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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to replenishing photographic silver halide developer
solutions. More particularly, this invention relates to replenishing the
developer used in automatic processors for lithographic film.
2. Description of the Prior Art
Developer solutions used in automatic photographic film processors are
subject to change in composition due to accumulation of development
products, e.g., oxidized developer and halide ion, and to developer aging.
Such changes are particularly critical in processing lithographic film
where the hydroquinone type developer is characterized by high sensitivity
to bromide and sulfite ion concentration and where developer stability is
characterized by high sensitivity to pH, to aerial oxidation, and to
anaerobic degradation. The nature of lithographic development, developers
and replenishers has been characterized in prior art studies such as J. A.
C. Yule, J. Franklin Inst., 239, 221 (1945); L. F. A. Mason, "Photographic
Processing Chemistry", The Focal Press, New York, (1966) pg. 163; D. A.
Pullen & M. C. Lloyd, Printing Technology, 14, 69 (1970); L. T. Connolly,
TAGA Proceedings, 1970 page 151; R. L. Childers, Photogr. Sci. Eng., 15,
480 (1971); and H. Zwicky, Chimia, 26, 667 (1972). In a commercial
lithographic developer hydroquinone is the sole developing agent. To
obtain the lith effect with consistent results, the developer must have a
low, but constant, sulfite ion concentration along with a constant high pH
and bromide ion concentration. The sulfite ion concentration is maintained
by a sulfite buffer, e.g., sodium formaldehyde bisulfite; during use,
however, concentrations of hydroquinone and bromide ion and pH are changed
by the development process. Due to the low sulfite concentration and to
the presence of buffer components, lith developer at high pH (i.e.,
substantially above 8) undergoes a time-dependent loss of activity due to
aerial oxidation and anaerobic degradation. Thus to obtain reproducible
processing, a replenisher solution is normally added to the developer to
compensate for changed activity due to prior use or aging. Replenisher,
however, contains substantially the same components as developer itself,
and consequently is unstable. This poses the problem of attempting to
compensate for the deteriorating activity of the developer with a
replenisher solution whose activity is also deteriorating. In addition to
maintaining developer activity, the concentration of bromide ion in the
developer, which modulates development, should be maintained constant. In
some automatic processors, means are provided for replenishing the
developer periodically by measuring or sensing the activity level of the
developer bath and then adding the appropriate amount of replenisher. OLS
No. 2,119,069 discloses an automatic developer replenishing system which
monitors bromide ion and developing agent concentration and adds, as
required, either replenisher with high bromide concentration or
replenisher with no or low bromide concentration. Schumacher, OLS No.
2,004,893 discloses a replenishment system containing two separate
replenishers in which one replenisher is supplied to the developer on the
basis of the quantity and developer requirements of the film being
developed, and in which a second replenisher is supplied to the developer
on the basis of processor running time. Automatic replenishing systems,
such as that of OLS No. 2,119,069, are normally expensive and use premixed
replenishers, which, like the developer, are unstable. Consequently,
replenisher activity is never the same from one moment to the next, and
the replenisher is frequently discarded if not used within a relatively
short period of time.
SUMMARY OF THE INVENTION
There has been discovered, according to the invention, a process of
replenishing a developer solution whereby the problems of the prior art
are avoided by a procedure in which replenisher solution is made up as
each quantity thereof is added to the developer to compensate for
developer activity lost due to development of a piece or quantity of film.
Since the replenisher is prepared and added as each quantity of film is
developed, the activity thereby restored to the developer bath will be
precisely known and not diminished by the time-dependent degradation of
replenisher. This process is for use with hydroquinone type developers,
which are subject to degradation at high pH but which may be made up from
stable solution concentrates. Accordingly, in the process of developing
exposed photographic film in a bath of developer solution, the improvement
comprises repetitively replenishing said developer solution with a
quantity of replenisher solution which is prepared from at least two
stable solution concentrates and added to said bath of developer solution
as each quantity of film is developed, said quantity of replenisher
solution being predetermined from the concentration of each solution
concentrate and the quantity and developer requirements of said film. The
developer requirements of photographic film depend primarily on the
percent exposure and halide content of the film. The solution concentrates
together contain the necessary constituents to replenish the bath of
developer solution; however, each individual solution concentrate contains
only those constituents which will substantially not interact. Thus, for a
lithographic developer, solution concentrate "A" contains hydroquinone and
a sulfite buffer at a pH below about 8, solution concentrate "B" contains
a base, e.g., free hydroxyl ion, and may contain bromide ion.
