Why does my film BOW after drying???

L

LeicaVirgin1

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Dear Tom-

Thanks for reading this... My question is... Why does my film BOW after I let it hang and dry. It does not curl; it BOWS... Like curves inward; like the inside of a ahallow bowl. A pro skateboarder would love some of the films I develop & dry!

I notice that this happens with all Kodak, Fuji, AGFA, & Fuji Films... (B&W of course).... The only one that does not do it, (at least in my experience), is Ilford HP5+.... It dry's straight... I like Tri-X & want to use Tri-X... because it is very forgiving, (except this darn BOWING action.)

Any explanation, or advise?

Best,

LV1
 
Its caused by lack of humidity in the air. My kodak films dry flat or very bowed depending on the humidity. In summer and spring it is very rainy and humid in the part of the USA I live in, and my films dry flat. In winter the air is dryer and they dry with a horrid lateral curl that takes several weeks of flattening under a stack of HEAVY books to remove so that I can scan them. The film also dries very fast right now because of the low humidity in the air, while in summer it can take as long as 2 hours to dry. In winter, 20 minutes and its done! I think drying too quickly causes the curl.
 
Here in Canada the humidity is next to zero in the winter and I get the bowed film too... best thing to do is wait till it dries, then roll it backwards against the bow (shiny side in) and put it back into a film canister overnight... by the next day the film is almost flat (and I use betterscanning glass holders to get it perfectly flat in the scanner)
 
the temp of your final rinse plays a roll too. if you go from a relatively cold rinse to a dry, warm place to hang you better get out the old textbooks to flatten those things out.
 
I live in Utah, which is bone-dry all year round, and I've learned to select my film partially for which ones curl inward when drying and which don't, at least in 120. Tri-X, Fomapan 100, and Neopan 400 dry flat, while HP5 and Acros curl, and that stock of Rollei Retro 100 that has been going around is just ridiculous in how much it curls.

In 35mm, most films curl for me at least somewhat, but Fomapan 400 dries completely flat.
 
Interesting. The 120 Acros I've developed dry perfectly flat. Much more so than anything else I've used, including Fomapan 100 & 400.
 
It depends on the base of the film. APX 100/400 curls sufficiently to be used as buggy springs! Arista 400 is bad for the "bow" but will flatten out after a while. Tri X is not too bad, some curl - but just putting it in file pages helps straighten it out.
Kodak's XX movie stock dries completely flat - irrespective of humidity.
I do cut "bowed" films and stick in file pages and stack a couple of books on top of them - the big Magnum book can flatten the most stubborn film overnight - and I fervently hop that the film underneath picks up some hints from the book too.
 
With the exception of really thin film stocks (e.g. Lucky 100, Shanghai GP3, and Foma 100, 200, and 400, all in 120; the 35mm stocks aren't bad), I don't find film curling to be a big problem. Let the film curl. Be sure to use a heavy weight on the bottom of the roll while drying to keep the curl reasonable (I use the Paterson clips because I like them so much; I find myself opportunistically buying a couple of pairs of them anytime I'm in a photo store and see them in stock).

I store my negatives in archival plastic negative sheets in binders, and find that after a few weeks or months, the curl has disappeared. I processed a bunch of film in December, and when printing yesterday, the only rolls that had any curl of significance remaining were my Chinese and Foma 120 rolls, which were still rather annoying, but that binder isn't very full yet. (Serves me right for shooting budget film 🙂 ... but they're interesting films. Kodak, Fuji and Ilford are a lot better behaved.)

I find that even when my thicker 120 films, or any 35mm films, are still fresh (i.e. processed recently and still curly) that the enlarger negative holder holds the film flat and it's not a problem.

I'm not as experienced a worker as Tom but I have done this since the '80s... and I vote for patience. No particular effort is needed to solve this problem, except patience, weights on the bottom while drying, and good storage.
 
Tom A said:
I do cut "bowed" films and stick in file pages and stack a couple of books on top of them - the big Magnum book can flatten the most stubborn film overnight - and I fervently hope that the film underneath picks up some hints from the book too.
Click to expand...

