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

[schafphoto]

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/65535/52537440840_40403d0dff_c.jpg (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.
[url=https://flic.kr/p/2o3ti6e]https://live.staticflickr.com/65535/52536499947_f34ecc3c09_c.jpg (https://flic.kr/p/2o3y7Mw)

[url=https://flic.kr/p/2o3xaNH]https://live.staticflickr.com/65535/52537255889_c343d9dc52_c.jpg (https://flic.kr/p/2o3ti6e)

[url=https://flic.kr/p/2o3vFW9]https://live.staticflickr.com/65535/52536967016_14845b295e_c.jpg (https://flic.kr/p/2o3xaNH)

[url=https://flic.kr/p/2o3xaPE]https://live.staticflickr.com/65535/52537255944_5400c7bb29_c.jpg (https://flic.kr/p/2o3vFW9)

[url=https://flic.kr/p/2o3vFYt]https://live.staticflickr.com/65535/52536967151_63df95fc9b_c.jpg (https://flic.kr/p/2o3xaPE)[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,

[koraks]

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.

[nmp]

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.

[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.

[Tin Can]

Maybe use KODAK only hangers clipped to the dunk?

KODAK have more drain holes then any other

[AnalogAngler]

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.

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.

[ic-racer]

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.

[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.

[ASA1000]

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

[schafphoto]

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.

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/65535/52536967016_e8b0254112_k.jpg

[schafphoto]

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.

Thank you for the compliment. I'll add that the nitrogen-burst agitation in these 40-inch deep tanks is pretty aggressive at 8 second burst then 8 seconds pause. I did a lot of tests after having mottling in sky zones 7-8 that settled on those agitation numbers with HP-5. Except for this seemingly random intermittent flaw on thousands of sheets of film, the development seems perfect for my purposes in density and contrast and the rebate is clear so I'd rather chase a hardware flaw first before I tinker with development/agitation times.

And I have chosen samples that show the most extreme density change and not the ones where there is no density change.

[schafphoto]

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

36-40" tall stainless hangars.

[Tin Can]

First actual data on burst I have seen here in 12 years

I will try longer bubble time

[schafphoto]

To be clear, these clip marks are more typical of most of my film...

https://live.staticflickr.com/65535/49212314051_b4f3f7dc3c_b.jpg

https://live.staticflickr.com/65535/49754836941_c3cc379646_b.jpg

[schafphoto]

Just got a photo of the racks from the lab. They hold 10 sheets.

https://live.staticflickr.com/65535/52538301646_75eb3f8e3c_b.jpg

https://live.staticflickr.com/65535/52538850143_cf2689fce3_b.jpg

[Michael R]

That's the thing about gas burst. Assuming the right plenum/sparger design, bubble size, power etc. it can take experimentation to find the right burst duration and intervals, and it can vary with tank volume, film size, film type, type of hangers, how much space between hangers etc. Actually just recently I came across another paper/study published back when this was still a common process used in-house by a lot of organizations from military to scientific for developing films, plates etc. Very interesting stuff.

Unfortunately I'm not in a position to have such a system. Too complicated/inconvenient. On the other hand PE once commented gas burst should be down-scalable to any size as long as you test tune test tune test tune. He recalled even having seen tiny 35mm two-reel Kindermann tank-sized nitrogen burst someone had FABd up at Kodak.


First actual data on burst I have seen here in 12 years

I will try longer bubble time

[AnalogAngler]

Couple thoughts regarding chemical contamination:

1) As I recall (and pretty sure I found it on this forum - thanks go probably to Jim Noel and others) - the issue with the Photo-flo is that it is doing exactly what is is supposed to as a surfactant - helping to wet the film and specifically the emulsion - so that chemicals move on or off them smoothly. As a result, the areas that recieve even just a little bit of surfactant (and it generally takes very little surfactant to do anything - it naturally spreads out to be a molecularly-thin layer) are subsequently exposed to developer a little faster/longer than the rest of the film resulting in increased activity and density. There are probably more elegant explainations - I would seek them out by searching the forum if you think you need more detail.

