I've been wondering for a while if this was possible, and geared up for it last year but only just got around to trying. My original plan was to shoot a few digital images of insects using a mega-macro lens, then convert them to monochrome and do contact ambrotypes of them on 8x12" glass. Then reality set in. :)
This posting describes my method and results.
When I did my first ambrotype workshop with the Ostermans, I took along a digital negative that I'd made, which consisted of a few step-wedges and a target image. One of the things we did was enlarge positives onto glass ambrotypes (so my negative was inverted; whatever) using a 5x7 enlarger. That worked fine though there was some perceptible grain. That got me thinking about contact printing and whether it was possible.
I made a test target that looks like this:
(You can download a full size version here if you want it - 3.5M)
It prints about 8x10" on my Epson 2200 using Pictorico 8-1/2"x11" film. You can see, if you look at the target closely, that some of the artifacts in the plate, later, are actually faithfully reproduced from the target.
Step 1: print your image as a positive on Pictorico film using the best resolution you can get from your printer. You'll probably want to do a curves adjustment layer to expand the midtones and lighten them slightly but that will depend on your process and exposure times. I did the target with several wedges and sample curves so that I can just pick the image that looks best off the target then apply a similar curve to my image before I produce the film.
Step 2: Once you have your film, fold back the corners to make 1" approximate "ears" or "handles" - this will prevent you from putting the film inkside down on your plate. It appears that silver nitrate baths rapidly dissolve Epson Ultrachrome ink. Don't ask me how I learned that, OK?
Step 3: Set up your enlarger's light so it casts a sufficiently large collimated beam onto the enlarger table. Put a piece of glass or something down that will keep your enlarger table from getting silver nitrate solution on it. I use a 14"x14" picture frame glass. Put a paper towel on top of that. The paper towel is really important because when you put your plate on that piece of protective glass, it's going to suck right down and stick and you'll screw up your emulsion getting it off.
Step 4: Position a tray/paper towel next to your enlarger; you'll use that to hold the drippy film when you're done exposing.
Step 5: Prepare for step #6 first, then flow a plate normally per your ambrotype process.
Step 6: Now, you're going to sensitize your plate in a tray instead of a dip-bath. You can use a dip-bath (I did that first) but it's awkward. Be stubborn or trust me, it's your call. To sensitize the plate in a tray I use an 8x10 tray with a couple of glass stirring rods rattling around in the bottom. It's crucial to have something in the bottom to keep your plate from sucking down to the bottom of the tray (and then to pick it up you've only got the edges, which means you're screwing up your emulsion). Get the tray set up, put the silver bath in it, then position your film near the tray. The way I do it is have one hand for silver and one hand for film. Silver hand is gloved, film hand is bare. Silver hand holds and manipulates the plate, film hand holds and positions the film. Immerse the plate in the tray, emulsion side up and start your time as per your ambrotype process. When the plate is sensitized, reach under it with your silver hand and pull it up, keeping the surface horizontal. What you're doing is allowing a bunch of the silver nitrate solution to stay puddled on the surface of the plate. Then take the film in your film hand and position it at one edge of the plate and slowly curve the film down so that it sucks down onto the plate from the capillary action of the silver solution. Don't allow bubbles to form between the film and the plate. What you're doing is using the thin layer of silver solution to eliminate the air/film boundary between the plate and the film. I tried this using water instead of silver solution and it didn't work at all. If you don't believe me, go ahead and try.
Step 7: Place the plate/film stack on the paper towel under the enlarger and expose. If you're familiar with traditional darkroom enlarging then you already know how to calculate the exposure time. If you're not, then: set the timer to 10 seconds and hold a black card over the plate so that just about an inch is visible. Expose 10 seconds then move the card another inch, repeat, etc. If you use a target covered with step-wedges like mine you can just pick the exposure that looks right. Bear in mind that this process is a direct positive process, so if you want areas to be brighter you're not doing like you'd do with film - with film you'd reduce the exposure, with a direct positive you increase it. So if your plate is dark or flat-looking double your exposure time and try again. If it's too burned out looking, halve it, etc. Or just use a test target with step wedges and get it right the first time.
Step 8: Gently and smoothly peel back your film by grabbing it by one of the "ears" at a corner and place it silver-nitrate side down on the paper towels you positioned near your enlarger. When you're done printing you'll want to clean that side of the film carefully without scraping or messing up the ink side.
Step 9 to completion: Develop and clear normally per your ambrotype process.
Test plate on 6"x8" black spectrum glass.
- Note that the corners do not have the usual holder-marks.
- The "curves" corrections laid out with the step-wedge and sample image, that allow me to determine which set-up I liked best. When I did my test plate I just emulated the curve that I liked and made a print with it.
- The divot in the collodion on the lower left is what happens when you pick a plate up from the tray of silver nitrate using your fingertips from the front. That's why I have spacers in the bottom of the tray, so I can reach under the plates instead.
- Pictorico film has a whitish look to it. This is microscopic pores on the "ink side" that are designed to allow the ink to bond. If you get the ink side wet you may notice that suddenly the film becomes beautifully clear and transparent. It also softens the ink. Keep the ink side dry and keep silver nitrate off of it! I did the experiment of soaking the Pictorico and doing a print and it makes no difference at all.
- The example print was washed in the manner described above and you can see a few blurs that were caused by water on the ink-side of the film - remember that a drop of water on the ink-side is like a miniature lens diffusing light before it can hit the plate. If you keep the silver nitrate always on the non-ink side of the film it will last indefinitely.
- The visible pixelation in the text is a result of the resolution of my computer's display, which is much lower-resolution than the ambrotype. ;)
This is a close-up if the grain texture of part of the plate:
By the time I was done monkeying around with it, my test target was pretty banged up. Most of the flaws are results of my wiping the test target, getting silver nitrate on it, etc.
I think this is a workable process and anyone who is interested in taking it to its logical conclusion ought to be able to refine it from here. The results are better than expected but not quite as good as direct lens-to-plate, as you'd expect. I do not believe that this process will allow credible duplication of an ambrotype (though perhaps newer generation Epson printers and Pictorico film might get even finer grains) but this might be an expressive creative medium in its own right.
I have asked a few artist friends to contribute digitally produced images that I can print with this process but, in truth, I'm not sure I care to pursue this process further; I got into doing ambrotypes because I like the results of direct lens-to-plate imaging and I have the tools I need to do it, so I doubt I'll bother with digital ambrotypes, much.
Eventually I plan to make an ambrotype of Lee Harvey Oswald with his rifle, to "prove" that he shot Lincoln.