As previously stated, a developer solution should have not only a constant
level of active hydroquinone developing agent but also a carefully
controlled sulfite and bromide ion level. To facilitate replenishment to
the proper balance of developer constituents, therefore, there may be
employed a third solution concentrate "C" containing bromide or additional
sulfite buffer or additional hydroquinone. Additional adjuvants normally
used in lithographic developers may be present in each concentrate or in
additional solution concentrates. In the practice of this invention large
reservoirs of stable solution concentrates can be used, thereby
eliminating the inconvenience and expense of discarding and replacing
unused premixed replenisher each day. Similarly, disposal problems of the
waste, unused, premixed replenisher is eliminated.
Furthermore, the invention enables replenishment to be carried out
economically and with precision. Since each quantity of replenisher is
prepared and added as each quantity of film is developed, its composition
at the time of addition to the developer has not been affected by aging
and is therefore precisely known. This permits addition of a given amount
of replenisher solution for film of given quantity and developer
requirements without the need for expensive and unreliable sensing means.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In a preferred embodiment of the invention, lithographic developer in an
automatic photographic film processor is replenished either just prior to,
during or just after development of each sheet of exposed photographic
film by metering perdetermined proportions of three stable, solution
concentrates, one of which is a solution of a hydroquinone developer at a
pH below 8, and mixing the solutions with a metered amount of deionized
water to form just enough replenisher to maintain a desired developer
activity during the development of the individual sheet. The replenisher
can be mixed and immediately introduced into the developer, or
alternatively, the solutions and water can be metered directly into the
developer. When a single long web of exposed photographic film is
processed, developer activity can be maintained by repetitively mixing and
adding replenisher in a predetermined time sequence during development.
Two of the three solution concentrates can be stable stock solutions
normally used to prepare premixed replenisher for automatic photographic
film processors. The third solution concentrate can be primarily aqueous
potassium bromide solution or it can be one of the two stock solutions
with added potassium bromide. A fourth solution concentrate may contain
additional sulfite buffer, hydroquinone, or other specific adjuvants.
The process of the invention is particularly useful in replenishing
lithographic developers containing a hydroquinone developing agent, i.e.,
hydroquinone or a derivative thereof which is subject to degradation under
development conditions but which can be made up from stable solution
concentrates. Representative lithographic developers are described in
Valiaveedan, U.S. Pat. Nos. 3,622,330; Nottorf, 3,325,286; Lowe et al.,
3,158,483; Nottorf, 3,142,568; and Henn et al., 3,030,209. Lithographic
developers frequently contain the following constituents: hydroquinone as
the sole developing agent, 5-75 g; auxiliary solvents, 20-100 g; caustic
alkali, 3 or more g; hardeners or hardener adducts, 5-80 g; preservatives
or antioxidants, 1-40 g; restrainers, 1 or more g; buffering agents,
20-100 g; Sequestering agents, 0.5-4 g; and water to make 1 liter.
Replenisher for such lithographic developers generally contain the same
constituents, however, concentrations of some or all constituents may be
different. Constituent concentration in replenisher depends on
replenishment rate. Solution concentrates useful in the process of the
invention will contain a stable mixture of some of the constituents of the
replenisher however the constituent concentration generally will be higher
and would be limited only by solubility in the solution concentrate.
