[pure-silver] Re: silver in b&w films
----- Original Message ----- From: "Dana H. Myers" <dana.myers@xxxxxxxxx> 
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Saturday, May 31, 2008 12:42 PM
Subject: [pure-silver] Re: silver in b&w films



Janet Cull wrote:

Hello,
At our Thursday night film group, a man came from the close-by camera club which is mostly digital shooters. He came to talk to the newbies about elements of a good pic; composition, lighting, exposure, etc. When he was asked about archivalness (is that a word??) of his prints he said that b&w prints from today's films are not really archival. He said that eventually, in light, b&w film prints will also fade.
He said today's b&w films don't really have silver in them. It seems I've heard that about the t-grain films (is that what you call TMax?) or that maybe the silver is reduced. Is that so across the 
board with the new b&w films?

He said when "pan" was removed from the
names, at that time the silver was either removed or reduced. 

Is this so?  Thanks.


Let's take this one part at a time.  First of all,
conventional B&W film - the stuff you process in B&W
developer - still forms the image from silver like it
always did.  Silver content varies between films, and
T-grain films are reputed to have less total silver
content, but the film is generally as archival as
ever (note that archival qualities for B&W film are
dominated by how the film is processed and stored).

Now, *prints* are potentially a different story.

Conventional B&W papers - the kind you develop in
B&W paper developer - still forms the image from
silver like it always did.  Again, conventional
B&W papers are just as archival as ever (again,
dominated by how the print is processed and stored).

It's also true that many labs don't make prints on
B&W paper; they make monochrome prints on color paper.
Color paper forms the image from dyes, with varying archival 
quality.
The archival qualities of the paper and film are completely 
independent.

As far as I know, dropping the word "Pan" from
film names had nothing to do with removal of
silver or reduced archival qualities of film.

Sounds to me like this "expert" is mistaken.

Dana
I agree with all of the above. Silver is still the basis of all B&W films, including the chromogenic ones although the final image in those is not made of silver. Regular B&W film and paper has not changed in its fundamental properties for 120 years. The abbreviation "pan" meant only that the film was panchromatic, that is, sensitized for the entire visible spectrum, nothing more. Color sensitizing is done mostly be adding certain kinds of dyes to the emulsion during its manufacture. Elementary silver halide emulsion is sensitive to blue and near ultra-violet light and some types (silver iodide) has some natural sensitivity to green. By adding dyes the color sensitizing can be extended into the red or even infra-red. Films which are sensitized to green light are called Orthochromatic and have tone rendition of colored objects which is better than "color blind" or "ordinary" films which are sensitive only to blue light. The dyes for orthochromatic sensitizing were discovered in the late 19th century. Dyes for panchromatic sensitizing were discovered not much later but early pan films had a reputations for having low contrast or being a bit grainy. By the mid 1920s pretty good pan films were available. The motion picture industry tended to stay with ortho films because they were used to them but the changed in production techniques brought about by the introduction of sound forced the industry to adopt pan film and learn to use it. Ortho film was made into the 1960's for various purposes, box cameras and some press work. However its hard to find any now. In any case the color sensitizing has no effect whatever on the longevitity of the image on either film or paper. The main causes of degradation to the image are oxidation and sulfurization. Both are the results of environmental polutants. Of course improperly processed film or paper can be attacked by the residual chemicals it contains but its easy to eliminate this cause. Prevention of damage from airborne polutants can be significantly reduced by toning properly. Other sources of damaging polutants come from storage containers and can be eliminated by proper choice of materials. Another source of damage is degradation of the support. For many years film was coated on cellulose nitrate. This is an inherently unstable material. With time it begins to decompose and some of the products of decomposition also damage the image. This has been a very major problem for the motion picture industry who used nitrate base film from the beginning until 1951 when all production of nitrate was discontinued. However, its replacement, cellulose acetate, can also suffer from chemical instbility and certain types have proven no more long lived than nitrate. In fact there is nitrat film in existence wich is over a century old and still in good enough condition to recover the images from it but some acetate film has destroyed the images it carries in less than fifty years. Other types of acetate seem to age without this problem. Currently some films are made on support similar to Mylar and are considered to be extremely long lived. The life of paper support can be predicted from existing prints on paper which are approaching 150 years old and from other paper documents which are centurys old. I think this guy was confusing color photography with silver-gelatin B&W when he remarked that there was no silver in the image or that it was removed. This is true of color where the image is composed of dyes but not at all of conventional B&W films and papers. Tabular grain (T-Max, Delta, Acros) emulsions are made in a way that encourages the silver halide to form crystals which are in the shape of flat plates rather than in cubes. It has a greater surface area so it can be more sensitive to light and will have greater covering power for a given amount of silver per area. Because tabular grain emulsions can be made very thin they tend to have better resolution and shapness than conventional cubic emulsions. There have been a great many changes in the composition of emulsions and in the way they are made over the last century or more leading to substantial improvement in performance. However none has contributed to any loss of image longevity, rather the opposite is true. 

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