View Full Version : Blackening a Petzval

9-Apr-2011, 21:08
I was using my 6 inch Petzval the other day to photo the local waterfall when the sun suddenly came out from behind a cloud. Sunlight poured into the lens from approxiamately the 10 o'clock position. I could clearly see the bright brass interior of the lens barrel on my GG. This was an "aha" moment for me! :eek: I think that if I blackened the inside of the brass barrel somehow, I'd be getting better contrast and less flare. But how to do this in a very easily reversible way? My first thought was black tempra paint, but that might be messy and hard to remove. I then thought of some sort of thin black velour (wall paper strips?) or even black tissue paper spot glued in? Surely others have come up with a way to do this?

Kent in SD

9-Apr-2011, 21:21
If you insist on doing it, Wally World has self adhesive flocked black felt 8x10 sheets in their crafts department. I used it successfully to line a 10 inch shiny aluminum top hat board for my Master View so I have no doubts that it works and at least so far, no sign of shedding. For your lens you might be able to just insert it and rely on the curve tension to hold it in place so it could be removed if you decide to do that.

Richard Rankin
9-Apr-2011, 21:47
I also use black flocked paper. The one I use is meant for telescopes, but I didn't nkow Wallyworld had anything like it.

9-Apr-2011, 23:32
Telescope flocking is the way to go. Cheap (<$30) too.

10-Apr-2011, 00:31
If memory serves, the 8x10 sheet from WM was just at $1.00 or a touch higher. I've also used strips from it as light trap replacements on two large format camera backs including the Master View.

Steven Tribe
10-Apr-2011, 02:02
All the old lenses we have that have been blackened inside were done by chemical blackening. Much easier and more permanent that any kind of painting (which will flake) material (that will collect dust) etc. Here is the method - but be careful and project eyes and face against splashing.

"Place an amount of nitric acid (undiluted ca. 100cc) in an earthenware container. Stand it in open place (outside). Add 1/4 oz of copper wire. Wait until all the copper has dissolved. Add about 20cc water.

Heat the brass item in a non-smoking flame (no temperature given!). Plunge the hot item into the acid bath and remove as soon as the hissing stops (DANGER!!).
Remove quickly and drain of excess acid.
Reheat with a non-smoking burner until all the green colour is burned of and has become black. When cool, remove the loose black excess coting with a stiff brush.
You are now finished!"

Obviously you will need a bigger volume of acid etc. if you have a large barrel and you will have to protect the outside of the barrel/threads against being blackened too!!
The text is a shortened extract from Orford's book "lens work for amateurs".
He mentions that the blades of irises should be done separately - then resassembled.
I have not actually done this!

Robert A. Zeichner
10-Apr-2011, 04:17
A common method of blackening reflective areas in lenses is with Kodak #4 brushing lacquer (another thing Kodak probably doesn't any longer sell). This is easily removed with acetone or lacquer thinner at a later date. That said, even this material has a slight sheen to it and may function as a black mirror when rays of light strike it at an acute angle. An alternative, one I used very successfully in motion picture cameras 30 years or so ago, is something model railroaders use called Floquil RR-1 Engine Black. It comes in little bottles, can be brushed or sprayed with an airbrush and thins with Dio-sol, a solvent made by the same company. I believe the solvent is Xylene. Anyway, it's dead matte black and works great. Having said that, I did a little Googling and lo and behold, Testors took over the Floquil line some time back and changed it all. Maybe you know some old model railroaders who have a stash of the old stuff?

The title of your post, to someone unfamiliar with lenses, might sound like a recipe for preparing fish.

10-Apr-2011, 05:33
Wasn't lampblack used early on? I recall reading something where the empty barrel would be held over a candle or an oil lamp to get some of the soot on the inner walls. I wish I could remember where I read it.

10-Apr-2011, 05:40
I think you are onto something Kent. I didn't notice before the lens wasn't black inside. All of the lenses I've ever handled from that period (hundreds) were chemically blackened or perhaps painted somehow. I've never seen material used on the inside (other than between the barrels for a gasket) until much later specialty lenses. Still, I'm sure it would work. Or just mask off the outside, take the glass out, and spray some flat black paint in it. Whoever owned it in the past somehow got the black out of it, or it aged off. Adding black back into it won't hurt anything....

10-Apr-2011, 07:27
I think I'll start by trying the adhesive flock paper. That would be easiest to reverse. A sooty candle might be my second choice. Fooling around with an acid bath is something I likely won't try, LOL! While I did that sort of thing in my college chem classes, my fear is I'll end up dissolving the lens barrel or something.