Concentration used will be further restricted by the predetermined
replenishment rate. At least two solution concentrates must be used to
replenish the developer with the required amount of constituents, and
frequently the replenisher constituents are divided into three or more
solution concentrates. However, in the preferred embodiment three solution
concentrates are used. One solution concentrate, part A, usually contains
hydroquinone and a water miscible organic solvent in an aqueous solution
with a pH below about 8 and preferably below 7. At a pH above 8,
hydroquinone rapidly oxidizes in air. Part A frequently contains sulfite
buffer such as sodium formaldehyde bisulfite as well as other non basic
constituents which are soluble in the organo-aqueous solvent, e.g.,
sequestering agents, surfactants, preservatives, antifoggants and
antioxidants. Auxiliary organic solvents useful in part A are alcohols,
glycols like ethylene glycol, diethylene glycol and triethylene glycol and
glycol ethers like 2-ethoxyethanol or 2-methyoxyethanol. The second
solution concentrate, Part B, is a strongly basic aqueous solution with a
pH generally above 9 and frequently contains sulfite buffer; ionic
restrainers, e.g., potassium bromide; buffering agents, e.g., borate and
carbonate; free sulfite, e.g., sodium sulfite; and surfactants. Part B
contains no hydroquinone, since such solutions are unstable at high pH.
Basic agents generally used to keep pH above about 9 include, alkali metal
hydroxides, ammonium hydroxides, amines, and basic salts, e.g., sodium
carbonate, and bicarbonate. The third solution concentrate, Part C, can be
a concentrated solution of an individual constituent, e.g., potassium
bromide or sodium sulfite, or it can be a concentrated solution of two or
more individual constituents, or it can be either Part A or Part B wherein
one or more of the constituents' concentrations are increased, e.g., Part
B with added potassium bromide. In further aspects of the invention it is
apparent that additional solution concentrates, Part D, etc., with
components similar to those of Part C can be used. The amount of each
solution concentrate used can be expressed in milliliters per square inch
of developed silver.
The amount of each solution concentration to be mixed is predetermined from
the size of the film sheet to be developed, the extend to which the film
was exposed, the type of film used, and the time interval since the
developer was last used or replenished. The amount of concentrate used is
proportional to the size of film sheets to be developed and the percent
exposed area. In the particular case where a reversal film is to be
processed, concentrate used is proportional to the percent unexposed area.
When a film having silver halide with high bromide content is to be
processed, little or no bromide is required in the concentrate, e.g., in,
Part B. But, when the silver halide is high in chloride and low in
bromide, a commensurate upward adjustment in bromide is required from the
concentrate, e.g., either in Part B or Part C, to maintain the developer
at a consistent activity. When consecutive sheets of film having the same
halide content are to be processed only two suitable solution concentrates
are required, Part A and Part B, to replenish the developer before or
during development of each sheet. But when film sheets having different
halide content are intermixed in consecutive processing at least three
solutions concentrates are required, Part A, Part B, and Part C, where
Part C contains more bromide than Part B. The processing of a film web may
be considered equivalent to processing consecutive sheets of film having
the same halide content, the same size (e.g., having the same length and a
width equivalent to the film web width) and the same average exposure. In
this instance, the commensurate amount of concentrate is metered, mixed
and added to the developer at time intervals predetermined from the
equivalent film sheets and the rate at which the film passes through the
processor. During prolonged periods when film is not being processed,
solution concentrates, Part A, Part B and/or Part C, can be metered, mixed
and added to the developer at predetermined time intervals to maintain the
activity of the developer. The time intervals are predetermined in this
instance from known aerial oxidation and anaerobic degradation (e.g.,
hydroquinone reaction with formaldehyde) effects at the developer
temperature or from processed control film strips.
In order to maintain the developer bath at constant activity, it is
therefore desired to add replenisher solution or concentrates therefor at
fixed intervals based on the amount of film processed and age of the
developer. It is preferred that the developer bath be replenished as each
quantity of film from about 1 to 20 square inches of film per liter of
developer solution in said bath, is developed, to compensate for
consumption of developer due to processing and at least as often as once
every 16 hours, and more preferably every 15 minutes to 2 hours, during
periods of use, including standby for use, to compensate for aerial
oxidation and anaerobic degradation of developer. This can be done by
adding replenisher solution, or replenisher concentrates, during regular
time periods in amounts needed to maintain developer activity during a
regular time period when no film is processed, minus the amounts added
during the same time period to compensate for film processed. Thus, at the
end of a regular time period when no film is processed, the maximum
amounts of supplementary solution concentrates will be added to the
developer; at the end of a regular time period when a small amount of film
is processed, the amount of supplementary solution concentrates will be
the maximum amounts required, reduced by the amounts of solution
concentrates added to compensate for the processed film; and at the end of
a regular time period when a large amount of film is processed and the
amounts of solution concentrates required to compensate for the film
processed exceeds the amount of supplementary solution concentrates needed
when no film is processed, then no supplementary solution concentrates are
added. At least two solution concentrates are needed to form the
supplementary combination. In a particularly preferred embodiment using
this procedure, the first solution concentrate Part A is substantially the
same as Part A described above, having pH below 8 and a raised level of
developing agent. The second solution concentrate Part C is substantially
the same as Part B described above except that concentrations of all
components except bisulfite ion will be such that, upon dilution,
component concentrations will be the same as the developer. Bisulfite ion
concentration in Part C is increased to compensate for the expected
time-dependent developer degradation.