Photography by osmosis - what a brilliant idea 😀
 
PhotoJim said:
With the exception of really thin film stocks (e.g. Lucky 100, Shanghai GP3, and Foma 100, 200, and 400, all in 120; the 35mm stocks aren't bad), I don't find film curling to be a big problem. Let the film curl. Be sure to use a heavy weight on the bottom of the roll while drying to keep the curl reasonable (I use the Paterson clips because I like them so much; I find myself opportunistically buying a couple of pairs of them anytime I'm in a photo store and see them in stock).

I store my negatives in archival plastic negative sheets in binders, and find that after a few weeks or months, the curl has disappeared. I processed a bunch of film in December, and when printing yesterday, the only rolls that had any curl of significance remaining were my Chinese and Foma 120 rolls, which were still rather annoying, but that binder isn't very full yet. (Serves me right for shooting budget film 🙂 ... but they're interesting films. Kodak, Fuji and Ilford are a lot better behaved.)

I find that even when my thicker 120 films, or any 35mm films, are still fresh (i.e. processed recently and still curly) that the enlarger negative holder holds the film flat and it's not a problem.

I'm not as experienced a worker as Tom but I have done this since the '80s... and I vote for patience. No particular effort is needed to solve this problem, except patience, weights on the bottom while drying, and good storage.
Click to expand...
I've had the reverse experience with the cheap films , they always dry flat, my tri-x and other kodak films are ridiculous with the curling . Ilford stuff seems to dry pretty flat as well.
 
The reason film curls is that it is actually several layers of material. Nylon substrate on one side, highly refined gelatin holding silver salts on the other. When it is very dry, or very humid, the two "sides" retain water at different levels and one side is swelled compared to the other. Kind of like a "spring" style thermometer (think old analogue home thermostat or an oven thermometer). These are two types of metal with different heat expansion properties fused into a strip and then coiled. When the temperature changes, the spring coils more tightly or more loosely because one type of metal is expanding more than the other. Imperfect analogy, but same idea.

Ben Marks
 
I just moved to Arizona for a few months and I had the same problem when i got here. I went to target and bought a 30 dollar humidifier, cranked it in the room with the door shut for like an hour or so and then put the negs under a book or two. They flattened out within the hour without the book, but I used the book for good measure.
 
speed IMO. The faster they dry, the more of a curvature there is across the short side of the film. I get a winter summer variation and find that drying in a bathroom after a shower helps as the film dries more slowly due to the humid air. I guess it is humidity AND speed as they are related, but I have found that when mine dries in the cold dry air of winter, there is no problem as it takes 2-4 hours at 14 degs C or so in my bathroom.
 
There's simple cure - after drying I roll film emulsion out (about 8-10cm diameter) and after 8 hours swap ends (inner becomes outer) and leave film for next 8 hours. 7or 10 doesn't matter really. I prefer this to pressing. In fact, this method gives me flattest negs I have seen.

I learned this trick in local minilab, they developed my B&W film before I started my own development. So they lost me as customer in this segment, but I continue to buy chemicals, paper and lens caps/batteries and order color prints there.
 
btgc said:
There's simple cure - after drying I roll film emulsion out (about 8-10cm diameter) and after 8 hours swap ends (inner becomes outer) and leave film for next 8 hours. 7or 10 doesn't matter really. I prefer this to pressing. In fact, this method gives me flattest negs I have seen.
Click to expand...


I do not understand what you mean. You dry them hanging on clips??
If so do you turn them in the clips?
Could you please explain?

Thanks!
 
J. Borger said:
I do not understand what you mean.
Click to expand...

Sorry - English is not my native language. After film has dried, I take it off clips, cut ends and spool whole film into roll with emulsion out, diameter of roll is about 10cm (not too small, not too large) and put away from sun and dust (I have empty plastic can of similar size with matching cap, but you can put it in paper bag or large envelope).
 
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