Gelatin (waterproofing)

Is it possible to prevent a dried gelatin layer from taking up
moisture from the atmosphere? Is it possible to prevent
water in contact with the layer from swelling the gelatin?
(In essence, waterproofing the gelatin)

-Phillip

Ryuji Suzuki wrote:

> From: Richard Knoppow <dickburk@ix.netcom.com>
> Subject: Re: Dreaded fungus
> Date: Wed, 17 Dec 2003 22:00:06 -0800
>
> > Most hardeners of the
> > sort found in fixers harden the emulsion only when it is
> > wet. I think formaldehyde may actually harden it when dry.
>
> Note that any hardner hardens the gelatin and gelatin is hardened
> whether it's wet or dried. The difference is that the antiswelling
> effect of hardening is seen when the emulsion is wet, not when dry.
>
> Gelatin always retains some amount of water, depending on the RH of
> the air. Hardening does not affect much in gelatin's absorption of
> water at high RH. (OTOH, at very low RH, emulsion may shrink and
> become excessively curly and brittle, whether it is hardened or not.)
>
> Formaldehyde is not a very desirable form of hardening agent in
> emulsion making for several reasons, but it is a quite effective
> hardening agent. Yet, its hardening has little influence on the
> absorption of water vapor from air at high RH.
>
> Dry strength is more strongly influenced by the gelatin
> structure. When the emulsion is dried slowly at chilling low
> temperature, the gelatin is in a gel structure, while when dried fast
> at high temperature, the gelatin is in sol structure. The gel
> structure is the desired form in terms of dry mechanical
> properties. The gel structure also responds to hardening agents better
> than the sol structure. Although modern coating facility design is a
> tight trade secret, patents in this area generally describe very fast
> coating of very thick emulsion on film or paper, and the coated
> material is immediately chill set and dried in dry, cold environment.
>
> --
> Ryuji Suzuki
> "Reality has always had too many heads." (Bob Dylan, Cold Irons Bound, 1997)
Received on Sun Dec 21 07:52:04 2003