Any means known to one with ordinary skill in the art may be used to meter
and mix prepared solution concentrates and add the resultant replenisher
to the developer of the automatic processor. However, for the process of
this invention to be particularly useful the metering, mixing and adding
means should be automatically controlled from a predetermined selection of
parameters. A suitable control apparatus for carrying out the process of
this invention is disclosed in Crowell et al., U.S. Pat. No. 3,822,723.
In practicing this invention the developer requirements of the film to be
developed are determined by methods well known in the art. In one
instance, it is possible to determine the developer requirements of a
particular film type by analysis of the film to determine the amount of
silver halide per unit area and type of halide present. Since one mole of
developing agent, hydroquinone, is needed to develop one mole of silver
halide, the amount of developer used can be determined from an accurate
estimate of the percentage of the area of the film that has been exposed
(percent exposure) if the constitution of the developer is known or can be
analyzed. With the high contrast lithographic films normally used with
hydroquinone as the sole developer, exposed areas develop completely,
simplifying this calculation. The predetermined amount of Part A solution
concentrate contains enough hydroquinone to replace that used in the
developer during development. The predetermined amounts of Part B solution
concentrate and water are sufficient to maintain the pH and constituent
concentrations of the developer. In another instance, where detailed
knowledge of the film type, developer constitution and replenisher
constitution are not known, it is possible to determine the amounts of
replenisher concentrates needed from manufacturers specifications,
directions and the provided developer requirements of the film.
Conventionally, replenisher is supplied by the manufacturer as two stable
solution concentrates, Part A and Part B, along with directions for
preparing premixed replenisher therefrom, and directions for adding the
premixed replenisher to the developer. Thus X amount of Part A, Y amount
of Part B and Z amount of water are mixed to prepare working strength
replenisher and Q amount of the replenisher is added for a given area of
exposed film to be developed. Since the operator of the processor
typically is also the cameraman, the amount of exposed film is estimated
from the size of the film and the nature of the material photographed.
When the manufacturers information for replenishing a particular film type
is inadequate, the processor operator typically determines the amount of
replenisher needed empirically by developing a series of pre-exposed
control film strips and adjusting the replenishment rate "Q" accordingly.
In the practice of this invention, the operator, instead of premixing a
working strength replenisher, would add the proper proportion of Part A,
Part B, and water directly to the processor, i.e., (QX/X+Y+Z) of Part A;
(QY/X+Y+Z) of Part B; and (QZ/X+Y+Z) of water. In addition to the
hydroquinone which must be added replenishing, if the film is a silver
bromo chloride film, the proper level of bromide ion is added in the
replenisher to compensate for the difference between the bromide ion
generated during development and the bromide ion lost in the developer
solution flowing out through the developer tank overflow when replenisher
is added. If the film is a silver bromide film, the film itself adds
greater quantities of bromide upon development so that lower amounts of
additional bromide are needed in the replenisher solution. An additional
replenisher solution concentrate, as previously described, may be
conveniently employed to provide the proper bromide ion concentration.
This invention will be further illustrated by, but is not intended to be
limited to, the following examples wherein commercially available films
were processed in standard developers using commercially available film
processors.
EXAMPLE I
Developer solution was prepared having the composition of Example XI (the
eleventh formulation in the table of developer compositions), of
Valiaveedan, U.S. Pat. No. 3,622,330. The developer solution ( 64 liters)
was put in the developer tank of a LogEtronics Model LD/24 automatic
processor (a product of LogEtronics, Springfield, Virginia).
