Modifications to Kodak 8x10 hangers for even development of double-sided X-Ray film

[Sam L]

I've been working on developing Fuji HR-U double-sided x-ray film in 1-gallon vertical tanks with Kodak 4A hangers and have made some good improvements that I wanted to share.

I created a repeatable test that accentuates uneven development issues: I put 4 sheets of 8x10 film into film holders and then flash them each with a dim bare bulb for 1/10s. The resulting negatives are even but over-exposed. I then develop them in 1:250 510-pyro in vertical tanks using inert gas agitation with the standard 1s on 10s off pattern until the negatives are quite dense. The dilute pyro is unkind to uneven agitation (surge marks) and to insufficient agitation (bromide drag).

Here's the starting point with unmodified hangers:


I then increase the "dehaze" setting to +50 in Lightroom to really bring out any unevenness:


As you can see, the side and bottom edges have surging issues from the developer moving through the holes in the hanger. The top shows four white marks due to the hanger's springs touching the back side of the top. Here's an unmodified Kodak hanger for reference:


I did a bunch of experiments and ended up with three modifications:
1. Close the holes in the face
2. Cut open the bottom of the hanger
3. Raise the clip at the top so that it only touches the margin of the photo and extend the face so that it still holds the photo in.

Here's the result:


The surge marks on the edges are gone. The clip marks on top are gone. The evenness in the center is imperfect but unchanged. There remains some ghosting at the edges where the film sits in the hangers.

I'll follow up with details for each modification.

[Sam L]

Kodak 4A hangers have holes all the way around the sides facing out and holes on one of the faces. I thought the holes on the face were to improve chemical flow to the emulsion but the holes appear to be on the back -- the non-emulsion side of the film. Since HR-U x-ray film is double-sided, I thought it would make sense to drill matching holes in the other face of the hanger (left is unmodified, right has holes in both faces):


However, this made the surge marks much worse:


I additionally noticed that Carr hangers do not have holes in either the face. Taking the hint, I closed the holes in the face with a thin layer of epoxy (hot glue works too) and saw an immediate improvement:



The surge marks on the sides were gone. The bottom was improved, though some surge marks remained from the holes in the bottom edge.

[Sam L]

To fix the remaining surge marks at the bottom of the hanger, I used a cutoff wheel and a file to remove most of the metal in the bottom, creating long open slots:


The result was no more surge marks on the edges:


There is still more development at the margins (I'm guessing more turbulence from the hangers) but the lighter edges are much nicer than the surge marks from the pores.

[Jim Noel]

To fix the remaining surge marks at the bottom of the hanger, I used a cutoff wheel and a file to remove most of the metal in the bottom, creating long open slots:


The result was no more surge marks on the edges:


There is still more development at the margins (I'm guessing more turbulence from the hangers) but the lighter edges are much nicer than the surge marks from the pores.

Do you dip the hangers in Photo Flo? If so that is probably the cause of over-development along the edges. PF adheres to the metal and becomes a catalyst, thus over-development. Wash the hangers and use a toothbrush to scrub inside and out. Your problem should be solved if you keep them out of PF. I haven't used it since about 1970.
Jim

[Sam L]

No, I don't use photoflo. But, I will try scrubbing the hangers. Maybe they're contaminated from a past life or with other stuff. Thanks for the idea!

[Sam L]

The third change I made was to address the marks left on the rear emulsion by the clip at the top that holds the film in. It hangs down relatively far below what I consider the margin of the film. On single-sided film, this is a nice feature because the film is more secure from popping out during development. On double-sided film, this is a bummer because it's actually touching one of the emulsions.

This was a harder modification. I ended up removing the top clip and welding it back on a bit higher so that just the rod was below the edge of the film. Getting the clip off was not very hard. It's lightly spot welded on, so it was sufficient to grab the end of the rod in a vise and wiggle the hanger until it popped off. Getting it back on higher up is harder. I TIG welded it, which I imagine is not available to most people. Another option might be to tap the little dog that hangs down and bolt it back on, but this is challenging too. Modified hanger is on the left, unmodified on the right:


After the clip is moved up, it will only retain the film from coming out the back side. It might be possible to use the hangers like this but any sideways movement when shuttling the hangers between tanks could pop the film out the front, which is a disaster with the very tender x-ray film. My solution was to extend the front face down a bit with some stainless wire (left one):


The wire only hangs down as far as the clip and never touches the film during normal development. With this, the marks on top were gone:

[Neal Chaves]

I abandoned tanks and hangers for tray development in the 80s. I found that the hangers were acting like radiators around the edges of the film affecting developer temperature and activity, causing several types of artifacts.

[Sam L]

Neal, interesting idea about temperature being an issue. I develop at room temperature, but I pre-soak the hangers and negatives in tap water, which is much cooler to start. I wonder if that's causing some of the remaining edge effects I see.

[Neal Chaves]

Neal, interesting idea about temperature being an issue. I develop at room temperature, but I pre-soak the hangers and negatives in tap water, which is much cooler to start. I wonder if that's causing some of the remaining edge effects I see.

I never had a temperature-controlled tank line, just Cescolite plastic 4X5 tanks and Kodak hangers. I kept the lab at 68* in winter and 75* in warmer months.

[Vaughn]

Interesting project. I am wondering how just a wire frame with clips facing inwards from each corner to hold the film suspended within the frame would work in comparision. Creating a new style from scratch might be no more work than to modify existing hangers.

The sure cure is to photograph very busy scenes (such as forests) where a little unevenness does not show up in the image!