2. Types of chemicals. There are many types of chemicals, too numerous to
name, but we can categorize them into two basic groups. They are:
black and white chemicals
a. Black and white chemicals can be further divided into the following
(1) Film chemicals
(2) Paper chemicals
b. The color chemicals can also be broken down into the following
(1) Negative chemicals
(2) Printing chemicals
(3) Positive/reversal chemicals
3. Black and white chemicals. When we refer to chemicals, we mean the
chemicals that come in premixed containers. They come either in powder or
liquid form ready to be mixed with water to make a working stock solution.
a. A stock solution is mixed with water to get a base solution for
temporary storage in bottles. When needed, this solution is further diluted
with water, and after use, it is discarded. Examples of this are paper
developers and some film developers, such as DK50.
b. A working solution is one that is used as is. That is, once the
chemical is mixed with water, it is ready for use. Examples of this are
most film developers, stop bath, and fixer.
c. To give a general idea of the makeup of different chemicals, we have
a simple chart for mixing DK50, stop bath, and fixer form base chemicals.
d. In Figure 11 is a list of some of the black and white chemicals
commonly used in the military. This list contains the names or numbers of a
chemical, it's most notable characteristics, and storage life. You should
perform a processing test on chemicals which have been stored for extended
periods, even though the chart indicates they may still be good.