At long last we've started to hit pay dirt. This is a test exposure from the 8x10 pinhole camera which, although it reveals a few issues mostly related to handling sheets of the x-ray film I used, shows that we're really in business now.
What we're looking at is from a scan of a contact print made on Ilford Multigrade RC paper using a make-shift contact printing frame that consisted of a piece of 11x14 picture frame glass, taped along the edges and laid over a left-over sheet of the black felt used in the build. The long white scratch towards the top middle is actually a scratch in the glass I didn't notice at first or I would have chosen a different piece. The black mark in the lower right corner is a fingerprint. Though I handle the unprocessed film with surgical gloves I was having a time of it getting the exposed sheet out of the film holder that way and taking off the glove seemed less risky than continuing to struggle glove on and risking even more damage.
I knew going in that developing the film would be a challenge. Unlike more conventional film if the surface of the unprocessed emulsion is touched it will be permanently visible in the developed negative. To make matters worse the emulsion is coated on both sides front and back so there's no part that's safe to touch. Further, the emulsion is soft, especially when wet, and scratches (both sides) very easily in the development process. At nearly 1/10th the price of conventional 8x10 film though I'm willing to put up with a few challenges. It even has the advantage of being okay to handle under safelights. Handling film in total darkness has become so instinctive that I found I had to keep reminding myself that it was okay.
The preferred method of processing sheets of x-ray film is to put them in stainless steal hangers and processing in vertical tanks. These are hard to find these days and can be a fairly expensive proposition. The most popular way to process large format film generally is to use trays and develop them in much the same way print on photo paper are processed. With delicate x-ray emulsions however it's a virtual guarantee this will result in scratches, mainly from the ridges found in conventional processing trays. Some x-ray film users get around this by using flat-bottomed trays. The ridges are there for a reason though; it's easy for sheets of paper or film to get stuck to the bottom and with no way to work your fingers underneath you may have a time of it getting them out.
In the various forums where thing like photography using x-ray film is discussed I had heard of another method, processing in zippered freezer bags. A sheet of 8x10 film fits just right in a standard large size freezer bag. You can pour chemicals in, zip the top up and do almost anything you want with the sealed bag. I decided to try this. Unfortunately none of the people who mentioned this method went into much detail about how to implement it.
So began the learning curve. For my test shots I drove down the road to the International Railway Bridge between Fort Erie and Buffalo NY and made two exposures. I actually got three negatives as I had accidentally loaded one side with two sheet stuck together and the film is actually transparent enough that there was an image on the sheet underneath. This method requires processing one sheet at a time and I had three to practice with. I spent the first two (the two that were stacked) to learn that having a separate bag for developer stop and fix was not the way to go. The third image, this one, was processed by putting the film into a dry bag, filling it with developer which I poured out into the developer tray when finished, pouring the stop bath into the same bag and dumping it into the stop tray when finished and so on. After fixing I simply filled the bag with wash water, let it sit a few minutes with a bit of agitation and going through several changes of water like this before hanging to dry. This has the added benefit of washing the interior of the bag. I figure each one should be good for a few sheets of film.
I believe the major weakness with this method is visible in the odd density variation seen towards the lower left. Getting the bag closed after pouring a new liquid in can be a challenge. I got the kind that you can feel teeth meshing to confirm you have a good seal, but it can sometimes take a few tries under dim red lights to get both sides lined up properly and all the while the film is sitting only partially submerged in the chemistry. It also tends to float up and get in the way of closure so the operation is further complicated by the need to hold it down. I think what happened here is that the film was too close to the seal and even though it wasn't in the way of the seal it got pinched up there limiting the flow of developer around it. I found it useful to use only enough chemistry to keep the film easily submerged once the bag was laid on its side - about 500-600 mL. More than this made it harder to close the bag and increased the tendency of the film to float up. With a bit of experience I might be able to get reliable results with this method. If not I'll try something else. With a bit of luck maybe the chance to get my hands on some 8x10 film holders may come along.
A final note, getting back to the camera itself, I have given it one of the updates I talked about before. While making the test shot went fairly smoothly it was evident the camera would benefit from a better plan for the shutter than to literally use my hat so this was priority number one.
The idea of keeping the pinhole covered with a simple magnetic sheet, the kind typically used for refrigerator magnets, is so simple I can't believe I hadn't run across it before. All that's needed is a steel washer surrounding the pinhole opening. I thought I would need to replace the aluminium one I had used before this plan occurred to me, but a serendipitous find in one of my boxes of odds and ends turned up a large convexly curved steel washer that fit right over the existing setup. I epoxied everything in place since I didn't want screw heads jutting above the surface and even the large washer seems too thin to counter-sink. I have a large sheet of this magnetic material with peel away adhesive backing, left over surplus from the old family business, that I used to make the custom magnet in the above photo, but just about any old fridge magnet would do for this. They have enough hold to keep the pinhole securely covered until everything is ready to make the exposure but not so much to worry about jarring the camera when it is pulled away to start the exposure. To end the exposure simply slap it back in place. What could be simpler?
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