'un'coating a lens, what can you do? [Archive]

View Full Version : 'un'coating a lens, what can you do?

buzzardkid

02-13-2011, 00:45

Frontman

02-13-2011, 01:02

Toothpaste, Q-tips, and a lot of patience will get the coating off. The toothpaste will clean the lens nicely, without harming the glass.

LKeithR

02-13-2011, 01:06

Interesting. I was actually thinking of posting this question myself. I have a Pentax Super Tak 50/1.4 that sat in a cool damp place too long and has developed some serious mold. Haven't gotten it apart yet but I'm pretty sure the coating is compromised so I thought it might be fun to try it uncoated.

xwhatsit

02-13-2011, 01:58

Toothpaste, Q-tips, and a lot of patience will get the coating off. The toothpaste will clean the lens nicely, without harming the glass.

Really?? I would've thought toothpaste, being a fairly coarse abrasive, would make light work out of scratching the bejesus out of the glass. If that's not the case I'd love to know -- I have a couple of mouldy enlarger lenses with etched coating.

sevo

02-13-2011, 01:58

Polishing is the only safe option - coatings are (mostly) MgF2, and due to the volatility of SiF4 that can't be etched off glass without damaging the glass surface (this is the phenomenon that also causes fungus etch on coated lenses).

YMMV with toothpaste - some has chalk or clay abrasives, others may contain more aggressive silica gel, and some also contain organic fluorides that might attack glass. Polishing red is easy to obtain and much less of a risk...

Brian Sweeney

02-13-2011, 03:31

Jupiters are hard coated.

Cerium Oxide is a traditional glass polishing compound. Lots of "elbow grease" goes into it, or better yet- some polishing wheels are available.

http://shop.ebay.com/i.html?_nkw=cerium+oxide&_sacat=0&_odkw=glass+polishing+compound&_osacat=0&_trksid=p3286.c0.m270.l1313

On the Pentax: be careful of the Thorium Glass versions. You do NOT want to inhale anything that comes off of those lenses. I sent an early Summicron picked up in a trade to Focalpoint, front coating made the lens unusable.

buzzardkid

02-13-2011, 09:33

Thanks for the tips Brian! I looked into that Cerium Oxide stuff and found a seller in the UK that supplies pads for use on a low-RPM drill with it and guess I'm gonna go that way.

Or, I might just put the lens up for sale, so somebody can use it for its focus mount. Not that I have too few 50mm's anyway... there's five already, for five camera's.

Brian Sweeney

02-13-2011, 10:59

The other thing to do- look for an optics module without a focus mount. I've seen a few on Ebay, very cheap. Some without aperture, so the glass can be transplanted.

Jockos

07-12-2011, 08:01

Im trying to uncoat a Industar 50.

Do I need to work all elements/surfaces? Is toothpaste really a bad idea? Could anything else in the household be used for this work?

Brian Sweeney

07-12-2011, 14:08

I have read of people using tooth paste, a mild abrasive. The article stated it took hours to do.

Honestlt, I would buy a new I-50 lens and transplant it into the better fixture. The Rigid optics module is the same as the collapsible.

tlitody

07-12-2011, 14:28

Hello,

I have an old early fifties Jupiter-8 lens with lots of small scratches on the front element. In its current condition its not worth much, both financially and photographically.

What would it take to remove the coating from the front element? Any chemical I could use to remove that will not etch the glass?

I don't think it costs much to have a lens polished which I think takes off any old coating. There was a recent thread on getting a lens coated which talks about polishing. Only one surface and for polish only it may be less than £50.

http://www.rangefinderforum.com/forums/showthread.php?t=106929&highlight=lens+coating

Jockos

07-12-2011, 22:14

I don't think it costs much to have a lens polished which I think takes off any old coating. There was a recent thread on getting a lens coated which talks about polishing. Only one surface and for polish only it may be less than £50.

http://www.rangefinderforum.com/forums/showthread.php?t=106929&highlight=lens+coating
But there's no DIY fun in that.

divewizard

07-12-2011, 22:21

My camera repair guy (http://www.walterscamerarepairs.com/) told me the best thing to use to remove damaged coatings is Brasso. However I have not tried it myself.

awilder

07-12-2011, 22:27

Try using ammonia. I used it once to remove the rear surface coating of a Leitz 21/4 SA as it was partially damaged.

john neal

07-12-2011, 23:11

My camera repair guy (http://www.walterscamerarepairs.com/) told me the best thing to use to remove damaged coatings is Brasso. However I have not tried it myself.

I once did this to remove the coating on a J8 - worked a treat, but took a lot of effort by hand.

I got the idea after using Brasso to remove 60 years of haze on the inside surface of an uncoated Sonnar. Nothing else would shift it - tried all sorts of solvents, ammonia and ultrasonic cleaning to no effect - the Brasso took it off in 5 minutes with no marks on the glass.

Bill58

07-13-2011, 02:03

You could maybe use Polywatch, a product made for the fine polishing of plastic watch crystals. Most watch or jewelry shops around the world have it and its cheap.

Jockos

07-13-2011, 02:44

hlpgtf

09-06-2011, 15:25

I asked this same question on another forum a few years ago - they suggested the following (which I haven't tried personally): "Flitz polish will do the trick. Get the kind for plastics."

peterm1

09-06-2011, 15:43

Never seen "Brasso" in Sweden, but it contains silica powder (according to wikipedia), which I'm a bit sceptic about.

Awilder: How would I go about with ammonia? Just rub it in with microfibre, or let the lens soak?

Brasso is very very very slightly abrasive. It is a liquid and any powder it contains (in suspension) is so fine that all it can do really is polish - it removes very little actual material. Much much finer for example than toothpaste or even chrome polish.

Rob-F

09-06-2011, 16:09

Really?? I would've thought toothpaste, being a fairly coarse abrasive, would make light work out of scratching the bejesus out of the glass. If that's not the case I'd love to know -- I have a couple of mouldy enlarger lenses with etched coating.

I would be concerned about that too. And I question the point of removing the coating. If the lens appears scratched, surely it is not only the coating that is scratched. I suspect the glass itself could also be. So will removing the coating really improve anything? I am inclined to feel that the only thing worse than a scratched coating is no coating. I had a lens whose coating looked awful; but the lens--a Minolta Leica-R 35-70mm zoom--gave good color, and had good backlight/flare properties. The scratches, being perhaps 1/100 of 1% of the total surface area (something like that) made little difference.

Repolishing a lens changes its formula, because thickness is part of the formula. You might want to consider leaving it alone.

Brian Sweeney

09-06-2011, 16:17

I removed a damaged coating from the surface behind the aperture of an early Coated Sonnar. The coating was damaged from the lubricants, not the glass. It came off with ammonia based eyeglass cleaner, and was better after removing it.

Wide-open at F1.5,

http://www.seriouscompacts.com/gallery/data/531/leaf1_f151.jpg (http://www.seriouscompacts.com/gallery/showphoto.php?photo=723&title=leaf1-f151&cat=531)

In my opinion- it was better after removing the damaged coating.

front elements- cleaning marks, will have to be polished off. On a lens like a 1950s J-3 or J-8, easier to replace the front element.

This 1955 KMZ j-3 is much better with a 1980s front element.

Wide-open at F1.5,

http://www.seriouscompacts.com/gallery/data/565/nikki_swing1_j3_f15.jpg (http://www.seriouscompacts.com/gallery/showphoto.php?photo=2249&title=signal-hill-playground-2c-jupiter-3-2c-wide-open-at-f1-5-&cat=565)

The 1980s J-3 was very soft. Good for Parts soft.