2) Two thoughts on the clips and occasional nature of the problem:
a) The design of the clip (with a hinge and a spring) includ additional surface area and may even allow a droplet to be captured inside the clip only to dry up later (or even stay wet) - but might not happen or to the same degree all the time.
b) The lowest clips on the rack might have more residual chemical at the end than the upper clips as everything is draining down the long rack as it is pulled out of the bath and dried (believe they are displayed sideways in the photos - with the longer pin end at the top in normal use) So film installed in the lower positions may be more prone to this effect.

In either case - if they are not washed between runs, this may give the Photo-flo or similar agents a chance to dry and concentrate in these locations, only to be re-animated when re-wetted at the start of the next run - with the film already in them. Based on my experience with the 120 reels - it doesn't necesarily even have to be trapped, just the amount left coating the surface of the metal was enough to influence density, and there is more surface area inside those clips than anywhere else in the set up they are using.

Since your lab provided photos, it sounds like you have a good relationship with them - did you send them photos of the issues/your concerns and if so did they respond?

I can see that they would be hesitant to add an additional cleaning step as the machine puts out a dry rack on the end, and solving this may mean having to wash down and dry the rack outside of the machine between each run. It could also be that the machine was designed this way and functioning normally, and normally this is not an issue, but maybe someone was a little heavy-handed with the Photo-flo or something else on a given day and the problem doesn't show up until later. Batch numbers could be important here. At any rate, I would trust the lab to know more about what is going on with the chemistry than I do...and also hope they provide some constructive feedback.

Best wishes & regards,

-AnalogAngler

[ASA1000]

233255
I commented on this the other day and just came across this today in a 1973 Kodak technical publication233256
The images are upright on my computer!

[Bernard_L]

Several comments suggest a process having to do with "film & developer & process combinations".
What I did observe on a couple of occasions with 35mm/MF film is that mechanical stressing or creasing (problematic loading in spiral) produces local excess density in the developed film. So nothing related with development.

[koraks]

Several comments suggest a process having to do with "film & developer & process combinations".
What I did observe on a couple of occasions with 35mm/MF film is that mechanical stressing or creasing (problematic loading in spiral) produces local excess density in the developed film. So nothing related with development.
I think many of us have seen that, I certainly have. And it's always clearly recognizable from the geometry of such density anomalies - i.e. the typical crescents and kinks that result from the physical cause of the problem. Unlike in this case, where such a physical/geometrical pattern is not present.

[Tin Can]

Calumet offered in their catalogs, various gas burst schemes

For color, which I never do they had plastic 'screens' on 2 sides of sheet film

Lines of tanks, aka Tank Line in many sizes

I use three 1 gallon Calumet SS covered with adjustable plenum tanks in a bigger tank for temp control all sitting in a new cheap laundry sink

I find it relaxing as they bubble

[Bernard_L]

I think many of us have seen that, I certainly have. And it's always clearly recognizable from the geometry of such density anomalies - i.e. the typical crescents and kinks that result from the physical cause of the problem. Unlike in this case, where such a physical/geometrical pattern is not present.

Sure. But my point was not that the over-dense regions (appearing as light in the positive)
233265
were due--specifically-- to kinks during loading or other, but rather, more generally, caused by mechanical stresses as might be caused by a (misaligned?) film clamp.

[LabRat]

It's a local agitation issue around the clips, where the bubble burst over the sheet area allows the bubbles to flow upwards, but this is impeded by the clip area... The sign is there is clearer or denser areas around clips where the "clouds" of developing by-products are not being displaced by the bubbles... The "clouds" contain by-products that can increase or decrease developing activity significantly and not being displaced/dissipated back into the solution efficiently...

Changing the style of clip to the older triangular tip that has the single bump to hold film would allow more flow through clips, or at one of my old E6 labs that used gas burst had to physically lift a rack at least once during the shorter E6 process to clear the sheet of by-products or risk uneven development... Most labs eventually went with true "dip & dunk" machines that raised the racks clear of the solutions during cycles to fully drain sheets of "clouds"... This is true with most dip hanger systems, and it also much helps to tilt hangers past 45° also for a sufficient "dwell" time to drain edges of hangers better...

