Change of density at film hanging clips on dip-dunk processing

See samples for the density change I am seeing at the hanger-clips. It doesn't happen on all sheets of film.

Ilford HP-5 film. Developer: Clayton C-76 in a Refrema dip and dunk machine. Typical development times like the Hangar photo are 7 to 8 minutes, Canal aerial below was a 14 minute push.

https://live.staticflickr.com/65535/...403d0dff_c.jpg[url=https://flic.kr/p/2o3y7Mw]

This aerial was loaded from the left side resulting in a sheet that went on the rack upside down, same problem.
https://live.staticflickr.com/65535/...4ecc3c09_c.jpg[url=https://flic.kr/p/2o3ti6e]

https://live.staticflickr.com/65535/...43d9dc52_c.jpg[url=https://flic.kr/p/2o3xaNH]

https://live.staticflickr.com/65535/...845b295e_c.jpg[url=https://flic.kr/p/2o3vFW9]

https://live.staticflickr.com/65535/...00c7bb29_c.jpg[url=https://flic.kr/p/2o3xaPE]

https://live.staticflickr.com/65535/...df95fc9b_c.jpg[url=https://flic.kr/p/2o3vFYt]

Since it doesn't minimize the documentary value of the negatives it I have been able to work with this problem, but I sure would like to know if someone has a solution. I must deliver uncropped images with the rebate edge in the scan so the obvious solution of shooting wider and cropping is not available to me.
Thanks in advance,

My first thought would be to look in the direction of film & developer & process combinations. Did you notice any particular combination being more prone to this issue?

In principle, you could try to vary any of these three parameters. I.e. try a different film, try a different processing regime such as trays or Expert drums (may not be viable for workload considerations, I presume) or try a different developer (which is probably a non-starter in your present dip & dunk service). Since the film seems to be the parameter that is the easiest to change, I'd start with that and see if the problem goes away.

It's a tricky one, though; the problem with sheet film is that anything that touches the emulsion or the edge of the film is likely to have an influence on local density, in my experience. I myself stick mostly to tray development for this reason. But that's a labor-intensive approach that probably won't work for you in any considerable film volume.

Seems like the clips are distorting the film enough to cause some preferential development (due to turbulence) in those areas, increasing the silver density in the vicinity. Are there other clip designs that can keep the film planarity intact - may be those that hang the negative from the top edge along the rebate without what looks like spikes in these pictures.

Makes me wonder about the hanger clips. Are they holding chemicals between baths? Maybe the frame type hangers that dont clip the film will do better.

Maybe use KODAK only hangers clipped to the dunk?

KODAK have more drain holes then any other

Quote:

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Originally Posted by Gary Beasley

Makes me wonder about the hanger clips. Are they holding chemicals between baths? Maybe the frame type hangers that dont clip the film will do better.

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I wondered the same - I saw a similar effect with 120 reels showing extra density near the edges and believe it was from trace amounts of Photo Flo left over from previous run. I now wash them between runs and the issue has gone away.

There are a few articles in the X-ray film literature on exhaustion causing un-even development. The thought being it is not the extra activity near the clips causing the issue, but lack of development on the rest of the image.

I guess if you can't solve it, use a wider lens and crop. Too bad those are beautiful images.

I have answered questions about this problem many times. It was a common one when I started at the college (now retired). Without gong into the detailed background, the hangers are contaminated, probably with the remnants of Photo-Flo. Run them through the dishwasher w/o detergent OR using very hot water, scrub them with a stiff toothbrush, then rinse in fresh almost boiling water.

Hangars contaminated is my guess as well. No one has asked if these are plastic or stainless hangars, plastic might be worst!

Quote:

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Originally Posted by Jim Noel

I have answered questions about this problem many times. It was a common one when I started at the college (now retired). Without gong into the detailed background, the hangers are contaminated, probably with the remnants of Photo-Flo. Run them through the dishwasher w/o detergent OR using very hot water, scrub them with a stiff toothbrush, then rinse in fresh almost boiling water.

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I was thinking it might be a chemical crossover from the previous run, but since the result was mostly added density and not reduced density I couldn't see how that would happen. The rack (holds 8 sheets of film, I think) comes out of the machine dry, and then the rack hangs around a few minutes and gets run again or it could sit for a week before it gets used again for another 4x5 run.

I'll try to get a photo of the rack and find out exactly what chems are in the last baths.

So I can have an intelligent conversation with the owner of the lab, help me understand what's happening with leftover PhotoFlo (or stabilizer) that would introduce a localized area of altered development. I can see both stimulated development on the "inside" side of the clip and reduced development "outside" the left clip towards the edge of the film on this and other negatives.

https://live.staticflickr.com/65535/...b0254112_k.jpg