Does emulsion affect/dictate curl?

[bvy]

Does the presence of emulsion affect how much a film strip will curl? In other words, would a strip of minimalist night shots where the film is mostly clear, curl less than a film of beach shots, all else equal? Strange question maybe, but I have my reasons for asking.

 

[Bill Burk]

More often I find the direction and amount of curl to be related to camera (Pentax vs. Olympus). And how recently the film was rewound, or how long it sat on the takeup reel in the camera.

If those are the reasons, the difficulty occurs while loading the reel, before development.

 

[julio1fer]

In my experience, whatever happens to be in the pictures has no influence on film curl. Black or blank frames, it is the same.

 

[jim10219]

With film, you're dealing with plastic that doesn't shrink. Any effect it may have, I assume would be very little, if any, as you dont generally have to worry about curl with sheet film.

 

[koraks]

No emulsion is lost during processing, so the amount of emulsion stays the same regardless of the images being recorded. Even tanning (when using pyro developers) and hardening don't seem to affect curl. Factors that influence curl are the material and thickness of the base, the thickness of the emulsion, the presence or absence of an anti-curl layer on the back of the film (mostly on 120 roll film) and the time the film has been tightly rolled up, to name a few of the more important ones. Drying and storage after processing obviously also have a big influence.

 

[BMbikerider]

Oddly enough I find that film exposed in my later AF slr's which wind the film on with the emulsion inwards, dry almost completely flat in all planes. Whereas film used in either of my Minolta manual focus cameras, where the film is wound on with the emulsion outside of the curl, almost always dry with a longditudinal curl and also a curl across the width of the film as well. I always have to use a negative carrier with glass when printing from these negatives.

With 120 film there is always a very slight concave curl across the film, but never along the length.

I had never actually thought about it until now and always thought it was the conditions the wet film were hung up to dry.

 

[Wallendo]

My experience is that the main factor of curl is the presence or abscence of TX400 . Even then humidity seems to be the main issue. My poorly exposed (usually underexposed) rolls don't curl any more or less than properly exposed rolls developed under the same conditions (and I unfortunately have had a number of underexposed rolls). I sometime expose TX400 at ISO 800 and have noticed no change in the amount of curl.

The main difference between underexposed and overexposed images is the amount of developed silver remaining after fixing. The basic matrix of the emulsion is the same.

 

[bvy]

Let me rephrase my question. I have a scrap piece of undeveloped 4x5 film (T-Max 400, old version, if it matters). It has a little bit of a curl to it, which I want. I'm using it build a film holder of sorts for scanning. The details of that aren't important here. I need the film to be clear though. So the question is, if I fix the film to clear it, will I lose the curl?

 

[darkroommike]

Let's speculate and list a few things that might affect film curl:

• Processing the film may affect the curl in unpredictable ways,
• The curl may be a product of the thickness of the emulsion gelatin layer on one side and the thickness of the annihilation, anti-curl layer on the base side.
• Rehydrating the gelatin and then drying it again may affect the curl in unpredictable ways as can the way it is redried and to what humidity level.
• Even the process of making the base material puts a curl in the film base. Most film base is extruded, shined up by passing it through super polished rollers, and then reeled up onto large rolls. It is then coated, dried, and rolled again before ultimately being cut and packaged.

 

[Rick A]

Let me rephrase my question. I have a scrap piece of undeveloped 4x5 film (T-Max 400, old version, if it matters). It has a little bit of a curl to it, which I want. I'm using it build a film holder of sorts for scanning. The details of that aren't important here. I need the film to be clear though. So the question is, if I fix the film to clear it, will I lose the curl?

Emulsion does have some effect on curl, or more so cupping with roll film.The emulsion does shrink some, and since there is no emulsion on one side of the film base, it does cause a slight amount. If you want zero curl or cupping, soak the sheet of film in household bleach(do it outdoors) and strip the emulsion from the film.

 

[koraks]

Let me rephrase my question. I have a scrap piece of undeveloped 4x5 film (T-Max 400, old version, if it matters). It has a little bit of a curl to it, which I want. I'm using it build a film holder of sorts for scanning. The details of that aren't important here. I need the film to be clear though. So the question is, if I fix the film to clear it, will I lose the curl?

Maybe, maybe not. It's hard to tell. But the odds are you can keep the curl just about the same. The curl is caused by the emulsion shrinking while the base doesn't, hence, the entire sandwich of emulsion+film bends. If you simply (bleach and) fix your sheet/scrap of film and then wash and dry it, it is likely to curl again if it is presently curled.
However, when it comes to curling 4x5 film, and particularly Tmax films, I find that they are just about the flattest pieces of film I've had in my hands. Foma tends to curl a little in 4x5, so you may have better luck there if you actually need a bit of curl to your test film.
Perhaps, if you need some curl, you can try to wash a scrap of film (thoroughly wet the emulsion), then fix it in a slightly bent position and dry it with a hairdryer.

 

[AgX]

The OP is not referring to emulsion as such, but silver content in the processed negative to affect curl.