I would like to learn the chemistry behind black and white photography, specifically how the element silver is involved in the process. Any information would be greatly appreciated.

-- F. King (kdj2412@aol.com), March 29, 2000

Answers

Dear F,

During the exposure a latent image wil be build. This latent image is invisible. To make it visible you need a process which is a kind a intensity. This process is called development. During the development the silverhalide crystals which are exposed will be reduced to metallic silver. Two criterias are important that photographic emulsions can be developed: The exposed crystals must developed faster than the unexposed so that there is a differentiation between exposed/unexposed. An electrochemical precondition for a development is that there is a potential difference. That means the redox potential of the developing system has to be more negative than the silver ion Ag+/metalic silver Ag. On the other hand the potential difference should not be to negative. Otherwise there would not be a differentiation between exposed and unexposed crystals. There is much more to explain but it would be to much for the moment, I guess. If you would like to have more information please contact me. I try to answer your queries as good as I can.

Regards Wolfgang

-- Wolfgang (wolfgangrh@gmx.net), March 30, 2000.

It depends on how much detail you want. Just about any basic book on photography will tell you about the exposure/development process.

If you want a lot more information there is "The Darkroom Cookbook" and "The Film Developing Cookbook." These go into the chemistry to the extent of telling what the various chemicals used actually do.

For the most detail is the book by Stoebel, something like Photographic Processes and something. I forget right now. But this is a college textbook level book on the entire photographic process.

-- Terry Carraway (TCarraway@compuserve.com), March 30, 2000.

You may find a partial answer to your question in my article on Mixing Developers at http://unblinkingeye.com. I start with the fundamentals of photographic chemistry. Much of the magic of the photographic process is inherent in the peculiar properties of silver halide crystals and the imperfections (i.e., "sensitivity centers") inherent in them. The imperfections are essentially silver ions (atoms of silver lacking an electron) that are positively charged. When photons strike the silver halide molecules, the energy level of various electrons are raised and they flow to the positively charged silver ions and form atoms of pure silver, which are known as latent image specks. These latent image specks act as "seeds" which allow the developing agent to begin the process of reducing the halides to pure silver. There is an excellent reference that I base much of my information on: George T. Eaton's "Photographic Chemistry" (Morgan & Morgan, 1957).

-- (edbuffaloe@unblinkingeye.com), March 30, 2000.

If you really want to go nuts with the physical chemistry and electrochemistry of photography, go to your local university library and see if they have a copy of The Theory of the Photographic Process. It is out of print, but it I've seen it in libraries. It is not a reference for the faint of heart, and a college level chemistry background will be really helpful in understanding a lot of what is in there, but even a shallow perusal of the work is very informative. While you are there, look for a copy of the Encyclopedia of Photography. There is a lot of good information in there too.

-- Fritz M. Brown (brownf@idhw.state.id.us), March 30, 2000.

Another excellent resource is.... Photographic Chemistry and Processing. Edited by Sidney F. Ray. Focal Press. 1994

-- Chris Hawkins (peace@clover.net), April 03, 2000.