An irritating quirk of Fuji and Kodak films

sparrow6224

sparrow6224

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Hi Tom and all --
I don't know that this is the right forum but I thought Tom would have some good ideas on the problem: why is it that Ilford films (specifically Pan F and HP5+), which I don't love that much, stay beautifully flat when drying and after, but the Fuji and Kodak films that I much prefer arch in the middle and curl in at the edges, making them far more difficult and inconsistent in the scanning. Huh? How come? Huh? Huh? It really annoys me.

Vince P
 
Vince. it has to do with the "backing' - the strip that holds the emulsion. Some manufacturers use a film that will stay flat (Ilford among them - and the movie stock XX from Kodak). They will settle after a while - I usually file them in the pages and leave them overnight under some heavy books and that usually settles them down.
Even though you hang them up to dry - the film is still "green" - it has some residual moisture in it and that also causes it to curl.
Some films are really bad for it - Lucky 400 can be used as a mainspring for a grandfather clock! It takes quite a while to go flat.
There used to be a "film flattening" solution from Kodak - I never tried it as i prefer not to add more stuff to fragile emulsions if it can be avoided.
If you allow the film to hang up and dry for at least 8-12 hours - it helps a bit and also use substantial weights at the bottom of the film while it is hanging - that takes the long curl out. The film has been spooled up in a cartridge, the wound through the camera and in the end rolled up on a developing reel - so it is used to being curled up.
The other thing is that if you are using 100ft or 400ft reels - the last couple of rolls around the 'core" are very 'springy" - to the point that it can jam in the camera - I usually cut shorter 30-32 frames of these last 2-3 rolls - less problem pulling of the tape on the roll.
Ambient humidity also plays a roll - too dry - it will curl. Vancouver is good this way - we rarely are that dry!
 
There is a very easy and effective solution to your problem. After the film is dry, roll it up with the emulsion side facing outward and leave it like that overnight. The film will be perfectly flat the next day.
 
Gelatin shrinks a bit when it dries after processing. The shrinking surface causes the film to buckle towards the side where it's coated.

Kodak found this problem from the day started making rolled film. With the thinner nitrate bases,the gelatin pulled the base even more strongly that made it really curl. So they made the "NC" (non curling) films. They made this by coating both sides of the base with gelatin. Emulsion on the sensitive side, and clear on the back. With gelatin coats on both sides, the curling tendency was neutralised.

Kodak verichrome, whose base was much thinner than those used in Tmax or Acros, appears to have been double coated too- it dried more slowly, but the strips really dried flat.

AFAIK, Tmax has really thicker bases which minimised curling.

In any case, from a traditional point of view, the slight curling was not really a problem. The curved negatives were originally meant to be placed in clamping negative holders which made them sufficiently flat for printing. Scanning is an afterthought, and the scanners' rollfilm strip holders often have a lot to be desired.
 
ooze (hey I have a friend named ooze) -- i do exactly as you say, quite often. it is actually a more reliable technique than the dictionary on top of the film. but a real solution to my problem would be if kodak and fuji (well if fuji keeps making b&w film, that is) if kodak and fuji made film that dried flat as ilford does.
 
I have found that the biggest factor for this kind of curling is ambient humidity - below 50% and I start to have problems
 
Film flatness

Film flatness

Rollei have got it down. Try Rollei 400S 35mm film. It dries totally flat. Combined with this it has very tight grain and great tonality. Great for scanning. A superb film.
 
Augenblick said:
Rollei have got it down. Try Rollei 400S 35mm film. It dries totally flat. Combined with this it has very tight grain and great tonality. Great for scanning. A superb film.
Click to expand...

Amen to that. All of their films are FLAT FLAT FLAT!!! I particularly like the Retro 80S (stand developed in Rodinal).
 
Haven't tried those Rollei films, but I understand a lot of them have acetate bases (or similar) like my beloved Efke KB25. KB25 dries seriously flat for me. Are these plasticky troublesome light-piping bases very good for drying flat?
 
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