Kent in SD

10-Apr-2011, 11:51
A company called Birchwood-Casey makes a product called Brass Black, which will chemically blacken clean brass. A really good hardware store might have it, or perhaps a local gunsmith.


Steven Tribe
10-Apr-2011, 12:02
The gunsmith product sounds like a similar process - just more environmental suitable.
When I can find my primus I'll do an experiment on a piece of brass to get an idea of temerature needed and masking the outside - and will post results.
The finish on old lenses does look like candle carbon - tiny particles of "soot" - but it must be a burnished stable oxide of copper and/or zink.

I have an address for "vegetable black" - mat black application, the next best solution, but this is from 1931.

10-Apr-2011, 13:58
A company called Birchwood-Casey makes a product called Brass Black, which will chemically blacken clean brass. A really good hardware store might have it, or perhaps a local gunsmith.


I don't know about Brass Black but they do make a product called Sight Black. It's a spray on/wipe off stuff that I use to black my sights for pistol and rifle competitions. It runs around $8 for a 3.5oz. can. It's basically spray on lamp black and can be a bit messy to clean up.

13-Apr-2011, 21:35
I'm a metal smith and can recommend the "Midas Black/Brown Patina" from RioGrande can be found at riogrande.com. It is toxic but not very, just were rubber gloves, doesn't even have bad fumes like liver of sulfur (used to blacken silver). I use it to darken all copper based metals. Just paint it on and the rinse with water. Will give a very matte finish if you don't rub it much. Works best on clean warm metal.

Mark Tweed
14-Apr-2011, 11:19
If you're doing the complete interior of the lens casing it sounds like the brass blackening treatments would work best as they wouldn't interfere with the fitting of glass elements (where flocked adhesive paper would because of its thickness - also trying to apply the adhesive paper to the inside of a barrel would be a tricky process). If it's just the front barrel extension (what extends forward of the front lens element) that needs to be blackened, a quick solution is to line it with black kraft paper tape. You can pick up a roll at any fine arts store. It's a 3/4" wide and has a matte black finish with a slight texture to it which would assist in scattering any reflected light.

This tape, like the flocked paper, however would be difficult to apply to the deep insides of a brass barrel.


21-Apr-2011, 17:51
When I was doing recementing and barrel restorations I tried just about everything mentioned here. From experience and simplicity I use Floquil Engine Black. It is also known as a Mil Spec Optical black. It is applied with an airbrush while the barrel is turning in a lathe. You can also use an old phonograph to turn the barrel. This paint is available from any good train hobbyshop. It can be brushed but an airbrush works best. Tonight I looked at a lens I blackened 33 years ago. It has not peeled or flaked.

22-Apr-2011, 08:07
If memory serves, the 8x10 sheet from WM was just at $1.00 or a touch higher. I've also used strips from it as light trap replacements on two large format camera backs including the Master View.

The difference between the stick-on felt at the local store and flocking paper is that the former will dump lint if disturbed. I would not worry about that much in the camera, which I can clean out routinely, but I'm not sure that would be my choice for the interior of the lens.

But I think the felt would stick better to convexities. I've had trouble with that. But it's been fine on the insides of concave shapes. I agree, though, that cutting it and applying it to the inside of a barrel will test your vocabulary of nasty words.

If you use brass blacking or optical black, make sure the brass is very, very clean first. That usually means applying a chemical degreaser to remove any wax or skin-oil residue. Any trace of those will either leave patterns in the blacking or cause an applied paint to peel. Brass musical instruments are treated with a hot spray degreaser in a booth before lacquering--getting it clean is nastier than applying the black.

Rick "thinking a very deep compendium shade might help, too" Denney

22-Apr-2011, 13:05
Ok, this my sound too simple but can't you just hold up the dark slide to shade the lens before taking the shot??

Louis Pacilla
29-Apr-2011, 12:18
I remember reading a thread regarding a warning of lead paint used to blacken the interior of early lenses I just came across it. Therefor I'll post it. I do not have a position on the subject ( internally painted/candle carbon blackening ).

Here it is :

" Brass lenses WARNING Lead Paint"
"Just a note of caution for those of who like to play, take apart, and clean older brass lenses - many *may* contain lead paint. While testing some other products for lead content I casually tested a few lenses I own and rougly 1/3 contained lead in the black paint that is used internally on these lenses, inside the lens hoods and on the reverse of many flanges. The worst offender was an 1860 CC Harrison lens... Almost all Darlot lenses did NOT contain lead.... just a note of caution...."



If CC Harrison Candle blackened the interior of their lenses they apparently painted Dans (w/ lead paint to boot). The ever popular Darlots are good to go. lick em' if you want.:eek: