Black and White Photography

Changing bag. When a darkroom is not available, you can load film onto your
processing reels and tank in a collapsible, lighttight sack called a changing bag.
It has a zipper opening and two holes that let you put your hands inside while
keeping light out. You use the zipper opening to put the film, reel, and tank in,
and then place your hands through the holes to load the film, without having
to turn off the room lights.
You will need several different chemicals for processing film. All are packaged
in either powder or liquid form, depending on type and brand. Although they
are often more expensive, liquids are more convenient, easier to use, and generally
safer to handle than powders. Powders must be mixed with water to make
a stock solution, the form in which chemicals are generally stored. Chemicals
that come packaged as liquids are, in effect, premixed stock solutions.
Some stock solutions are used straight (undiluted) but more often you must
dilute the stock solution with water for use. The usable form of the chemical
(whether diluted or undiluted) is called a working solution. Stock solutions generally
stay fresh longer than working solutions, although many working solutions
can stay fresh for months as long as they are stored in containers without
much excess air inside.

Following are the required film-processing chemicals, in order of use. Note

that print processing requires most of the same chemicals, with slight variations.

For example, there are different developers for film and paper.

Film developer. The developer is the most important processing chemical because

it forms the image, turning exposed film into negatives. It does so by

reacting with the film emulsion’s light-sensitive crystals and converting them to

black, metallic silver. The greater the film exposure, the denser the concentration

of developed silver. Areas of the film that received a lot of exposure (light

subject areas) turn darkest; areas that received less exposure (dark subject

areas) appear proportionally lighter or clearer on the negative.

There are many different brands of film developer, in powder and liquid

form, each with its own characteristics. Some developers produce finer or

coarser grain than others, while others produce greater or less contrast. Whatever

their properties, all film developers do develop film effectively.

Depending on the brand, you must prepare and use stock solutions of developer

in various ways. With some, you don’t dilute the stock solution at all; the

stock solution, in effect, also is the working solution. With others, you dilute

the stock solution with water, to make the working solution, for example, 1:1

(1 part developer to 1 part water). Still others require a heavy dilution, as much

as 1:25 (1 part developer to 25 parts water) or even more. You can use different

dilutions for most brands of developer, but the dilution you choose has an

important effect on the developing time. Refer to instructions on the developer

package or label for proper handling and dilution recommendations. Such

information also will be on the film and developer manufacturer’s Web site.

Many film developers are one-use, meant to be discarded after processing.

Some types can be chemically replenished and used for months or even longer.