfect surface. The silicone carbide will grind off the surface layers removing the scratches. All the grinding compounds are made into a thin paste with water. You should use candle wax to fix a spindle onto your lens - perhaps a wooden dowel, which you can grip with the chuck of your drill press enabling you to spin the lens in the mould with the grinding compound. You'll need a new piece of felt with each change of compound. Sounds complicated? Because it is! But this will work.

Does this make sense? If you have any questions just shout, happy to help.

edit: just called my Dad and ran this past him. He said mould materials shrink or expand and this approach would be imperfect - and change the curvature of the lens face. He said, and I quote, "grinding scratches out of a lens is not impossible, but it is impractical".

My dad works at Biology department at university, when glass slides get scratched, they use a substance called 'Canada Balsam' this has very low refraction and dries as hard as glass ( My dad once even 'removed' a scratch from a wristwatch with this stuff). I think that this is the most practical example I could find.
Here is the link to a sample on eBay
The procedure for fixing the scratch can be found easily on google, all i know is that it involves heating.
Hope this helps.

If you decide to go with the felt impregnated with grit idea, I would suggest that you use silicone mold agent, not plaster, and SKIP the silicon carbide grits and go directly to cerium or tin oxide polish (available at a rock shop). Or, if you are not particularly worried about maintaining exact optical properties, There is some stuff that we rock collectors use to fill scratches and cracks in polished stones. It is called Opti-Con. It cures by baking in an oven. It's not TOO expensive, works fantastically, but you have to cook it (not good for heat sensitive materials). Cann't wait to see what you have. Good luck with the project!

Very interesting - ok, I'm going to digest this all and see where I land. I ordered some diamond paste in 3 different micron ratings, as well as the Novus Plastic compound that Ash suggested.

If those arrive and don't work, I'll go for the more "complex" and "impractical" solutions

diamond past is expensive, and i'm sure that nova stuff is too. this thing is really important to you isnt it.

michael.

I'm a fucking idiot. I thought the lens was plastic.
Novus won't do shit for glass.

You're right though ash, there are epoxy crack filling and glass gluing compounds with refractive indexes matching glass / gemstones etc. But they won't be exactly the refractive index of your lens and you'll get an abberation, maybe less noticable than the untreated scratch but still evident. It really depends on what this lens is doing and how critical perfect optical precision is in this application!

Silicon carbide might have been better than diamond paste, cheaper anyway. Diamond is very extravagant!

ps. I agree with using one of the modern two part silicone moulding materials to create the die. I've used some of the softer ones making a 'present' for my wife. Amazing technology

Ash said:

I'm a fucking idiot. I thought the lens was plastic.
Novus won't do shit for glass.

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Lol, anyone want to buy some unused Novus ?

I think that cerium oxide jupiter8 suggested is what you want, otherwise it'll leave a lot of fine scratches in there. You'll also need a lapping machine to get it done, something like you see on this site where you have a rag with that cerium oxide and you slowly rub down those scratches until you don't see them anymore. Here's a working link to that site they linked to where you can buy the stuff.

rhd the stuff i posted works i have used it to remove scratches from the lenses from a pair of binoculars I had.

put a mouse pad under the disk and dry polish it if that does not work add water.

rhd said:

Lol, anyone want to buy some unused Novus ?

Click to expand...

Actually. Yeah. I will.
I use the stuff all the time.
PM me a price (incl. shipping)