adequate ventilation, a complete air change every 3
minutes, and an exhaust fan to the outside atmosphere
in the area where chemicals are mixed.
by chemicals. Glass is the best material. Stainless steel
is a highly suitable material, provided it is of the proper
composition. Hard rubber and glazed earthenware may
also be used satisfactorily. Acid and alkali-resistant
plastic containers are acceptable.
as work is finished with an item of equipment, it should
chemicals are spilled, clean them up as soon as possible.
of chemical you put into a solution is the amount
packaged photo-processing chemicals. Packaged
chemicals come in convenient sizes for most needs.
They offer standardized quality, economy, and
manufactured under tightly controlled conditions. These
packaged chemicals are available in either liquid or
powder form. Processing solutions can be mixed easier,
usually contain more than one ingredient. During
shipping and handling, these ingredients may separate
with the heavier elements settling to the bottom of the
package. When only part of the package is mixed, some
of the ingredients that have separated or settled may not
it is being stirred. When preparing a developer, be
careful while you are stirring so air is not beaten into the
solution. When water is poured on dry chemicals, they
will cake and form hard lumps that are difficult to
another chemical to a solution before the previous part
has been completely dissolved Sometimes there is a
residue that will not dissolve. The residue may be sand
in the water supply, impurities in the chemicals, or other
matter that found its way into the water; however, when
the solution is allowed to stand for awhile, these
particles usually settle and the clear liquid can be poured
off. To remove sludge or dust particles that may not
settle, pour the solution through a funnel containing
three or four layers of cheesecloth or absorbent cotton.
properties. However, the rate of chemical reaction
increases with an increase in temperature, and all
chemicals dissolve more readily in warm water than in
cool water; consequently, many formulas and
instructions recommend that water as hot as 125°F be
used to prepare the solution that must then be cooled to
try to mix solutions at the minimum temperature
faster at higher temperatures because of increased
chemical activity at these temperatures.
cloudy or milky for a short time after it is mixed. This
appearance may be caused by air taken into the solution
by the dry chemicals. Air taken into a solution is
distributed through the solution as tiny bubbles that
cannot escape while the solution is being stirred. When
the presence of bubbles has caused the discoloration, the
solution will clear up when it is allowed to stand for a
while. The bubbles rise to the surface of the solution and
escape into the air.
to pour water into an acid. Some acids generate heat
Basic Photography Course