Steve K

[schafphoto]

The clips do seem pretty opaque (from a liquid perspective) and i was thinking that drilling a through-hole in each clip would improve drainage and maybe the tendency to hold chems. Just a thought. More likely than welding improved clips on a valuable and rare stainless Refrema rack.

[LabRat]

But it's probably that the clips form a "shadow" from where the bubbles flow, and not getting proper clearing of the "clouds" in the clip area...


Try lifting/tilting racks during process to completely drain sheets before re-immersion a few times during dev step...

Steve K

[ASA1000]

But it's probably that the clips form a "shadow" from where the bubbles flow, and not getting proper clearing of the "clouds" in the clip area...


Try lifting/tilting racks during process to completely drain sheets before re-immersion a few times during dev step...

Steve K

It's not a shadow, it's chemical contamination. Read the excerpt from the Kodak technical publication I posted here. and Merry Christmas!!

[LabRat]

It's not a shadow, it's chemical contamination. Read the excerpt from the Kodak technical publication I posted here. and Merry Christmas!!

As in turbulence eddy...

The sign it's agitation is that the development by-products can leave denser and thinner streaks/blobs in less than ideal agitation areas due to improper agitation... It is local to the clips, enough for the "clouds" to congregate near as bubbles will flow around clips, with a "boundary layer" holding clouds and diverting flow around obstructions...

This used to happen in the E6 gas burst line labs, usually leaving a greenish blob around where they clip...

Steve K

[Mick Fagan]

I'm in agreement with Steve K (LabRat), the occurrence is the same from one side of the rack to other in each case. The shape of the issue is nearly identical and is in a consistent manner in multiple sheets. With one side being one shape, while the opposite side is the other shape.

If indeed it was chemicals being left on the clips after going through the process, then in some instances the amount of retained chemistry would more than likely be of a different shape from different runs through the bath on different films.

Around 32 years ago I left working in a professional lab where I had quite a bit of exposure to Dip "N" Dunk E6 and C41 with gas burst agitation and the sometimes many issues in development unevenness due to gas flow. Other times things worked brilliantly, but sometimes....

I also don't remember cleaning our racks, except when we dropped a bath, whether it was the E6 or C41 bath. We could sometimes put shed loads of film through on some days.

[ASA1000]

I'd start by showing him the information I posted from the Kodak Technical Bulletin. I do think contamination might be affected by gas too.

[schafphoto]

So film installed in the lower positions may be more prone to this effect.
-AnalogAngler

That's one of the things I was going to experiment with. Top of rack vs. bottom of rack occurrence. The top of the rack sheets are out of submersion in developer for longer than the bottom sheets when the rack is lifted 36 inches out of the developer tank and lowered into the stop tank.

[Neal Chaves]

I suggest that the increased density of the negative in those areas is due to the compression of the clips on the emulsion.

[schafphoto]

I suggest that the increased density of the negative in those areas is due to the compression of the clips on the emulsion.

Perhaps, but compression seems unlikely since after decades of similar clips being used on Refrema and Sitte-Tischer racks, I would think it would have been engineered out of the system by now if compression, kinking or impact damage was the cause. I'd ask you how does clip compression effect film density exactly?

[schafphoto]

233255
I commented on this the other day and just came across this today in a 1973 Kodak technical publication233256
The images are upright on my computer!

Thanks ASA1000.

For future readers of this thread, the Kodak publication mentioned and excerpted by ASA1000 is available as a complete PDF in a few places on the web in December 2022.
Try searching "Kodak J-1 Processing chemicals and formulas for black and white photography" and you should find links to PDF's of the entire publication.

[Neal Chaves]

Increased density in the area of a clip would depend on the emulsion type. Some may allow more spread through the emulsion than others just as some film types are more prone to “light piping” through the film base than others.