Want to avoid backing paper problems: How 'safe' to use out of date 120 film that's been refrigerated?

[FredK]

Backing paper problems can affect films in different ways. They all form from the same findamental flaw of the backing paper where the surface of the paper, which despite rolling and calendeering, is still rough at the microscopic level, is not surface treated enough to eliminate that roughness. Surface treatment involves the coating of a protective overcoat on top of the paper. The paper's roughness embosses the emulsion surface overcoat layer with the same type of roughness, or variation in height. For all films, that height differential will "allow" developing agents into the silver grains faster and more through the process where the their was embossing of the overcoat layer. The increased developer leads to over development in those areas, and a pre-soak will minimize this risk as it will swell the gelatins and allow any embossing to minimize prior to the developer reacting with the exposed silver grains.

For high speed films that feature flat shapped grains (like T-grains), the extreme winding pressures in 120 film spools coupled with the roughness and time can lead to the silver grains becoming pressurized where embossing has occurred. Pressurization of those grains can lead to additional density (sensitization) or loss of density (desensitization) and this is dependent on the film design so it could be different reaction for different films employing those type of silver grains.

Lastly, if the emulsion overcoat gelatin and its surface has a greater tackiness, and the spools have been exposed to moisture before (out of the wrapper) or even after exposure with time, and the protective overcoat layer of the backing paper is not thick enough, ink transfer can occur where the backing paper information can relocate onto the emulsion which will prevent development underneath.

So, a manufacturer's backing paper problem can affect all of their films in very different manners. Some, but not all, can be mitigated by a pre-soak, and for any old films I would recommend that be employed going forward.

 

[Prest_400]

So, a manufacturer's backing paper problem can affect all of their films in very different manners. Some, but not all, can be mitigated by a pre-soak, and for any old films I would recommend that be employed going forward.

Very interesting and the overcoat for the backing paper is what Kodak went for.

Sometimes I think, and guess that due to material properties or such, that if it is so costly with the paper why not replace it with an opaque plastic eg. Kodak makes ESTAR and probably could very well adapt and manufacture an opaque rough "backing film"; or well, they just coat or have it supplied with the overcoat now.