What causes pinholes in negatives?

[Robert Gertler]

What causes pinholes in negatives? I am referring to those very tiny spots on t he negative that have no density. On the print, these appear as very dark tiny d ots. I am currently struggling with this problem with 4x5 Agfapan 100 developed in FX-1, then processed in acetic acid stop bath, Kodafix, and Permawash. Are pinholes due to flaws in manufacture (if so, are some brands more or less susce ptible) or are they due to processing? Is long storage of unexposed film in fre ezer a cause? Is development to N+2 or N+3 a cause? Lastly, what are the cures t o prevent them? Thanks, Rob

[David R Munson]

Pinholes are generally caused by one of two things, from what I gather. First off, dust. Dust on the surface of the film will prevent exposure locally and cause the film under the dust to lack density after processing. Whether or not people think of these things as dust spots or pinholes will vary from person to person, I think. Second, and I may be a little off base on this so if anyone knows better please feel free to correct me, pinholes can be caused by the use of an acid stop bath following an alkali developer. The reaction of the acid and base may cause tiny bubbles of gass to form under the emulsion of the film and at times pop the emulsion off in tiny places, thereby causing pinholes. Certain emulsions, Kodak HIE high speed infrared comes to mind, seem to be more prone to this and most emulsions nowadays rarely exhibit this kind of behavior.

[Jim Chinn]

Eliminate the acetic stop bath and use water. According to Anchell and Troop in The Film Dveloping Cookbook an acetic stop used in combination with a developer containing carbonate such as FX-1 will lead to pinholes and reticulation and may cause clumping of grain. They also recommend slightly shorter development times due to the fact that development will continue for a brief time when water is first introduced. I changed from acetic to water bath about 5 years ago and never noticed any change in negative density.

[Pete Watkins]

If you're going to eliminate an acdic stop bath I would also use an alkali fixer such as TF 3 (mix it yourself) or TF 4 if you're in the states and can buy it. Pete.

[Raven Garrow]

Proccessing. I work in a profesional lab, we use a Pro Jobo machine, and when I print with a neg we proccessed, there sometimes are tiny marks that don't come off. Sometimes, I can remove them with a film cleaning liquid. Now that I think about it, seems it tends to be with the 4x5 film. FYI, the water bath the film goes through as the last proccess, there tends to get a build-up of this residue stuff in the sink where that water is empytied. I think this is the stuff that causes it.