[pure-silver] Re: what causes pinholes in emulsion?

These holes are actual tears in the emulsion rather than dust spots.
I always use distilled water for the developer, but it's possible that the stop or the fix had particles in them that caused some kind of abrasion on the emulsion. If I see it again, I will start filtering my solutions with coffee filters as you suggest. I think my tanks are pretty clean.
Maybe I should use the brita filter when I make up my stop and fix solutions rather than just using tap water. 

--shannon


On Feb 20, 2009, at 4:53 PM, Richard Knoppow wrote:
----- Original Message ----- From: "Shannon Stoney" <shannonstoney@xxxxxxxxxxxxxxx> 
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Friday, February 20, 2009 11:32 AM
Subject: [pure-silver] what causes pinholes in emulsion?
I am printing some film that I shot over a year ago, and there are lots of pinholes in the emulsion. At first I thought it was the brand of film, and one roll did seem worse than the others: the Bergger roll. But the problem is on the FP4+ negatives too. Maybe it was something in my processing that day? I seem to remember that if the temperature difference between the developer and stop is too much, like if the developer is warm and the stop is really cold, it can happen. Is that right? 

--shannon
Pinholes are nearly always a manufacturing problem, check to see if there are actual voids in the emulsion or if there is something else there. An example is dust on the negative during esposure which can leave clear spots which mimic pinholes. Incompletely dissolved chemicals in developer mixed from powder can do the same as can dirt in the developer. The particals are deposited on the surface and prevent full development. Sometimes even rapid agitation will not dislodge them. Air bells, i.e., bubbles formed on the surface of the emulsion during development can also mimic pinholes although air-bells are generally larger and often have a dark ring around the clear spot. The problem of bubbles of gas forming in the stop bath and causing disruptions of the emulsion is extremely rare, for one thing, this outgassing takes place only in developers containing carbonates, few current film developers have them. Developers like D-76 (with Borax) or Xtol (metaborate) do not outgas. Further, modern emulsions are very hard, most B&W emulsions are hardened about the same as color film, that is, to take 100F processing temperatures. In the past, meaning in the 1920s to about the late 1930s, emulsions were much softer and sometimes pinholes would form due to gas bubbles forming. Generally, temperature differences between baths have little effect on modern films for the same reason as stated above. In any case, the results would be softening of the emulsion by hot solutions with attendant swelling and sudden shrinking when placed in the cold solution causing reticulation, i.e., fine wrinkles, in the emulsion. This has a very characteristic look and is not the same as pinholes. I have never heard of pinholes being formed by temperature diffences. Reticulation is sometimes done delibrately as a special effect but is very hard to accomplish with modern film. 
    I have also never heard of pinholes being formed due to film age.
Since you are getting the same effect with more than one brand of film I would be much more suspicious of dirty developer pr dirt in the tank than anything else. First step is to wash the equipment very thoroughly and second step is to filter the processing solutions. Coffee filters work OK for this and are cheap. See if your tap water is dirty. If it is try boiling it and then filtering it through a Brita filter. This will remove particulate matter, drive off dissolved gasses and coagulate and remove any organic matter (bits of tree root) in the water. It will also remove some types of "hardness". A three minute rapid boil followed by allowing the water to stand until cool will do. Decant the clear water and run it through the Brita or similar filter to remove stuff that boiling does not remove. Such treatment is probablly not necessary but some areas have bad water that needs it. At the least filter the water you use for photographic purposes through a coffee filter. 
    Also, vacuum out your camera or cameras.

--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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