What AGFA had to say about pinholes...

[Michel Hardy-Vallée]

... in 1910:

"Pinholes or minute white specks are very common, and
are caused by small particles of dust settling on the plate or
film while it is being handled in loading the plate holder, mak-
ing the exposure, or developing, the developer thereby being
prevented from properly acting upon the sensitive film. To
avoid pinholes, carefully dust the plates, both when loading
and just before developing, using either a camel's hair brush or
a soft velvet covered pad, both of which must be kept clean and
dry. The camera should also be frequently and carefully
dusted inside. "

From The "AGFA"-Book of Photographic Formulae
http://ia310906.us.archive.org/1/it...0barrrich/agfabookofphotog00barrrich_djvu.txt

 

[Photo Engineer]

Yep. That is why sheet film seems to suffer more from pinholes too.

And, dust after exposure is another reason. A good prewet helps eliminate post exposure dust pinholes and airbells.

PE

 

[Alan9940]

I mentioned pinhole issues in another post, but I thought it might be due to use of acid stop. PE set me straight! That said, I've only ever experienced this issue with roll film; never with sheet film and I've handled quite a bit of that. Come to think of it...what I was seeing might have been airbells...dunno. I doubt seriously, though, if dust was the cause because the "clear spots" were way too precise and uniform in appearance with hard edges.

 

[Photo Engineer]

A true pinhole caused somehow by loss of emulsion or a manufacturing defect will be a crater if examined under magnification. This is very often a coating defect. When hand coating on paper, you can actually see the pinholes form, but with the proper melt viscosity they fill in and cause no problem. Bad viscosity, wrong temperature, or lack of filtration to remove particles and bubbles will cause pinholes during the manufacturing step.

A pinhole in soft film, caused by gas such as carbon dioxide will cause a blister to form as the gelatin stretches around the gas. The blister may burst or may deflate. Either way it forms a rather large defect on the surface of the film or paper. The gelatin has to go somewhere as it stretches and fills with gas.

When dry, gas formed blisters appear as smeared image or as a scale like surface on the print or negative. They are generally larger than those caused by manufacturing defects.

PE

 

[JeffD]

I'd be interested in hearing how people successfully eliminate pre-exposure dust. The camel hair brush idea makes me nervous, as, I would be afraid of introducing dust on the neg which wasn't there to begin with.

I have started cleaning the inside of my bellows more often, as I suspect that dust flakes must be somehow coming from here. I recently blew the inside of my bellows out with an aircompressor, and wiped the inside of the bellows with a very lightly moistened washcloth.

It seems that maybe static might be causing tiny dust specs to be attracted to the film, from the inside of the camera, but I can't confirm this. I have a small anti static "gun" that I used to use cleaning vinyl records, but I haven't tried to utilize this when loading negatives. I might cause more problems that I solve!

 

[lee]

A true pinhole caused somehow by loss of emulsion or a manufacturing defect will be a crater if examined under magnification. This is very often a coating defect. When hand coating on paper, you can actually see the pinholes form, but with the proper melt viscosity they fill in and cause no problem. Bad viscosity, wrong temperature, or lack of filtration to remove particles and bubbles will cause pinholes during the manufacturing step.

A pinhole in soft film, caused by gas such as carbon dioxide will cause a blister to form as the gelatin stretches around the gas. The blister may burst or may deflate. Either way it forms a rather large defect on the surface of the film or paper. The gelatin has to go somewhere as it stretches and fills with gas.

When dry, gas formed blisters appear as smeared image or as a scale like surface on the print or negative. They are generally larger than those caused by manufacturing defects.

PE

when I had pinholes that I could not attribute to dust I switched from acid stop to water and the pinholes NEVER returned. Solved my issues perfectly.

lee\c

 

[Snapshot]

Hmm... I was under the impression that pinholes were the result of not properly fixing the film with acid fixers. I'll now be aware they can be caused by dust. A pre-wet is sounding more and more like a good idea.