Basic Photography Course

WATER RINSE BATH

To slow down the action of development, you must

immerse the film in a water rinse bath. A plain water
rinse bath is commonly used between development and
fixation to slow down the development by removing all
the developer that is clinging to the film (or paper)
surface. A rinse bath does not completely stop
development but retards it. A rinse bath has little affect
on the developer that is actually in the swollen emulsion.

Rinsing is accomplished by quickly immersing the

film in plain, clean water. A water rinse bath should be
changed often to ensure it does not become loaded with
developer. It is better to use running water.

The rinse bath, then, serves two purposes: first, it

slows down development and second, it reduces the
work that has to be done by the acid in the fixer. Rinsing,
therefore, protects or prolongs the useful life of the fixer.

Following rinsing in plain water, the material (that

is still light sensitive) must be treated in an acid fixing
bath to stop the development.

ACID STOP BATH

Although a plain water rinse bath is commonly used

between development and fixation, a better procedure is
to use an acid stop bath. The function of a stop bath is
not only to remove the developer that is clinging to the
surface of the material but to also neutralize the
developer in the swollen emulsion to stop development
completely.

The acid stop bath stops the action of the developer

because developing agents cannot work in an acid

solution. An acid stop bath also helps protect or prolong
the life of the fixer by neutralizing developer carry-over.

An acid stop bath should meet the following

requirements:

lThe pH must be low enough to neutralize the

action of the developer carried over.

The acidity should be limited so the small amount

carried over into the fixing bath does not increase the
free-acid content of the fixing bath and cause
sulfurization.

It must not contain enough acid to produce blister

formations in an emulsion.

You should use only a weak acid stop bath between

development and fixation. Strong acid and the acid in
the fixing bath have a tendency to form carbon dioxide

gas bubbles in the emulsion. When the film is taken from
the developer and placed directly into a strong acid or
fixing bath, these bubbles may break and cause small,
round holes in the emulsion. These bubbles are
sometimes mistaken for pinholes like those caused by
dust particles settling on the emulsion before camera
exposure.

When you are using an acid stop bath, remember

that some of the stop bath is carried into the fixer when
materials pass through it. Therefore, you cannot use a
strong acid (such as sulfuric acid) because it can cause
precipitation of sulphur in the fixer. Acetic acid is the
type of acid used for stop baths. In its pure form as
glacial acetic acid (99.5 percent), it freezes at a
temperature of about 61°F. Its freezing tendency gives
it the name "glacial." For use as a stop bath, 99.5 percent
glacial acetic acid is diluted with water to make a 28
percent working solution. Approximately 1/2 ounce of

28 percent acetic (not glacial) acid is added to 32 ounces
of water. The process of determining the concentration

of a liquid is discussed in chapter 8.

FIXING

When a light-sensitive material is removed from the

developing solution, the emulsion contains a large
amount of silver salts (halides) that has not been affected
(developed) by the developing agents. This silver salt is
still sensitive to light, and if it remains in the emulsion,
light ultimately darkens and discolors the salt which
obscures the image. Obviously, when this action occurs,
the negative (or print) is useless.

The fixing bath is used to prevent this discoloration

and to make the developed image permanent. It
accomplishes this by removing the undeveloped silver
halides by making them water soluble. Therefore, to
make an image permanent, you must "fix" the
light-sensitive material by removing all of the
unaffected silver salt from the emulsion.

The fixing bath contains five basic ingredients: the

fixing agent, preservative, neutralizer or acidifier,
hardening agent, and an antisludge agent.

Fixing Agent

All fixing baths must contain a silver halide (salt)

solvent. This solvent is known as a fixer or fixing agent.

The two most commonly used in photography are
sodium and ammonium thiosulfate, commonly termed
hypo (taken from their other chemical name
hyposulfite). Ammonium thiosulfate is used in rapid

fixers that are stronger and require less fixing time.

10-5

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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 -> WATER RINSE BATH To slow down the action of development, you must immerse the film in a water rinse bath. A plain water rinse bath is commonly used between development and fixation to slow down the development by removing all the developer that is clinging to the film (or paper) surface. A rinse bath does not completely stop development but retards it. A rinse bath has little affect on the developer that is actually in the swollen emulsion. Rinsing is accomplished by quickly immersing the film in plain, clean water. A water rinse bath should be changed often to ensure it does not become loaded with developer. It is better to use running water. The rinse bath, then, serves two purposes: first, it slows down development and second, it reduces the work that has to be done by the acid in the fixer. Rinsing, therefore, protects or prolongs the useful life of the fixer. Following rinsing in plain water, the material (that is still light sensitive) must be treated in an acid fixing bath to stop the development. ACID STOP BATH Although a plain water rinse bath is commonly used between development and fixation, a better procedure is to use an acid stop bath. The function of a stop bath is not only to remove the developer that is clinging to the surface of the material but to also neutralize the developer in the swollen emulsion to stop development completely. The acid stop bath stops the action of the developer because developing agents cannot work in an acid solution. An acid stop bath also helps protect or prolong the life of the fixer by neutralizing developer carry-over. An acid stop bath should meet the following requirements: lThe pH must be low enough to neutralize the action of the developer carried over. The acidity should be limited so the small amount carried over into the fixing bath does not increase the free-acid content of the fixing bath and cause sulfurization. It must not contain enough acid to produce blister formations in an emulsion. You should use only a weak acid stop bath between development and fixation. Strong acid and the acid in the fixing bath have a tendency to form carbon dioxide gas bubbles in the emulsion. When the film is taken from the developer and placed directly into a strong acid or fixing bath, these bubbles may break and cause small, round holes in the emulsion. These bubbles are sometimes mistaken for pinholes like those caused by dust particles settling on the emulsion before camera exposure. When you are using an acid stop bath, remember that some of the stop bath is carried into the fixer when materials pass through it. Therefore, you cannot use a strong acid (such as sulfuric acid) because it can cause precipitation of sulphur in the fixer. Acetic acid is the type of acid used for stop baths. In its pure form as glacial acetic acid (99.5 percent), it freezes at a temperature of about 61°F. Its freezing tendency gives it the name "glacial." For use as a stop bath, 99.5 percent glacial acetic acid is diluted with water to make a 28 percent working solution. Approximately 1/2 ounce of 28 percent acetic (not glacial) acid is added to 32 ounces of water. The process of determining the concentration of a liquid is discussed in chapter 8. FIXING When a light-sensitive material is removed from the developing solution, the emulsion contains a large amount of silver salts (halides) that has not been affected (developed) by the developing agents. This silver salt is still sensitive to light, and if it remains in the emulsion, light ultimately darkens and discolors the salt which obscures the image. Obviously, when this action occurs, the negative (or print) is useless. The fixing bath is used to prevent this discoloration and to make the developed image permanent. It accomplishes this by removing the undeveloped silver halides by making them water soluble. Therefore, to make an image permanent, you must "fix" the light-sensitive material by removing all of the unaffected silver salt from the emulsion. The fixing bath contains five basic ingredients: the fixing agent, preservative, neutralizer or acidifier, hardening agent, and an antisludge agent. Fixing Agent All fixing baths must contain a silver halide (salt) solvent. This solvent is known as a fixer or fixing agent. The two most commonly used in photography are sodium and ammonium thiosulfate, commonly termed hypo (taken from their other chemical name hyposulfite). Ammonium thiosulfate is used in rapid fixers that are stronger and require less fixing time. 10-5 contents Basic Photography Course <- previous page next page ->	As an Amazon Associate I earn from qualifying purchases.
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