Quote Originally Posted by oldfaithful58 View Post
The relative humidity of the air in the room when drying the film needs to be as near as possible to 50%. In winter in Finland, the dry air brought into the house and warmed up to 20c has a relative humidity of 20 to 25%. The film curls like hell.
For me, 'curling like hell' means a roll of 35mm Tri-X cups around the entire length of the film a good 120-150 degrees, almost half a circle. Not as extreme as the attached picture, but really close.

In storage it takes my negatives about a month to flatten to the point that I can put them in a scanner and scan them. The enlarger is obviously better since the neg carrier flattens them nicely, but sometimes they can be tough to align without somehow damaging them.