The following replenisher solution concentrates were prepared.
______________________________________
Part A
Hydroquinone 190 g
Sodium formaldehyde bisulfite
20 g
Ethylene glycol 600 g
Water to make 1 liter
Part B
Sodium hydroxide 40 g
Sodium sulfite 15 g
Sodium formaldehyde bisulfite
320 g
Potassium bromide 5 g
Trisodium ethylenediaminetetra-
acetate trihydrate 8 g
Sodium metaborate (octahydrate)
50 g
Sodium bicarbonate 35 g
Potassium carbonate (anhydrous)
130 g
Water to make 1 liter
______________________________________
A lithographic film containing 30 mole percent AgBr and 70 mole percent
AgCl similar to that in Example I in Nottorf, U.S. Pat. No. 3,325,286 was
cut into sheets 20 .times. 24 inches (480 sq. in.). Ten sheets were
exposed the same way. Half of each sheet was covered with an opaque mask
and an intensity scale step tablet (1.times. 7 in.) along with a magenta
screen was placed on the uncovered half. Each masked sheet was then
exposed for 20 seconds to a white light tungsten source. The exposed
sheets were fed into the processor consecutively, the feed rate of the
processor being 33 inches per minute. Just as each sheet was introduced
metering pumps were activated to meter 40 ml of Part A, 40 ml of Part B
and 160 ml of water into a mixing volume from which the mixed replenisher
was pumped into the processor developer tank within 20 seconds of
activation of the metering pumps. The amount of Part A, Part B, and water
were determined as hereinbefore described. Thus one milliliter replenisher
per square inch of exposed film area (which is transformed to developed
silver) was thereby introduced into the developing tank. Speed, contrast
and maximum density of each processed film sheet were substantially the
same.
Similar results were obtained when 8.times. 10 sheets (80 sq. in.), 75%
exposed, were interposed between half exposed 20.times. 24 inch sheets.
Just as each 20.times. 24 inch, half exposed sheet was fed into the
processor the developer was replenished as previously described. Just as
each 8.times. 10 inch, 75% exposed sheet was fed into the processor, 10
milliliters of Part A, 10 milliliters of Part B and 40 milliliters of
water were metered, mixed and pumped into the developer. Speed, contrast,
and maximum density of each processed film sheet were substantially the
same.
EXAMPLE II
A direct positive film containing about 80 mole percent AgBr and about 20
mole percent of AgCl similar to that in Example I of Burt, U.S. Pat. No.
3,445,235 was cut into sheets 20.times. 24 inches. Ten sheets were exposed
as in Example I except that only 25 percent of each sheet was covered with
an opaque mask. Each exposed sheet was processed in developer as in
Example I except that in this instance Part B solution concentrate
contained no potassium bromide and the following replenishment procedure
was used. Thirty seconds after each exposed film sheet was fed into the
processor metering pumps were activated to meter 20 ml of Part A, 20 ml of
bromide free Part B and 80 ml of water into the mixing volume. One
milliliter mixed replenisher per square inch of unexposed positive film
area (developed silver) was pumped into the processor developing tank.
Speed, contrast and maximum density of each processed film sheet were
substantially the same.
EXAMPLE III
Five exposed lithographic film sheets (20.times. 24 inches) of Example I
and five exposed direct positive film sheets of Example II were processed
in developer as in Example I. In this instance three solution concentrates
were used, Part A of Example I, bromide free Part B of Example II and Part
C which was 5 g potassium bromide in water to make 0.1 liter. Just before
an exposed sheet of direct positive film was fed into the automatic film
processor Part A, Part B and water were metered, mixed and pumped into the
developer tank of the processor as in Example II. Just before a sheet of
the lithographic film was fed into the processor 40 ml of Part A, 40 ml of
Part B, 4 ml of Part C and 156 ml of water were metered, mixed and pumped
into the processor developing tank. On sensitometric evaluation speed
contrast and top density of the direct positive film sheets were
essentially the same, and similarily, speed contrast and top density of
the lithographic film sheets did not substantially change. The order in
which the two types of film were processed did not appear to affect the
sensitometry.
