Basic Photography Course

You should consult the film data sheets or the

Photo-Lab-Index for the recommended developers for
each particular type of film to be processed.

CHANGES IN DEVELOPER WITH USE

The function of a developer is to change chemically

the sensitized material treated in it. It stands to reason
then that a chemical change also takes place to the
developer itself. Most developers are used more than
once. Therefore, you must know what changes to the
developer can be expected and what can be done to
prevent them or at least compensate for them. The
primary changes that occur to a developer as it is used
are as follows:

Some developer is removed or carried out with

the film and on the film hangers or reels.

The developing agents are used up by reduction

of silver halides to black metallic silver and by aerial
oxidation. When the developing agents are used up by
the reduction of silver halides, the by-products of the
reaction cause the pH of the solution to drop, thus
becoming more acid. When the developer agents are

used up by oxidation, the pH tends to rise.

The preservative is used up, thus the developing

agents oxidize faster.

The bromide within the solution is increased

because the bromide is released from the film emulsion

itself.

The effects of these changes to a developer are as

follows:

The development time required to reach a given

contrast index or gamma is increased. Therefore, when
a developer is used over and over, development time

must be increased as more film is developed.

The effective film speed produced by the

developer decreases because of the increased bromide
(a restrainer) in solution. However, this speed loss may
be partially offset by increasing development time to
maintain image contrast.

Complete exhaustion of a developer occurs when

the developing agents are all used up. The approach of
exhaustion is characterized by a brown color of the
solution. Since a developer in this state can stain
sensitized materials, it should not be used.

In most Navy imaging facilities, it is not economical

to use a developer to the practical exhaustion point and
then discard it. The quality of the image usually suffers

long before the exhaustion point of the developer is
reached. Replenishers are usually used to prevent this
from happening.

Replenishment of a developer involves replacing

those chemicals in the used developer that are exhausted
by a replenisher so that the developer remains
consistent. The aim of replenishment is not to keep the
composition of the developer constant but to keep its

activity constant.

There are two commonly used methods of

replenishment. The first or "topping off" method is used
extensively in tank processing. When topping off is
used, the developer solution is maintained at a constant
level in the tank by adding replenisher, so the volume
added is equal to the amount of developer carried out.
When you are replenishing by this method, it is possible
to maintain consistency in development for only a
certain period of time. After a given volume of
replenisher has been added to the developer, the
developer must be discarded. This procedure is then
repeated with new developer.

The second replenishment method is called the

"bleed" method. The bleed method is used primarily
with machine processing where a circulating developer
system is used. In the bleed method, used developer is
drained off and replenisher (in proportion to the amount
of film processed) is fed in, so the characteristics and
the level of the developer in the machine remain
constant.

FIXING, WASHING, AND DRYING

As soon as a light-sensitive material is developed,

it contains a visible silver image, but the image is not
ready to be exposed to light. Only a portion of the silver
halides in the emulsion were reduced to black metallic
silver by the developer. The silver halides that were not
reduced restrict both the immediate usefulness and the
permanence of the image. These undeveloped silver
halides must be removed. This is the purpose of the
fixing bath. Before treating the sensitized material in the
fixer (as it is called), you must stop or at least slow down
the action of the developer. When the light-sensitive
material is removed from the developer solution, there
is a small amount of developer both in the emulsion and
on the surface that must be removed or neutralized. For
this, you use either a water rinse bath or an acid stop
bath.

10-4

contents

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 -> You should consult the film data sheets or the Photo-Lab-Index for the recommended developers for each particular type of film to be processed. CHANGES IN DEVELOPER WITH USE The function of a developer is to change chemically the sensitized material treated in it. It stands to reason then that a chemical change also takes place to the developer itself. Most developers are used more than once. Therefore, you must know what changes to the developer can be expected and what can be done to prevent them or at least compensate for them. The primary changes that occur to a developer as it is used are as follows: Some developer is removed or carried out with the film and on the film hangers or reels. The developing agents are used up by reduction of silver halides to black metallic silver and by aerial oxidation. When the developing agents are used up by the reduction of silver halides, the by-products of the reaction cause the pH of the solution to drop, thus becoming more acid. When the developer agents are used up by oxidation, the pH tends to rise. The preservative is used up, thus the developing agents oxidize faster. The bromide within the solution is increased because the bromide is released from the film emulsion itself. The effects of these changes to a developer are as follows: The development time required to reach a given contrast index or gamma is increased. Therefore, when a developer is used over and over, development time must be increased as more film is developed. The effective film speed produced by the developer decreases because of the increased bromide (a restrainer) in solution. However, this speed loss may be partially offset by increasing development time to maintain image contrast. Complete exhaustion of a developer occurs when the developing agents are all used up. The approach of exhaustion is characterized by a brown color of the solution. Since a developer in this state can stain sensitized materials, it should not be used. In most Navy imaging facilities, it is not economical to use a developer to the practical exhaustion point and then discard it. The quality of the image usually suffers long before the exhaustion point of the developer is reached. Replenishers are usually used to prevent this from happening. Replenishment of a developer involves replacing those chemicals in the used developer that are exhausted by a replenisher so that the developer remains consistent. The aim of replenishment is not to keep the composition of the developer constant but to keep its activity constant. There are two commonly used methods of replenishment. The first or "topping off" method is used extensively in tank processing. When topping off is used, the developer solution is maintained at a constant level in the tank by adding replenisher, so the volume added is equal to the amount of developer carried out. When you are replenishing by this method, it is possible to maintain consistency in development for only a certain period of time. After a given volume of replenisher has been added to the developer, the developer must be discarded. This procedure is then repeated with new developer. The second replenishment method is called the "bleed" method. The bleed method is used primarily with machine processing where a circulating developer system is used. In the bleed method, used developer is drained off and replenisher (in proportion to the amount of film processed) is fed in, so the characteristics and the level of the developer in the machine remain constant. FIXING, WASHING, AND DRYING As soon as a light-sensitive material is developed, it contains a visible silver image, but the image is not ready to be exposed to light. Only a portion of the silver halides in the emulsion were reduced to black metallic silver by the developer. The silver halides that were not reduced restrict both the immediate usefulness and the permanence of the image. These undeveloped silver halides must be removed. This is the purpose of the fixing bath. Before treating the sensitized material in the fixer (as it is called), you must stop or at least slow down the action of the developer. When the light-sensitive material is removed from the developer solution, there is a small amount of developer both in the emulsion and on the surface that must be removed or neutralized. For this, you use either a water rinse bath or an acid stop bath. 10-4 contents Basic Photography Course <- previous page next page ->	As an Amazon Associate I earn from qualifying purchases.
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