silver image in anodized aluminum?

[gary_deal]

Does anyone know of a process that produces a silver image embedded in an anodized layer on an aluminum substrate? I

managed to get a viable image about three this morning and it's held up to rubbing and sunlight.

Any links or references would be appreciated, this has an interesting look and should have pretty good permanence (being

embedded in what amounts to a layer of sapphire...)

 

Searched the forums with no luck, might have missed something though...

 

-Gary

[colmmccarthy]

Do you mean liquid emulsion on anodized aluminum? You need to be a bit more descriptive.

[silent1]

I've never heard of such a thing -- and much as my curiosity burns, I'd have to advise against giving details in a public forum such as this one, in case your process is patentable. In fact, I'd suggest that a patent search is probably the next step you should take.

[art_haykin]

If you have managed to get a viable image that seems permanent, what's your problem?

[rowland_mowrey]

Patent it.

 

Ron Mowrey

[gary_deal]

I deposited silver within the anodized layer (between the actual aluminum and the surface) to form a photographic image, and it did not involve an emulsion applied to the anodized surface.

 

Found it was long ago patented in various forms and now should be in the public domain......

 

Ok Donald, here ya go:

 

The process involves anodizing an aluminum plate and inserting sensitization, exposure, and development/fixing steps between the anodizing and sealing steps. Basic anodizing is not difficult (http://www.focuser.com/anodize.html).

 

Having a basic anodizing setup already constructed, I lye-stripped a piece of aluminum printing plate (~.005") of it's coating and pulled it before any substantial etch could occur, then rinsed and anodized the piece at 24 amps/sq foot in sub-68 degree electrolyte (~20% w/w H2SO4) for 30 minutes. A second try using a plate etched at 9.25 A/sq foot at 75 degrees for 90 minutes produced less final image density, though other factors may have been involved.

 

Under safelight conditions, I rinsed the plate in distilled water, bathed it in a 6% silver nitrate solution, then in a 7.5% potassium bromide solution with approx. 0.1% ascorbic acid added to adjust ph, then rinsed briefly and allowed it to dry. Since the silver salts were not color sensitized and it was the middle of the night (needed UV but didn't have any), I sandwiched it with a negative and popped it ten times with an old starblitz flash (GN 210?) from about a half inch away.

 

Not having any Dektol at hand, I developed in double strength Xtol stock (because it was handy), for about five minutes, though development appeard to be complete by about three minutes.

 

A simple masked image was the most obvious (done specifically to show clearly whether the idea had worked or not), while a detailed image of a horse standing in front of pipe fencing was much less dense and took some work to see (but held detail nicely).

 

I then rinsed and fixed in 20% sodium thiosulfate, preferring to avoid anything at that point that might dissolve the anodized surface.

 

After an additional wash in tap water and a short rinse in distilled, I boiled the anodized sheet in distilled water for twenty minutes, a standard means of "sealing" the anodized surface. After a final rinse I hung it to dry until the next day.

 

When I say the image is "viable", I mean that you can see it and it doesn't disappear as opposed to there being no image or nothing left to show anyone the next day.

 

The reason that I ask about pre-existing processes is that the image I got didn't have all that much contrast or density, and if someone else has already done the work to produce a more refined method it would be much simpler for me to do some reading instead of starting from the beginning. Better to read a book on photographic processes than to start with salted paper and work forward.

 

I'd done a number of searches through the patent database, but nothing before 1976 can be text-searched (pat no or classification only) so I needed to find a recent patent that referred to earler patents. I finally hit upon the right search string tonight, and it looks like I've got some reading ahead of me.

 

Check out US patent # 4,092,169, it's got plenty of referenced patents to start with including one from 1938, the period where I would have expected this to first be discovered.

 

If you're unfamiliar with the online patent database, go here:

http://patft.uspto.gov/netahtml/search-bool.html

Then enter the patent number, select "1790 to present" from the drop-down menu, and hit search. For pre-1976 patents you'll have to hit the "Images" link.

You can learn all kinds of stuff reading patents....

 

From quickly scanning a couple of these patents, it appears that the cool tip for this is to use a 30% - 50% silver nitrate solution with about 0.5% gelatin, apparently just enough to keep the silver salts within the pores, and to allow it to dry before subjecting it to any of a number of halogenating baths.

 

Ok, looks like that's plenty long enough and tells more than most would ever want to know.

Don't stay up too late reading patents.....<div></div>

[steve_swinehart]

What's different that your doing compared with a standard, sensitized aluminum offset printing plate?

[gary_deal]

Well, if I'd actually known anything about offest printing plates at the time the answer to my original question may have been a bit more obvious. Now that I've read through a few patents I know a little more about it and can say that the chief differences are that the silver image remains within the anodized layer rather than being located on top of the surface or being etched through further processing, and that as far as I can see there's no resulting areas of differing hydrophilic or hydrophobic surfaces - just an unbroken anodized surface.

 

As a matter of fact, the substrate I used was stripped plate material.

 

I now see that the process has been used for many years to produce ID plates and a variety of other things (www.mtlphoto.com), though it seems to be primarily available as a specialized service or industrial grade kit using presensitized plates. I've probably missed the obvious so far, but from what I've found it doesn't apppear to be a regular "applied-to-your-parts" (not *those* parts!) service that you'd be able to get from an anodizing shop. Being a sort of interdisciplinary process (metal finishing versus hand-made photographic emulsions) this doesn't surprise me.

 

The idea was based in a current project (anodizing), which had aspects that I thought might utilize aspects of a previous project (home-made holographic emulsions), and based on the info I've dug up now it may be of use in both photgraphy and anodizing. Since I'm loosely associated with a group of small-time anodizers, such a process & procedure might allow those anodizers to offer an innovative service that may not be readily available elsewhere (even though it's not actually new), not to mention the possibility of metal backed images, dyed or not, and their potential archival qualities.

 

In fact, it's even possible that a diffraction grating could be incorporated into the anodized layer, producing that holo-rainbow effect you see on plastic films and such, without the poor wear characteristics of plastic film or the trouble of roll processing the metal, but that's a post for the holography forum.

 

I found one patent from the '70's that appears to provide almost all the information I was looking for, so I'll be writing myself up a set of formulas and procedures to follow to see what I get. Another patent provides a developer formula that I'll compare to other existing formulae to see what off-the-shelf developer is closest, or just go ahead and mix up. If that all works for me I'll have to get some pinacyanol blue to see about sensitizing the plate to red hene laser so that I can try the diffraction thing. Is there any "rainbow-anodized" stuff out there?

 

If I can get the process to work for me, I may post materials and procedures here (if anyone's interested).

 

Which of course reminds me, is sensitized aluminum sheet for photographers available? I now think I might have seen something like that once, a few years ago.

Cheers,

-Gary

[kymtman]

I had a client bring me a couple of 8x10 photos that were on aluminum to be reproduced. I scanned them with no trouble and printed the repos for them. A friend of mine said that this was a common process, but we did not go into a detailed discussion on the matter. The photos were on anodized aluminum, or seemed to be. Still had its sheen after 20 yrs.