EXAMPLE IV
An eight foot long, ten inch wide web of Lithographic film having a
composition similar to that of Example I was uniformly exposed for 2
seconds to a white light tungsten source. One end of the web was fed into
a LogEtronics Model LD/24 automatic processor containing the developer
solution of Example I. Solution concentrates Part A and Part B were
prepared as in Example I. Just as the leading edge of the web was fed into
the processor, metering pumps were actuated to meter 13 ml of Part A, 13
ml of Part B, and 52 ml of water directly into the processor developer
tank. As the web was being fed into the processor the metering pumps were
repetitively reactivated at 8 inch intervals (i.e., every 15 seconds for a
feed rate of 33 inches per minute) to meter 13 ml of Part A, 13 ml of Part
B and 54 ml of water into the processor developing tank. Density over the
length of the processed film web was substantially the same, i.e., 3.5 as
measured with a standard transmission densitometer.
EXAMPLE V
Developer solution (64 liters) with the following composition was prepared
and put in the developer tank of the LogEtronics LD/24 automatic
processor.
______________________________________
Hydroquinone 20 g
Ethylene glycol 70 g
Sodium formaldehyde bisulfite
42.5 g
Sodium sulfite 6 g
Sodium bromide 1.75 g
Sodium carbonate 12.5 g
Sodium bicarbonate 4.75 g
Trisodium ethylenediaminetetra-
acetate trihydrate 1 g
Sodium hydroxide 4.5 g
Sodium metaborate octahydrate
6 g
Water to make 1 liter
______________________________________
Replenisher solution concentrates were prepared having the following
composition:
______________________________________
Part A
Hydroquinone 170 g
Ethylene glycol 420 g
Sodium formaldehyde bisulfite
178 g
Water to make 1 liter
Part B
Sodium formaldehyde bisulfite
77 g
Sodium sulfite 40 g
Sodium carbonate 75 g
Sodium bicarbonate 28.5 g
Trisodium ethylenediaminetetra-
acetate trihydrate 6 g
Sodium hydroxide 27 g
Sodium metaborate octahydrate
36 g
Water to make 1 liter
Part C
Sodium bromide 6 g
Part B solution concentrate
1 liter
______________________________________
Lithographic film sheets, 20.times. 24 inches, were prepared and exposed as
in Example I. Just as each exposed sheet was fed into the automatic
processor metering pumps were activated to meter 40 ml of Part A, 40 ml of
Part C and 160 ml of water into a mixing volume from which the mixed
replenisher was pumped into the processor developer tank. Speed, contrast
and maximum density of each processed film sheet were substantially the
same.
Direct positive film of Example II was cut into sheets 8.times. 10 inches.
Each sheet was exposed as in Example I and fed into the automatic
processor. Just as each half-exposed sheet was fed into the processor
metering pumps were activated to meter 6.5 ml of Part A, 6.5 ml of Part B
and 27 ml of water into a mixing volume and pump the resulting mixed
replenisher into the processor developer tank. Sensitometry for each of
the exposed sheets was substantially the same.
EXAMPLE VI
Developer and solution concentrate Part A was prepared as in Example V.
Solution concentrate Part B was prepared from 1 liter of Part B of Example
V, 10.5 g sodium bromide and 60 g sodium sulfite. Speed and dot quality
obtained with the developer in Du Pont Cronalith 24L processor (developer
tank 75 liters) was immediately determined using the method described in
Example I of U.S. Pat. No. 3,622,330. Midtones, shadows and highlights of
the processed halftone strips were excellent. The processor was not used
for 16 hours, but developer temperature was maintained at 80.degree. F.
After this time, speed had dropped by about 10% and dot quality was
acceptable. The original speed and dot quality were restored by
replenishing the developer by activating the metering pumps to meter 330
ml Part A, 330 ml Part B, and 1340 ml of water into a mixing volume from
which the mixed replenisher was pumped into the developer tank.
Subsequently, every 2 hours a timer activated the pumps by which means 40
ml Part A, 40 ml Part B, and 160 ml of water were metered, mixed and
pumped into the developer tank. The same two prepared solution
concentrates were used for days until the reservoirs were near empty.
During this time replenishment based on use was carried out as described
in the previous Examples. Just before the reservoirs were refilled with
replenisher solution concentrates, speed and dot quality were determined
to be near the speed and dot quality of the original developer solution.
