curved film

[wbesz]

Can anyone advice me how to prevent 35mm film from drying curved?

(The curve is across the width, like a concave)

I notice that commercially processed film comes back dead flat!

My film is dried in a large diameter PVC sewerage pipe which has

a dust cap roof over the top, and takes about 4 hours to dry at

room temerature. Am I doing something wrong?

Thanks for any sound advice.

William

[arden_howell]

I use a weighted film clip on the lower end of my film strip and air dry. The freshly dried film still has a slight curl towards the emulsion, but nothing that will hinder getting a flat negative in my carrier. I store cut negative strips in sleeves in a 4 inch binder and after a few days they are dead flat. What you are experiencing seems quite normal to me depending on the severity of the curl. Incidentally, unless you are heating the air in your drying tube, four hours seems a little on the short side. Although seemingly dry to the touch, negatives at this stage can still be easily damaged as I learned the hard way.

[canon man]

You should also bee careful not to move the tube from one place to another that might be different temperature. The change in temperature can cuase the emulsion to crack due to the difference of drying rates while drying. We saw eveidence of this last term in school when a classmate kept having thecracks. It ws pointed out by another classmate that had attendd the Brooks Institute. Don't ask me why, it just does. Just something else to be careful of. Cheers.

[john_rice1]

Daniel, what you are talking about is called Reticulation, and it

actually doesn't happen very easily. You usually have to go to

great lengths to get it to happen.

 

William, what you are talking about is pretty common. If you heat

dry your film at just the right temp, it will come out flat on it's own.

A lower temp will curl toward the emulsion and a higher temp

will curl toward the base, so air drying will generally curl toward

the emulsion. You can reduce the curling by using a

non-hardening fixer like Ilford Multigrade fixer, or not adding the

hardener to two part fixers. Many fixers are one part with the

hardener in it, so you can't exclude it. Using a non-hardening

fixer will make the emulsion more delicate until the film is dry,

but makes no difference once it is dry.

 

One possible, small problem I see is that the tube you use is

capped on top. Unless there are some holes, the moisture can't

escape and the film won't completely dry until after it is taken out

of the tube. Otherwise, I usually just put the dried negs in pages

and then put some weight on them overnight. Then they come

out flat.

[wbesz]

Thanks for the suggestions. I feel John's answer is the one I

was looking for. The cap on top of my drying tube has a 10mm gap around it for the moisture to escape but keep dust out, and the room is around 20 degrees C. I will now make a heater with low voltage flashlight bulbs and a temperature controller to see what temperature I need for drying the film flat (I will place the heat source on the bottom).

William

[john_rice1]

I bet you'll need more heat than that. I think you'll need it to be

somewhere around 100 degrees. I think, the proper temp

changes with humidity. I don't heat dry my film, so I'm really not

sure how that all works. I am sure about the drying temp

affecting the curling of the film, though. Back in College we had

heat dryers and our film came out flat.

[jerry_hyman2]

I have found that certain films tend to curl more than others. For example Kodak's TechPan really curls a lot where TMAX100 and Tri-X don't seem to hardly curl at all. I think some of the Ilford films tend to curl more than Kodaks.

 

I also agree with John in that leaving out the hardner makes a big difference.

 

-Jerry

[rbradbury]

Another trick is, after washing, roll the film onto the reel emulsion side out, then dip in photo flo and allow to dry. This counteracts the tendency to curl toward the emulsion.

[chris_waller]

No, don't worry. When I dry 35mm film in my dryer it curls, but as it cools it flattens and after filing in neg sleeves it flattens completely.

[travis1]

Just dry with weights attached to the end, and then when dried, forced them into film strip holders and keep them for 24hrs. I have been doing that. No curl.

[wbesz]

A question to Chris Waller. Do you know the temperature of your dryer? And perhaps, how long does it take for the film to dry (in the dryer)? The answer may help to explain the physics of why film can dry with little or no curl. Thanks.

[mendel_leisk]

>I notice that commercially processed film comes back dead flat!

 

Me too! How do THEY do it? Any pros?

[scott_walton2]

Years ago I made a dryer out of a plastic hanging garmet bag. The ones you

pick up at Kmart/Walmart with a clear front and a zipper the full length. All I did

was run string up top (using plastic cloths pins to hold the film top and

bottom), poke a hole in the top for my wife's old hair dryer (use on low) and a

few slits in the bottom. When you turn the hair dryer on the whole bag

balloons up and I have never had any problems... dried film in about 15

minutes, dust free and when done I just fold the bag up flat and store it! The

full length bag would hold 10 rolls of 35mm with no problems.