Film curls... help!

[rippo]

Randy: I live in Southern California, and we've outlawed humidity of any sort around here. Very dry, almost all the time!

desi8888: If I were printing with an enlarger, this curl wouldn't be a problem. Every enlarger I've used smashed the film nicely flat. But scanning is a different story. Curl can result in image distortion, as one dimension gets shortened but not the other (and in a nonlinear way). And worse, with too much curve the negative actually touches the glass, which results in newton rings appearing in the scan.

Fortunately, the reverse-coil on the reels has helped greatly. I do find that the film will start to curl quickly after being pulled off the reels, so I don't leave it sitting around before scanning. But so far I haven't had any problems like I did in the past.

 

[Worker 11811]

Which way is the film curving?

If you lay the film emulsion side up on the table, the edges should come slightly off the table. If the film is "positively curled" like this, dry the film out.

If you lay the film on the table, emulsion side up, and the edges curl down, leaving the middle above the table top, it is "negatively curled." In this case add humidity to the film.

The best way to humidify film is to make a humidity chamber. Seal the film inside an airtight, plastic container like a Tupperware bowl along with a wet sponge. Make sure that the film doesn't come into direct contact with the water. You want to humidify it, not soak it.
Leave the film in the container overnight and check it the next day. Monitor its curl and take the film out when it looks the way you want it to be.

If you overdo it, just leave the film out to dry. It should go back to the way it was before you started, eventually.

 

[Q.G.]

I found that nothing more than breathing on the film did the trick.

 

[desi8888]

so if I'm using a leitz focomat that has a negative carrier that presses down on the negative, curl is not an issue?

 

[Q.G.]

Shouldn't be, no.

Only getting the film in the right spot in the holder will be a little bit more difficult, since it will only get there (in the right position) after the holder is shut, pressing the film flat.