Repainting a lens

illumiquest · May 7, 2018

Weirdly I can't seem to find anything on this.

I have an old Goerz that I've disassembled and would like to repaint since the original stuff was 100 years old and looks like dog shit. I've tried several polyurethane and enamel paints with and without primers and neither sticks terribly well to the sanded and cleaned aluminum (or what appears to be aluminum). The other issue is that the paint is way too thick and fills in the etched lettering and numbers on the barrel completely.

The original paint seems to be alcohol based since it dissolved easily with some denatured.

Wondering what folks have used in the past for making their old glass look good again?

Oh and if there's another forum post about this please redirect me.

John Koehrer · May 7, 2018

Search for firearms paint, it's a two part paint in a single spray can. The hardener container is breached
just before use and usable life is 24 hours, Has to be pretty durable for that use but no idea about use on aluminum.

Duracoat and Brownells Alumahide are two brands

E. von Hoegh · May 7, 2018

It was likely lacquer originally. Sanding it was a mistake, any marks on the metal will show through the lacquer, if it is applied lightly enough that it does not clog the engraving (not etching) which was very fine and shallow on the older ones.
I leave mine ugly, the results more than compensate.

shutterfinger · May 7, 2018

Dead Link Removed
Spray lacquer, allow to cure fully then paint the lettering with Golden heavy body acrylic artist paint http://www.michaels.com/golden-heavy-body-acrylics-2oz/M10196523.html and a fine tip artist brush then carefully wipe off the excess leaving the engraved lettering painted the color you want.
The paint can be diluted 1:1 with water for better flowing into the lettering and has very good adhesion to surfaces.
https://www.goldenpaints.com/products/colors/heavy-body
Check local hobby shops for the lacquer.

Patrick Robert James · May 7, 2018

You need an etching primer for the aluminum, but that is going to add thickness.

You could try blackening the aluminum instead of painting it. I've never blackened aluminum, but I've done it with other metals and it leaves engravings intact since only the surface metal changes. Any coating is minimal. Then paint the engravings if you want and cover it all with a clear lacquer. Typically blackened metals are matt. That should work. It should look pretty good too...

Hope that helps.

tedr1 · May 8, 2018

One possibility is aluminum anodising, an inexpensive and simple process offered at metal finishing shops (plating shops). Surface preparation is important as the anodised layer is very thin, a few thousandths of an inch, it is a very hard thin layer of chemically altered aluminum that may be left the natural color or dyed, black is popular. With a good prior surface preparation the finish can be very attractive and is very durable. It is used for all kinds of things in optics, engineering, electronics, architectural items and so on.

Gerald C Koch · May 8, 2018

Is the job for a camera repairman if the lens has any value.

illumiquest · May 8, 2018

Thanks for the suggestions, I'll look into the aluminum blackening since I hadn't heard of that. Not sure how expensive anodizing is but I'll call around. And Gerald the lens is completely worthless because I don't intend on selling it

illumiquest · May 8, 2018

E. von Hoegh said:
It was likely lacquer originally. Sanding it was a mistake, any marks on the metal will show through the lacquer, if it is applied lightly enough that it does not clog the engraving (not etching) which was very fine and shallow on the older ones.
I leave mine ugly, the results more than compensate.

What if I used really fine sandpaper? And while I appreciate you're leaving yours ugly, I'd like mine to look a little neater since I stuck it on a brand new camera and they don't match. https://www.flickr.com/photos/illumiquest/40869226005/in/dateposted-public/

E. von Hoegh · May 8, 2018

Why on earth did you take SANDPAPER to it at all?
Not too smart, getting abrasives on a lens...
New camera? So what? It's a 100 year old lens. Get a new lens if you want glitz, multicoatings are really pretty to look at.
Congrats for trashing something irreplaceable.

shutterfinger · May 8, 2018

That lens barrel may be magnesium.
Check your local hardware stores for maroon scotch brite pad, excellent for metals.
https://www.ebay.com/itm/3M-Scotch-...023318&hash=item212a6a365b:g:j3gAAOSwidlZaOyE

shutterfinger · May 8, 2018

E. von Hoegh said:
Congrats for trashing something irreplaceable.

If sandpaper was not used on the glass then its not trashed, just disfigured.

illumiquest · May 8, 2018

Von Hoegh I use my equipment, I don't collect it and while I can appreciate that something may be best left alone if it's pristine already my lens was not pristine. The barrel was all kinds of scuffed up there was oxidization starting and the aperture was very stiff. I'd get a new lens if anyone made a 500mm f/4.5 which covered 16x20 and worked better than this one, but they don't. If you want something to be upset about why don't you read the news and stop commenting on posts about lenses which upset you.

Nodda Duma · May 9, 2018

For optically flat black -- critical for controlling stray light -- I used to use Krylon Ultra Flat Black at work and flock it on (spray from about 18" away so the droplets are partially dry when they hit the surface). I don't think you can get that anymore but the Rustoleum flat black spray can for painting grills works almost as well. If you have an airbrush (Harbor Freight), you can airbrush on India Ink and then never touch it with isopropyl or other solvents ever. For really critical shit we would use an epoxy black paint that was something like $500 for 16 oz.

The key is to tag it and not try to brush it on. As you've learned, it'll look like dogshit.

brazile · May 13, 2018

For what it's worth: if it is aluminum, there are chemicals used by the aviation crowd for painting their planes. I picked some up (FAA-approved!) for painting some aluminum fenders that turned out pretty well; it's an etching treatment and primer combo, which you follow up with the spray paint of your choice. Google Alodine.