EXAMPLE VII
Lithographic film sheets, 20.times. 24 inches, were prepared, exposed and
processed as in Example I except that addition of replenisher was by the
following procedure. Part A was prepared by diluting Part A of Example I
with water to make 3 liters of solution. Part B was prepared by diluting
Part B of Example I with water to make 3 liters of solution. Just as each
half-exposed, 20.times. 24, lithographic film sheet was fed into the
processor 120 ml of Part A and 120 ml of Part B were metered into a mixing
volume from which the mixed replenisher was pumped into the processor
developer tank. Speed, contrast and maximum density of each processed film
sheet were substantially the same as that obtained in Example I.
EXAMPLE VIII
Developer solution concentrates were prepared having the following
composition:
______________________________________
Part 1
Hydroquinone 120 g
Ethylene glycol 420 g
Sodium formaldehyde bisulfite
178 g
Water to make 1 liter
Part 2
Sodium formaldehyde bisulfite
77 g
Sodium sulfite 12 g
Sodium bromide 10.5 g
Sodium carbonate 75 g
Sodium bicarbonate 28.5 g
Trisodium ethylenediaminetetra-
acetate trihydrate 6 g
Sodium hydroxide 27 g
Sodium metaborate octahydrate
36 g
Water to make 1 liter
______________________________________
Replenisher solution concentrates were prepared having the following
compositions:
______________________________________
Part A
Hydroquinone 50 g
Part 1 1 liter
Part B
Sodium formaldehyde bisulfite
77 g
Sodium sulfite 40 g
Sodium bromide 6 g
Sodium carbonate 75 g
Sodium bicarbonate 28.5 g
Trisodium ethylenediaminetetra-
acetate trihydrate 6 g
Sodium hydroxide 27 g
Sodium metaborate octahydrate
36 g
Water to make 1 liter
______________________________________
A supplementary solution concentrate was prepared having the following
composition:
______________________________________
Part C
Sodium bisulfite 23 g
Part 2 1 liter
______________________________________
Developer solution having the composition 1 liter Part 1, 1 liter Part 2
and 4 liters water was put in the developer tank (75 liters) of a Du Pont
Cronalith 24 L processor. Speed and dot quality was immediately determined
with the developer as in Example I of U.S. Pat. No. 3,622,330. Midtones,
shadows, and highlights of the processed halftone strips were excellent.
The processor was kept on but not used for two hours and developer
temperature maintained at 80.degree. F. At the end of the two-hour period,
0.5 liters of Part A, 0.5 liters of Part C, and 2 liters of water were
metered into the developer tank to maintain speed and dot quality at
substantially their original values. During the second two hours several
exposed sheets of lithographic film similar to that in Example I of
Nottorf, U.S. Pat. No. 3,325,286 were processed and the developer tank
replenished as in Example V. Thus, during this time period 83 ml of Part
A, 83 ml of Part B, and 332 ml of water were metered into the developer
to compensate for the film processed. At the end of the second two hours
417 ml of Part A, 417 ml of Part C, and 1668 ml of water were added to
the developer to maintain speed and dot quality at their original values.
During the third two-hour period a substantial amount of lithographic film
was processed and 0.52 liters of Part A, 0.52 liters of Part B, and 2.08
liters of water were added to the developer to compensate for the film
processed. Since the amount of replenisher, i.e., 0.52 1 of Part B, added
during this two-hour period exceeded the amount of supplementary solution
concentrate, i.e., 0.51 of Part C, needed to maintain developer activity
during a two-hour period of no use, no supplementary Part A and Part C was
added to the developer at the end of the third two-hour period. Speed and
dot quality obtained at the end of this third time period were found to be
substantially the same as the original values. The processor was operated
eight hours a day, five days a week for three weeks. During the time the
processor operated, film was processed intermittently with concurrent
replenishment by Parts A and B, and every two hours supplementary
replenisher Parts A and C was added to the developer when needed, i.e., ml
of Part C = 0.5 - ml Part B used during time period, ml Part A== ml Part
C, and ml water = 4 X ml Part C. During the three-week period developer
activity as measured by speed of processed film was maintained within
about 5% of the original value.
* * * * *
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