Re: Gelatin coating on film base?

----- Original Message -----
From: "Monnoyer Philippe" <monnoyer@imec.be>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Monday, March 08, 2004 2:14 AM
Subject: RE: Gelatin coating on film base?

> Sandy,
>
> I think that some films would have such a coating for
anti-halo or mechanical purposes.
>
> Philippe
>
> -----Original Message-----
> From: Sandy King [mailto:sanking@clemson.edu]
> Sent: Sunday, March 07, 2004 04:46
> To: alt-photo-process-l@skyway.usask.ca
> Subject: Gelatin coating on film base?
>
>
> Can anyone tell me if film has a gelatin coating on the
base side or
> is that side just plain polyester?
>
> Sandy King
>
  Nearly all sheet and roll film have a back coating of
gelatin which compensates for the shrinkage of the emulsion
coating to reduce curling of the film. Many films have an
anti-halation dye in this gelatin. The dye is decolorized
during processing but the gelatin coating is not removed.
Some films do not have the coating. For instance, motion
picture release print film doesn't because it is too
vulnerable to scratching.
  Color films also have an anti-curling back coating but
most have an anti-halation layer under the emulsion. I
believe that some Agfa B&W film also has a coating under the
emulsion.
  I don't know when such coatings were first applied but
certainly by about 1930. Kodak introduced Kodak N.C. roll
film film (Non Curling) about 1930.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com