Must transparent-base films be curly?

[Argenticien]

(In all of this, I'm discussing black & white negative emulsions in 120 size.)

A question for the materials scientists, chemical engineers, and similar out there: Is there an inextricable relationship between transparentness* of film base and curliness? I've just processed my first two rolls of Rollei Ortho 25, which has a very clear (near-transparent) base, and it is horribly, unmanageably curly. Pressing the cut strips of one roll with heavy books overnight did little to nothing. Ditto with reverse-rolling the other roll overnight. This is the same problem I had with Efke 25 (peace be upon it), and I saw similar reported in a recent thread about PolyPan. Is there some force of nature that prevents these slow, clear films being flatter? Pan F Plus 50 is the least curly slow film I've seen, but it is slightly less clear, although of course nothing like the deep grey of for example Delta Pro 400.

--Dave

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* I'm aware that "transparentness" probably isn't a word. I'm deliberately avoiding the more proper "transparency" to avoid any confusion with E-6 film.

 

[Bob Michaels]

I am not familiar with the films you mentioned but I know back long ago that Kodak Tech Pan and 2475 high speed recording film were on a special clear Estar base that curled like crazy. Tech Pan supposedly used that base because it was "dimensionally stable" to accommodate the high resolution requirement. I imagine the 2475 high speed recording film was to utilize the clear base thus increasing the effective iso.

I never found a way to deal with the strong tendency to curl of that clear Estar base but maybe someone else did.

 

[Moto-Uno]

My experience with the Efke 25 and 50 film were similar to yours (were they made in a propeller factory?). I believe I'd read elsewere that the extremely thin emulsion layer had something to do with it. But that may be out in left field too. Peter

 

[ruby.monkey]

Ortho 25 really calls for a betterscanning holder with ANR glass, but Retro 80S and 400S both have a completely transparent base and dry flat.

 

[Argenticien]

Thanks all, for replies so far. I foresaw the advice to use BetterScanning holders with glass. 🙂 Yes, I have $h!te flimsy OEM Epson holders. I've deferred buying BS ones only because I've got a creaky Epson 4490 and the BS holders for it would not fit a V700, to which I hope to upgrade soon. After upgrading, then I'll get the BS holders (V700 size). But honestly, some of these films are so curly that they would require at least three hands to hold them flat and position the ANR glass and close the film holders. As it is, even with cut strips of the Rollei 25 in a PrintFile negative preserver page, the whole page rolls up into a tight tube and I need three hands to simultaneously unroll it and get a heavy book atop it without kinking the negs. Can all this bollocks really be what the film manufacturers intended?

--Dave

 

[charjohncarter]

Efke 820 IR (now dead), Efke R25, Bluefire Police are/were my most difficult film with curls.

 

[Fotohuis]

All Polyester films are more curly. But Efke films had a single non curling layer where the Retro (S) Synthetic series from Agfa Gevaert have a double non curling layer. The same had R3 from Rollei.
The new Ortho films are produced by OrWo Filmotec on Polyester base. The type of wetting agent and the drying speed of the film are mainly responsable for the best result in less curl.

 

[Argenticien]

All Polyester films are more curly. But Efke films had a single non curling layer where the Retro (S) Synthetic series from Agfa Gevaert have a double non curling layer. The same had R3 from Rollei.
The new Ortho films are produced by OrWo Filmotec on Polyester base. The type of wetting agent and the drying speed of the film are mainly responsable for the best result in less curl.

Robert, thanks for those details. That's interesting. Maybe I am part of the problem then! I'm using Ilford's Ilfotol wetting agent. Rather keeping a dilute working solution on hand, I just create it in real time by adding 5 to 7 drops of the concentrate to plain water in my developing tank (which is about 570 ml) and of course mix well. I then unroll and hang the films to air-dry naturally, so presumably somewhat slowly. Often I don't watch the drying at all 🙂 -- as I will frequently process film late at night, then go to sleep and let the film dry until the next morning. But in cases when I have come back to check on films, I think they took about 2 hrs to dry.

These Rollei Ortho 25 rolls were already very curly when hung up to dry; it's not that they were flat to start with and then curled only during drying.

--Dave

 

[Fotohuis]

The old ortho 25 films from Rollei were produced by Efke. And indeed they were curling like hell.
The new version I did not tested yet myself.
A slow dry up within 2-3 hours is perfect. To fast means more curl.

 

[Moto-Uno]

I've mentioned this previously and enjoy saying it again. I have and use an Epson V600
scanner, the film holders bring no joy to scanning negs. I'm cheap ( Scotch heritage, & detest their national drink , that should raise a few eyebrows). I place a thin piece of glass cut by a local window business ( $6) over the negatives,they lie perfectly flat,scan easily and are easily lined up. Ignore the remarks about having the negs a specific distance from the scanners bottom glass. I have some of the propeller negs in it now and they scan fine.
TRY IT, before spending film money on holders. Peter

 

[citizen99]

Not exactly [120 + B&W + negative] as per OP discussion, but FWIW :-
o Recently used 127 Rollei Crossbird curled strongly enough to lift the 4mm (5/32 inch) thick ANR glass on top of it 😡
o Whereas, using Agfacolor 50 35mm and 120 transparency films in the '60s and '70s, I found no unusually significant curling 🙂

 

[Denverdad]

As I was commenting in this thread, the drying method may be a big factor here. I use a Senrac Rapid Rollfilm Dryer and honestly haven't had any significant curl issues with any film, including Efke 25. My sense is that drying on the reel constrains the film to stay flat in the short axis, and if it dries flat it stays flat.

 

[Sejanus.Aelianus]

There's a useful PDF from Kodak that explains how films are coated. I believe that the anti-halation layer reduces the curl by balancing out the main coating. As a consequence, if I have this right, any clear film base will tend to curl because the coating shrinks on drying, the base does not shrink and there's nothing to counter the difference.