Film Drying

How do labs get film to dry so flat?

When I hang mine with clips from a shower rod, it tends to want to curl. Is it having a film drying cabinet, temperature, or something in the washing.

Thanks,
Bill

I assume you're talking about small-format (roll) film, since I've never heard of this problem with LF.

Curl on which axis, like trying to re-spool into the cartridge, or trying to turn into a long straw?

The former is usually corrected by using a weighted clip on the bottom when hung to dry.
Film clips are commonly sold in pairs, with one weighted and one unweighted.

I've had the latter happen with many rolls of 35mm film. It doesn't seem to matter how they were dried.

- Leigh

I have had o problem with sheet film, but certain 120 roll films have really been a problem. Efke 120 films have probably been the worst, I think they have a built in curl. I hang them with a weighted clip to dry, they still curl. After sleeving them, I put the sleeved strips into a reverse curl in a toilet paper roll for a few days. It at least gives me a chance toscan them before they revert to their perverse curl.

For me, Tri-X 35mm dries with a longitudinal curl, and HP5+ does not, even when developed in the same tank and dried the same place. So the film has a lot to do with it. My sheet films sometimes come out with a slight curl but it doesn't bother me. It's probably the same radius as whatever it was on the master roll.

I experience mostly with roll film, but also with sheets, much less frequently, and it's usually self correcting (e.g. it eventually dries flat).

Apparently humidity, and temperature, as well as the temperature of the final rinse or wash all can play a role.

If the air is too dry, or the temperature too high, causing film to dry too quickly,

or if there's a huge difference in ambient temp and temp of final wash.

I guess there are some variables that need to be considered that a drying cabinet can take care of?


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Quote:

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Originally Posted by spacegoose

If the air is too dry, or the temperature too high, causing film to dry too quickly,
or if there's a huge difference in ambient temp and temp of final wash.

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Good possibilities. I've never had a problem with sheet film, which always dries flat.

I have a thin rod running under the front edge of the shelf above the sink.
The sheet film hangers go on that rod and dry in room air, usually overnight.
Humidity is probably rather high since the darkroom has been in use, including water rinse.

In contrast, 35mm rolls from the early 60s, cut and stored in archival pages, show significant lengthwise curl.

- Leigh

For 6x12 rollfilm I use a Senrac dryer without heat. No problems.

I hang roll film from regular wooden spring-type clothespins, each of which hangs from a string stretched across the width of my drying closet. Each clothes pin has a small hole drilled in each handle and the string runs through these holes. I clip the same type clothespin to the bottom edge of the film strip as soon as it's hung. Normally, air dry at ambient temperature, but if I need a fast dry, I can warm the closet with a small space heater. When cut into short strips and stored in buffered rag paper, I have no curling problem at all, at least with Ilford Films.

---Harry K.