Basic Photography Course

MIXING, TESTING, AND STORING

EQUIPMENT

The type of material, used for photographic

chemical mixing, solution testing, storing, as well as
film-handling equipment, must be considered before
mixing chemicals. Materials commonly used in the
construction of this equipment are Type 316 stainless
steel, polyethylene, and glass. Related equipment,
such as solution transfer lines, mixer shafts, impellers,
and machine parts, are also made of these same
materials.

Some metals are not suitable for use with photo

solutions. Serious chemical fog and developer changes
can be caused by tin, copper, brass, and bronze.
Aluminum, lead, nickel, zinc, galvanized iron, and
Monel, when used with developers and fixers, can be
harmful to films and papers. When these metals are

used, silver thiosulfate from the used fixer may stick to
them. Even when the utensils are washed after being in
the fixer, enough silver thiosulfate can be transferred to
the developer in the next processing or mixing run to
cause stain, fog, or changes to image tone.

Wooden paddles and other absorbent materials

must not be used with photographic solutions. Once
they have been used, it is almost impossible to wash
them clean of absorbed chemicals.

MIXING CONTAINERS

Chemicals should always be mixed in cylindrical

containers made of suitable materials, The size of the

mixing container should be suitable for the amount of
solution to be prepared. A small batch of solution
should not be mixed in a large vessel that uses
mechanical agitation because large amounts of air
may be introduced, and splashing may occur. So, the
mixing container, and for that matter, scales and
graduates, should be sized to the quantities and
volumes of solutions required.

GRADUATES

Graduates are used to measure liquids. Graduates

are made in various sizes, calibrations, and of various
materials. The units of measure of graduates are
calibrated in the U.S. liquid measurement system of
ounces, quarts, and gallons, and in the metric liquid

measurement system of cubic centimeters, milliliters,
and liters.

Glass is most commonly used for making graduates

because it is NOT affected by most chemicals. Glass
is also transparent and reasonably durable. Graduates
are also made from plastic and stainless steel. When
using graduates made of plastic, do not try to measure
strong acids, such as sulfuric acid, which could cause
severe damage. You must also be sure that the material
the graduate is made of does not react with any of your
photographic chemicals.

For accuracy in measuring liquids, graduates

should be proportional in size to the quantity of
solution being measured; for example, an 8-ounce
graduate should be used instead of a 32-ounce
graduate to measure 2 or 3 ounces.

When measuring a liquid in a glass graduate, hold

it at eye level and pour the solution into it until the
surface of the liquid reaches the correct mark. You will
notice a curved surface on the top of the solution. This
curved surface is called the "meniscus." The correct
amount is indicated by the lower of two visible lines
of the meniscus (fig. 9-1). These two lines can be seen
easily through the side of a glass graduate when it is
held correctly. With an opaque graduate, such as
stainless steel, the two lines can be seen by looking
down into the graduate from an angle. Stop pouring
the solution when the "lower line" of the liquid
reaches the calibration mark. Major divisions are
indicated by numbers on the graduate. Subdivisions
are shown by calibration lines only. You must
determine the value of the individual subdivisions; for

example, the marked or numbered lines may indicate
ounces and read in series of 10. When there is only
one calibration line between each graduation of 10,

then the value of the calibration line is 5.

THERMOMETERS

All chemical action takes place faster at high

temperatures than at low temperatures. In the
photographic process, when you mix or use a solution,
you must know its temperature.

Thermometers are used to measure the temperature

of the solution and may be made of glass or metal. The

average glass thermometer consists of a bulb, containing
either mercury or colored alcohol, attached to a capillary
tube. This tube may be calibrated or it may be secured
to a graduated scale. When you are reading a

9-2

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Basic Photography Course

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DOFMaster for Windows On-line Depth of Field Calculator DOFMaster for Mobile Devices On-line Depth of Field Table Hyperfocal Distance Chart Articles FAQ Recommended Books Support Contact Links Home As an Amazon Associate I earn from qualifying purchases.	contents <- previous page next page -> MIXING, TESTING, AND STORING EQUIPMENT The type of material, used for photographic chemical mixing, solution testing, storing, as well as film-handling equipment, must be considered before mixing chemicals. Materials commonly used in the construction of this equipment are Type 316 stainless steel, polyethylene, and glass. Related equipment, such as solution transfer lines, mixer shafts, impellers, and machine parts, are also made of these same materials. Some metals are not suitable for use with photo solutions. Serious chemical fog and developer changes can be caused by tin, copper, brass, and bronze. Aluminum, lead, nickel, zinc, galvanized iron, and Monel, when used with developers and fixers, can be harmful to films and papers. When these metals are used, silver thiosulfate from the used fixer may stick to them. Even when the utensils are washed after being in the fixer, enough silver thiosulfate can be transferred to the developer in the next processing or mixing run to cause stain, fog, or changes to image tone. Wooden paddles and other absorbent materials must not be used with photographic solutions. Once they have been used, it is almost impossible to wash them clean of absorbed chemicals. MIXING CONTAINERS Chemicals should always be mixed in cylindrical containers made of suitable materials, The size of the mixing container should be suitable for the amount of solution to be prepared. A small batch of solution should not be mixed in a large vessel that uses mechanical agitation because large amounts of air may be introduced, and splashing may occur. So, the mixing container, and for that matter, scales and graduates, should be sized to the quantities and volumes of solutions required. GRADUATES Graduates are used to measure liquids. Graduates are made in various sizes, calibrations, and of various materials. The units of measure of graduates are calibrated in the U.S. liquid measurement system of ounces, quarts, and gallons, and in the metric liquid measurement system of cubic centimeters, milliliters, and liters. Glass is most commonly used for making graduates because it is NOT affected by most chemicals. Glass is also transparent and reasonably durable. Graduates are also made from plastic and stainless steel. When using graduates made of plastic, do not try to measure strong acids, such as sulfuric acid, which could cause severe damage. You must also be sure that the material the graduate is made of does not react with any of your photographic chemicals. For accuracy in measuring liquids, graduates should be proportional in size to the quantity of solution being measured; for example, an 8-ounce graduate should be used instead of a 32-ounce graduate to measure 2 or 3 ounces. When measuring a liquid in a glass graduate, hold it at eye level and pour the solution into it until the surface of the liquid reaches the correct mark. You will notice a curved surface on the top of the solution. This curved surface is called the "meniscus." The correct amount is indicated by the lower of two visible lines of the meniscus (fig. 9-1). These two lines can be seen easily through the side of a glass graduate when it is held correctly. With an opaque graduate, such as stainless steel, the two lines can be seen by looking down into the graduate from an angle. Stop pouring the solution when the "lower line" of the liquid reaches the calibration mark. Major divisions are indicated by numbers on the graduate. Subdivisions are shown by calibration lines only. You must determine the value of the individual subdivisions; for example, the marked or numbered lines may indicate ounces and read in series of 10. When there is only one calibration line between each graduation of 10, then the value of the calibration line is 5. THERMOMETERS All chemical action takes place faster at high temperatures than at low temperatures. In the photographic process, when you mix or use a solution, you must know its temperature. Thermometers are used to measure the temperature of the solution and may be made of glass or metal. The average glass thermometer consists of a bulb, containing either mercury or colored alcohol, attached to a capillary tube. This tube may be calibrated or it may be secured to a graduated scale. When you are reading a 9-2 contents Basic Photography Course <- previous page next page ->	As an Amazon Associate I earn from qualifying purchases.
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