What causes pinholes in negatives?

[robert_gertler]

What causes pinholes in negatives? I am referring to those very tiny spots on the negative that have no density. On the print, these appear as very dark tiny dots. 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 susceptible) or are they due to processing? Is long storage of unexposed film in freezer a cause? Is development to N+2 or N+3 a cause? Lastly, what are the cures to prevent them?

Thanks,

Rob

[psychophoto]

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_chinn1]

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_garrison]

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.