FWIW, the fenders turned out well and the paint job seems durable.

IMG_1866, Not-racing stripe by Robert Brazile, on Flickr

Ian Grant · May 27, 2018

Nodda Duma said:
For optically flat black -- critical for controlling stray light -- I used to use Krylon Ultra Flat Black at work and flock it on (spray from about 18" away so the droplets are partially dry when they hit the surface). I don't think you can get that anymore but the Rustoleum flat black spray can for painting grills works almost as well. If you have an airbrush (Harbor Freight), you can airbrush on India Ink and then never touch it with isopropyl or other solvents ever. For really critical shit we would use an epoxy black paint that was something like $500 for 16 oz.

The key is to tag it and not try to brush it on. As you've learned, it'll look like dogshit.

I'm wondering if they originally used a shellac base lacquer maybe containing India Ink, or more likely the lamp black itself as you wouldn't want any water present.

Brass lenses are lacquered with Shellac dissolved in alcohol and traditionally used Tumeric and Dragons Blood (a red powdered pigment) for some colouring. I use drops of K6 inkjet pigments. Shellac lacquers are best applied to brass that's been heat up a little, you can use an airbrush, the coating dries to leave a very thin durable layer.

I've never used sand-paper on a lens barrel but I have used 600 grit wet & dry (wet) followed by brass polish, then cleaned well before re-laquering.

Ian

Ian Grant · May 27, 2018

Unfortunately the ideal paints for restoring a black barrel were Lead based, they were banned about 16 years ago here in Europe. They gave a very thin but effective paint finish and because of the Lead content didn't need a primer.

I'd forgotten about them but had a discussion with a friends son last year, he still uses them in small quantities at work, they have a special licence to use them in a highly controlled environment.

Jason, what black paint would you use for a lens barrel ? I found a good Matt Black for restoring the interior of my Petzval lens, I dusted it in as you describe, originally it had been lamp blacked.

Ian

Nodda Duma · May 27, 2018

Outside of $100 / pint stuff, I’d suggest flocking Rustoleum High Heat Flat Black spray paint (green can with picture of a BBQ grill on it), or perhaps try cut shellac with enough carbon pigment to make it opaque (carbon pigment = finely powdered charcoal). India ink could work as well, and in a pinch use a sharpie.

Ian Grant · May 28, 2018

Thanks Jason, I have some Tetrosyl Firecote VHT black paint, I'd guess it's very similar to the Rustoleum High Heat paint, it's designed for similar usage. I'll test it on something, I seem to remember it's very slow drying - I've no current plans to repaint a lens black

Ian

Born2Late · May 28, 2018

Aluminum oxide forms on the surface of aluminum quite quickly and most paint will not stick to it. You can buy special preps and paints that will provide adhesion.

Nodda Duma · May 28, 2018

Yes, Alodine is probably easiest for the “weekend chemist” to apply to aluminum for paint adhesion.

Ian Grant · May 28, 2018

Nodda Duma said:
Yes, Alodine is probably easiest for the “weekend chemist” to apply to aluminum for paint adhesion.

Searching for Alodine in the UK draws no results, it appears to be called Bonderite or Alocrom/Anacrom here. I'd guess I have the chemistry to make up a solution to do the same thing as it's a Chromate treatment.

I've just found a Luc type shutter I'd forgotten about and the paint's starting to flake off the front slightly but the sides and back don't look good and have been badly touched up, I already have another ready for repainting so I'll do some tests then strip the first and prepare it. I'll try the Chromate treatment on some Aluminium sheet first.

Ian

lobitar · Aug 7, 2018

illumiquest said:
Von Hoegh I use my equipment, I don't collect it and while I can appreciate that something may be best left alone if it's pristine already my lens was not pristine. The barrel was all kinds of scuffed up there was oxidization starting and the aperture was very stiff. I'd get a new lens if anyone made a 500mm f/4.5 which covered 16x20 and worked better than this one, but they don't. If you want something to be upset about why don't you read the news and stop commenting on posts about lenses which upset you.

A Dogmar 500/4,5 is an impressive lens - said to be 'a good lens' too. It wouldn't by any chance be the very sample, that Andreas Feininger used for his long distance tele photos of New York in abt. 1950?

Arklatexian · Aug 7, 2018

shutterfinger said:
That lens barrel may be magnesium.
Check your local hardware stores for maroon scotch brite pad, excellent for metals.
https://www.ebay.com/itm/3M-Scotch-...023318&hash=item212a6a365b:g:j3gAAOSwidlZaOyE

Do you really think that a lens, probably well over 130 years old would be mounted in either aluminum or magnesium? When some older lenses were made, aluminum was very, very expensive and I wonder if magnesium was even available. The world began over a billion years ago, not last night.,,,,,,Regards!

lobitar · Aug 8, 2018

If the lens indeed is a Dogmar 500/4,5 and its srl.nr. is roughly in the same range as Andreas Feiningers (112.181 - or possibly 112.187) the lens should be from abt. 1904-5. I think the new alloy of aluminum and magnesium - called magnalium - had just become 'hot' in those years. Magnalium is a high quality alloy said to be easy to machine and surface treat.
By the way - a stunningly pretty piece of machinery, is this camera you have put it on!

Repainting a lens

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