Using a power mixer: When this type of mixer is used, care should be taken that the shaft is NOT
placed in the center of the solution being mixed. When the shaft is in the center, a whirlpool effect is
formed and air is admitted rapidly into the solution, causing it to oxidize. Also, a little pile of chemicals
will form directly beneath the blades and these chemicals will dissolve very slowly.
Weighing chemicals:
Chemicals should be weighed or measured to the exact amount called for in the formula. Deviations of
as little as a few grains may change the working characteristics of the solution.
To insure that there will be no contamination of one chemical with another, graduates should be washed
thoroughly after measuring a chemical. The pans on scales should be covered with a separate sheet of
paper for each chemical. Plain paper, used for writing, and typing paper contain a small amount of
sulfur. This may contaminate and ruin some chemicals; therefore, the paper used to cover the pans on
scales should be the black paper which separates each sheet of film in a box. This black paper has no
sulfur content. A new sheet of paper should be used for each chemical weighed.
Dissolving the chemicals:
Chemicals should be completely dissolved in the order given in the formula.
One chemical should be completely dissolved before the next is placed in the solution.
When mixing large quantities of developer containing Metol, the Metol sometimes begins to oxidize
before the preservative is dissolved. To prevent this oxidization, 5% of the preservative may be dissolved
in solution before the Metol; then, the Metol; then the remainder of the preservative, and the rest of the
chemicals in the order given.
Water:
Water which contains a large amount of iron or other impurities should not be used for photographic
purposes. These metals tend to cause decomposition of some of the chemicals in the solution. Distilled
water is the best to use since it is free from all foreign matter. Often, developer troubles can be traced
to impurities in the water.
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