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The main caution in all color darkroom
work revolves around temperature control. Both color film and print
processing demand tight temperature control in some instances to ± 1/4°
F. Several methods exist to control temperatures to this level of
precision. Darkroom devices similar to Color Processor use heating
elements in a water bath to maintain solution temperatures. They
consist of an emersion-type heating element and precision thermostat.
Water temperatures are maintained at proper levels by the unit's heater
cycling on and off as the water temperature cools. The next most
important item in the darkroom is a laboratory-grade thermometer.
Obviously it must be accurate to within 1/4° F to be of any use in
color work. You should be aware that nasty things happen when
temperatures are not maintained to stated tolerances. Wild and
unpredictable color shifts are likely, along with loss of film speed
and major contrast changes.
If economy is important to you, construct a temperature control box of
your own. What you will need is a large plastic tub about 13 x 18
inches and around 6 to 8 inches deep. Purchase a good quality
thermometer if you don't have one already. In addition, locate six to
eight one-pint capped plastic bottles. The critical unit in this
construction is an aquarium heater. Buy the best one you can afford.
To set the unit up for use, fill the tub and bottles with water until
the bottles are submerged to at least two-thirds of their length. Turn
on the heater and gradually bring the temperature up to the desired
solution working temperature. Monitor temperatures of the chemistry in
the bottles and not the water in the tub. When the desired temperature
is arrived at, mark the dial of the heater with the temperature.
Setting the dial at this point in the future will get very close with
only minor adjustments needed to arrive at the precise temperature
again. The procedure described here is slightly more trouble than a
commercially built unit but it does work and it saves money.
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