Autoradiographic plates

Outdated medical technology isn’t normally the kind of thing I’d be interested in, or would write about – but I was given some old glass autoradiographic stripping plates. I didn’t know what they were at the time – I assumed they were normal photographic plates, but I’ve done a little light reading.

Autoradiography

The gist of autoradiography is that you:

  • inject a creature with a radioactive chemical
  • allow the radioactive blood to be pumped around its body
  • kill it
  • cut it into thin slices
  • stick the slices onto an autoradiographic plate
  • leave the radioactive slices stuck on the plate for days or weeks while the image forms – in effect a contact print but the “illumination” is provided by the sample itself, rather than an external light source
  • develop the plate in the same way as normal photographic prints

I found the following account in the Journal of Anatomy, 1978:

The investigation was carried out on 10 days old rats. Of the 11 animals used one served as a control and the rest were each injected intraperitoneally with a single dose of tritiated thymidine (2 μCi/100 g of body weight). The rats were killed by decapitation either 2, 12 or 48 hours after injection. The knee specimens were collected, fixed in absolute alcohol for 48 hours and then washed in distilled water. Cryostat sections 7-8 μm thick were cut and mounted on glass slides coated with a thin layer of gelatin. The sections were then stored in an oven at 37 °C.

J. Anat. (1978), 126, 3, pp. 547-554

The article continues to describe how the plates are developed and treated afterwards, which seems fairly typical of any printing done in a darkroom.

This is all good and well, but I have no intention of force-feeding a rodent some Red Bull and then cutting its head off. I’ve hardly been able to find any data about these particular plates – marked as Kodak AR.10. However, both the leaflet with the plates and the previously referenced article mention using a dark red safelight, which implies that the plates are indeed sensitive to visible light as well as X-rays and γ-rays.

Sensitivity to visible light sounds much more useful to me.

Making my own contact prints

As I had a box of 12 I thought it might be fun to try making some prints. And as they were free (saved from the bin!) there’d be nothing lost even if they’d expired or if I ruined them. The plates are 4¾ × 6½ inches, which is a nice size for a novelty glass print (I think).

I started off trying to make a simple contact print, by placing a heart-shaped pad of post-it notes on the plate and exposing under the 60W bathroom light for one minute. I then developed in Ilford ID11 for five minutes, diluted 1:1 with water. I washed the plate in stop bath for one minute and fixed in Ilford Rapid Fixer for two minutes.

The plates certainly hadn’t expired, as the area exposed to the light was black, and the area under the post-it pad was clear. However, the outline of the pad was extremely blurred to the point where it wasn’t possible to tell what it was. I think this was worsened as I had accidentally had the plate upside-down, with the emulsion on the opposite side of the glass to the pad.

I tried again, this time with the emulsion face up. The result was hardly any better. I was disappointed, since if I couldn’t make a simple contact print of a white heart on a black background, the chances of doing anything else successfully were slim at best.

Building an enlarger

My original plan, if the simple contact prints had been successful, was to make some more contact prints of some 6×9 cm 120-format negatives on the plates. They would certainly look unusual. Having failed at any sort of contact print, I wondered if it would be possible to project an image onto the plate.

I don’t have an enlarger or a project, but I do have some very crude cameras that I thought might work in reverse. Using a 1929 Voigtländer Bessa folding camera, a porridge box and a light bulb, I managed to project a 120-format negative onto my wall in a dark room. As you can see, I’ve placed a book on top of the box to keep it still, and propped up the nose of the camera with a smaller box. You can also see the silver shutter release cable. Finally, I draped a black T-shirt over the entire arrangement, allowing just the nose of the camera to protrude, because it was leaking light quite awfully.

My homemade enlarger

The image of the 120 negative was reasonably sharp, but at the camera’s closest focusing distance of four feet, the image stood some 18 inches tall. For too large for a 6″ plate. After a bit of tinkering with some card and I managed to make a holder for a strip of 35mm negatives. When projected, these produced images that were still somewhat larger than the plates, but I thought it would be OK to “crop” them and represent only the central area of the negative on the plate.

Making the image

Given that one minute under a normal bathroom light had produced roughly the right exposure, I reasoned four minutes using a 40W bulb in my enlarger (significantly dimmer) would probably be OK.

After exposure, I processed the plate the same way I had done before. But this time, success! Here’s my finished plate – a picture of my brother riding his bike. (You can see the original image on my photo blog).

My finished plate

Given that the grain is kind of awful, I would guess that the exposure time was too short and the development time was too long. I still have plenty of plates remaining, so I will try more like this after I’ve selected some more of my negatives from the archives. I will probably try exposing for ten minutes and developing for three.

I don’t know about you, but I think this retro-looking plate is incredibly cool. Anyone can do anything with a DSLR and Photoshop, but I think it’s more fun to play with expired X-ray plates and cameras from before my grandparents were born :)

  1. Lancaster Instantograph | Jonathan Gazeley - pingback on December 26, 2012 at 6:30 pm

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