The Chemistry Behind Black and White Photography

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.

Dear F,

 

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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.

 

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Regards

Wolfgang

It depends on how much detail you want. Just about any basic book on

photography will tell you about the exposure/development process.

 

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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.

 

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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.

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).

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.

Another excellent resource is.... Photographic Chemistry and

Processing. Edited by Sidney F. Ray. Focal Press. 1994