Film-Tech Forum ARCHIVE: Film Chemistry Question

This is topic Film Chemistry Question in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Ed Inman (Member # 2583) on 06-28-2006, 03:51 PM:

I suppose this question is unusual but since several people here are associated with Kodak, various film labs, etc., I thought someone might have an answer.

Is there a chemical that will dissolve a silver soundtrack without affecting the color emulsion?

For instance, would a traditional B&W bleach formula such as Kodak R-9 (dichromate and sulfuric acid) in conjunction with a socium sulphite clearing bath successfully remove the silver without damaging the color picture? Or perhaps some other formula I'm not familiar with?

I have an old trailer that was printed on the release stock backwards, i.e. the soundtrack is printed onto the color emulsion and the silver track appears as a dark bar down the right side of the picture.

It won't play at all with an exciter lamp but it plays ok with a red LED Jaxlight. So if there is a way to dissolve the silver without harming the color image I would then have a good trailer.

thanks for any suggestions,

Ed

Posted by Phillip Grace (Member # 2262) on 06-29-2006, 03:14 AM:

Hi Ed.
Bleach then Fix should work. You might try your nearest motion picture lab, and see if they would run it through their Positive processing machine. Caution is advised though. You will need to have some idea of the age of the film, as the higher temperatures in the current process may strip the emulsion completely. If you read the specifications of the current Kodak ECP process (ECP 2B?) you will get a good idea of which steps in the process to use.

Posted by John Pytlak (Member # 331) on 06-29-2006, 09:01 AM:

I agree, running the film through the ECP-2D process again without soundtrack application should remove most of the silver (through the action of the bleach and fixer), although a slight stain may remain. Any print film made for the ECP-2 process is fine, but earlier films were not forehardened, and will NOT survive the hotter ECP-2 process.