Replenisher may be added to a developer when the quantity has fallen below the working level of the
tank. Enough may be added to return the developer to its proper working level.
Replenisher may be added to a developer after a certain amount of film has been developed. After 800
square inches of film have been developed in a 4-gallon solution, 8 ounces of replenisher may be added
to the developer, even if this involves discarding a small amount of the original developer.
A good check on the strength of the developer solution is to shoot a dozen pictures of a subject.
Develop one when the developer is first mixed. As the developer is used, develop another one.
Compare the last negative with the first negative developed; when the contrast and density of the
negative fall below normal, discard the developer solution.
Water of crystallization
Care must be taken in the proper use of chemicals as to the amount of water they contain. The less
water a dry chemical contains, the stronger it is. There are three common forms of chemicals used in
photography. They are classified according to their water content.
a. Desiccated--Contains no water; dry.
b. Monohydrated--Contains one molecule of water per hydrate.
c. Decahydrated--Contains 10 molecules of water per hydrate.
One question which usually comes to mind about water of crystallization is, "Why not make all
chemicals desiccated or dry?" This brings into the discussion the stability of that chemical to remain in
the form in which it was made. Some chemicals absorb moisture form the air and others give off
moisture into the air. The stability of a chemical is expressed in the following manner:
a. A stable chemical is one which will not absorb from, or give off moisture into, the air. It
remains in its original form.
b. An efflorescent chemical is one which will become drier by giving off moisture to the air.