Someone's Finger Print On My Negative...And It Ain't Mine!

[Alan Edward Klein]

I ALWAYS wear nitrile gloves when loading/unloading sheet film holders. This is definitely a first for me. HP5 8x10. I wonder who the dirty culprit was?

View attachment 419637

Looks like you had some schmutz on your nitrile-covered thumb that dried up with lines.

 

[Andrew O'Neill]

Looks like you had some schmutz on your nitrile-covered thumb that dried up with lines.

Nope. Fresh out of the box.

 

[pbromaghin]

 

[pbromaghin]

Check out the textured fingertips on this nitrile glove.

 

[Andrew O'Neill]

@pbromaghin I'm not sure what I should see. Mine aren't textured.

 

[mshchem]

View attachment 419737

Yep, doesn't look like a fingerprint.

 

[mshchem]

I'm going to be looking for fingerprints on all my Kentmere 200.

 

[pbromaghin]

@pbromaghin I'm not sure what I should see. Mine aren't textured.

You should see a textured nitrile glove. This is the first that you have indicated that yours are not.

 

[cowanw]

I think it is the outside lateral edge of a thumb, which is very nuch a linear pattern and would be easy to imagine grasping sheet between thumb and index finger; likely ET's

 

[Melvin J Bramley]

Have Interpol or the CIA run the image through their computers to find the culprit.
Chances are there is a Kodak 'mole' working at Ilford!

I still think it's Andrews fingerprint.

 

[250swb]

That's not very consistent with how a film coating operation works.

8x10 sheet film is more or less 'hand made', along with the niche sizes they can make to special order. It's not like switching on the production line to make 5,000 rolls of 35mm HP5. At some point when enough has been made the machine needs cleaning down ready for the next type of emulsion or film format. I've been on the factory tour and quality control is very high, but no quality control system is perfect.

 

[koraks]

8x10 sheet film is more or less 'hand made', along with the niche sizes they can make to special order. It's not like switching on the production line to make 5,000 rolls of 35mm HP5.

You're mixing a couple of things up here. You said earlier it looked like a blob of emulsion that found its way onto the film in the coating procedure, through some kind of roller offset mechanism. But that doesn't make any sense. The coating and finishing processes are separate parts of the process. The 'hand made' part refers mostly to how the sheet film is packaged. At this stage, no wet emulsion is anywhere near the product. The coating process itself, where there's actually wet emulsion, doesn't involve rollers that have blobs of emulsion on them and that would offset a fingerprint pattern onto the film. The emulsion is basically poured onto the film through a series of narrow slots; no roller touches the emulsion-side of the film as the emulsion is wet.

The confectioning stage only follows once the film is thoroughly dry; after coating, the film is dried in a drying gallery and by the end of this it's either rolled up in master rolls, or slit and rolled in pancakes. No wet emulsion is anywhere near the film at this point. So the first time anything physically touches the coated emulsion side of the film is in a physically different location from where the wet emulsion is (which doesn't come into contact with open air in any space before it's being coated). After slitting into pancakes, sheets can be cut from the appropriate rolls (i.e. those made with the sheet film base); this cutting operation is very definitely not a manual operation, but the bagging & boxing can very well be because it's relatively expensive to automate this. Again, no wet emulsion is in the actual space where this would happen, so there's really no chance of wet emulsion finding its way onto the film through this route.

The fingerprint to me looks like sensitized emulsion that developed out during processing, with the fingerprint forming the route of sensitization. My guess would be sulfur compounds on the skin acting as a fogging agent. Sulfur is a common element and is known to be a powerful fogging agent, so this would be a likely candidate.