[pure-silver] Re: how did these scratches happen?


On Mar 4, 2008, at 9:41 AM, Nicholas O. Lindan wrote:

"Shannon Stoney" <shannonstoney@xxxxxxxxxxxxxxx>
[pure-silver] how did these scratches happen?
http://www.flickr.com/photos/shannonstoney/

White scratches happen because either the emulsion was distressed before developing or the back of the film was scratched. All
the marks are parallel and the squiggles track so the chances
are the scratches were made by being scraped over an edge.

Aha!!! Sometimes when I roll the film onto the reels, I trail it over the side of a table in the darkroom. I bet that's it.



The black bits, though, are confusing - they look like tiny gouges made in the emulsion by, say, the emulsion being pressed
against sand particles.

The black bits are gouges made in the emulsion. Can that happen when the emulsion is dry, or only when it's wet?



Questions:

1) What brand & type of film?

HP5+


2) Is this the only frame with the marks?

Yes.


3) Have you had the marks before?

Not recently.


4) On what side of the negative do you see the scratches?

Emulsion side.


5) What do the little gouges look like under a magnifying
  glass?

Holes.


6) The marks are on the negatives, right?  Not just the print?

Right.


7) Is this a scan of the negative or the print?

The negative.



The marks are not due to processing and are not
photoflow/drying marks.

Right, that was a separate question.


Marks from film dried without/too little photoflow and/or
hard water look like white puddles, rivers, shorelines and tear-drops. Bacterial growth in photoflow produces smudgy stringy marks.

That's what it looks like.


If you are getting streaks with photoflow the reasons are most
likely: using tap water (water softeners or Brita filters will
just make things worse); using old _diluted_ photoflow; not letting
the film sit in the photoflow long enough to let it enter the emulsion; wiping the film down with something dirty.

I used distilled water to dilute the photo flo. I let it sit 30 seconds as it says on the bottle. I didn't wipe it.
It was fresh.


Photoflow stock solution does not go off, however working strength
photoflow will support microbe growth - it can be seen as a white
slimy cloud.  I dilute PF 1:20 with 91% isopropyl alcohol - pour
~3/4 oz (25 ml) into a pint (500 ml) bottle of drugstore alcohol and
mark the bottle with a Sharpie. I then dilute this 1:10 with distilled water just before use as the final rinse. I let the film soak in the rinse for about a minute with light agitation/swirling. Most people let the film drain naturally - I dip two fingers into the photoflow and use them to lightly squeegee the film.

==
Nicholas O. Lindan
Cleveland Engineering Design, LLC
www.darkroomautomation.com Cleveland, Ohio 44121

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