This document provides information on dark room and film processing techniques. It discusses the key components and functions of a dark room for handling radiographic films without light exposure. It also describes the various stages of film processing including development, fixing, washing and drying. Both manual and automatic processing techniques are covered, outlining the different steps, equipment, chemical solutions and factors involved in each method. Automatic processors provide controlled, consistent processing using chemical tanks and a transport system to move films through development, fixation, washing and drying cycles.
2. Dark room
It is a facility where handling and processing of films can be carried out without
the hazard of producing fog by accidental exposure to light or x-rays.
It must exclude all outside light and provide “SAFE” artificial light
3. It should be in close proximity to the place where the work of radiographer is carried out.
It should serve as many imaging rooms as geographically possible.
4. Location
It should be centrally sited and served by
hatches(passboxes) from the adjacent imaging rooms.
Away from damp and hot areas
Power and water accessibility
Adjoining viewing area where processed films can be
checked or sorted out
5. Dark room
SIZE
Minimum floor area of 10m2
Ceiling height 2.5-3m
RADIATION PROTECTION
Coating the walls with barium plaster or increase the thickness
Lining the doors with LEAD ply-sheet
Shielding any gaps around the door
6. Dark Room
FLOORS
Durable and easy to maintain(Eg: Plastic tiles)
Non porous non slip flooring material
WALLS/CEILING
Light in color
Easy to wipe over and keep clean
7. Dark room
VENTILATION AND HEATING
Satisfactory working condition for staff
Good film handling and storage conditions
This can be ensured by
Relative humidity : 40-60%
Min of 10 air changes per hour
Room temperature 18-200C
13. WHITE LIGHTING
It is necessary for
Inspection and maintenance of cassettes and screens
Cleaning of work surfaces and floors
Servicing of equipment
White light should be
Close to the ceiling to avoid shadows
Moderate in intensity (60W tungsten /30Wfluorescent)
Centrally placed
14. SAFELIGHTING
Need: Working in compete darkness all day long is not a pleasant condition to
work on.
White light cannot be used as it causes fogging of film.
Hence DIM COLORED LIGHTING sufficient enough to work at is used
BUT THERE IS NO TOTALLY SAFE “SAFE”LIGHTING
15. How does a safelight filter work
Its about choosing a filter which will transmit a color to which
the film is relatively unresponsive while stopping all light to
which the film is most sensitive.
16. WHY SAFELIGHTING IS NOT 100% SAFE
No Filter completely absorbs the undesirable wavelengths
All films have SOME sensitivity to all wavelengths
HOW TO MAKE IT MORE SAFER?
Reduce the film handling time and intensity of illumination
Recommended Standard : 25w lamp sited at a minimum of 1.2m from the film
18. SAFELIGHTING
Areas where safe light is required
Film loading / unloading areas.
Processor film feed-in points.
Path b/w above two.
At developer tank.
19. SAFELIGHTING
Type/prop
Direct
Indirect
Mixed
Construction
Filter forms the undersurface
Filter forms the upper surface
Filters on both its upper and lower surfaces
Working
Directs light towards the floor
Directs light towards the ceiling
Directs light towards both floor and ceiling
Function
For film loading and unloading areas
For general illumination of the darkroom
For both the purposes
20. SAFELIGHTING
Safelight handling time
Maximum time a film can be exposed to safelight during the procedure without
causing any appreciable degree of fogging.
Average time : 20-45secs
Faster films need shorter time
21. DARK ROOM
Equipment and arrangement
An automatic processor
Cassette hatches
Film storage hopper
Loading bench/cupboards
24. PROCESSING CYCLE
Stage 1: DEVELOPMENT
The primary function of development is to convert the latent image into a
manifest or visible image
Secondary purposes of development.
To amplify the amount of metallic silver
To reduce the exposed silver halide crystal into metallic silver.
26. DEVELOPING SOLUTION
DEVELOPING AGENT
Principal component is hydroquinone (produces black tones slowly).
Secondary constituent is phenidone or metol (produces shades of grey rapidly).
Advantage of PQ developer:
adequate activity
high selectivity
super-additivity (oxidised phenidone is reduced by hydroquinone)
27. DEVELOPING SOLUTION
ACCELERATOR/ACTIVATOR/BUFFERING AGENT
Alkaline medium for the action of PQ-accelerates the developing process
KCO3 or KOH
Ideal range of pH: 9.8-11.4
RESTRAINER/Anti-foggant
It reduces converting unexposed AgX to Ag and thus prevent chemical fogging.
KBr, benzotriazole(used with PQ developer)
28. DEVELOPING SOLUTION
PRESERVATIVE
It reduces the oxidation of developing agents.
Eg: Potassium sulphite
HARDENER
It controls gelatin swelling to minimize risk of physical damage.
Eg:Glutaraldehyde
29. DEVELOPING SOLUTION
SEQUESTERING AGENT
Prevents the precipitation of insoluble mineral salts which occur in hard water
areas
EDTA containing compounds are used
SOLVENT
Carrying medium for dissolving the developer constituents
Softens the film emulsion gelatin
MC used : Tap water
30. FACTORS AFFECTING DEVELOPMENT
Temperature of the developing solution
Total time of the development
An adequate combination of both is important for complete development
31. TEMPERATURE FOR DEVELOPMENT
Optimum temperature is 20-22oC
Below 16oC, action of hydroquinone ceases
◦ Radiograph lacks contrast and density
◦ Can be compensated by increasing the developing time.
Above 24oC (too warm) emulsion softens.
◦ Chemical fog results
32. DEVELOPMENT TIME
Time interval which elapses between the entry of a specified part of a film into
the developing solution and its exit.
Short processing times reduce waiting times.
33. FACTORS DETERMINING DEVELOPMENT
TIME
Developer activity- Active developer achieves given image density more
rapidly.
Type of film emulsion- Thick emulsion film > thinner ones(non screen
type>screen type film)
Agitation- Proper agitation fasten the development process.
34. STAGE 2:FIXING
During development not all the silver halides are reduced. Only 40% get
reduced
The remaining silver halides greatly impairs the
usefulness and permanence of the developed
radiograph and hence have to be removed.
35. FIXATION
It has four major functions
Stop any further development
Makes the solution more acidic
Remove the unexposed AgX from the emulsion
Convert it to soluble compounds and remove it
Makes the image chemically stable and no longer photosensitive
Completes the process of hardening of emulsion
Minimizes water absorption and reduces drying time
36. FIXER SOLUTION
FIXING AGENT
The fixing agents by forming water soluble complexes
tightly binds the silver ions and removes them from
the solution.Eg: sodium thiosulphate(HYPO)
Silver bromide +sodium thiosulphate
Silver thiosulphate complex +Sodium bromide
37. FIXER SOULTION
ACIDIFIER
To stop the development process. Create an acidic pH environment for fixing
agent.
Eg-Acetic acid
PRESERVATIVE
To protect the fixing agent from oxidation and to maintain its activity, - Sodium
Sulfite
38. HARDENER
To further harden the emulsion to make the resultant image permanent. Al salt
such as Al sulphate, Al chloride.
SOLVENT
The purpose is to dilute the chemicals in the fixer solution – so that the
chemicals can function at their desired level of activity. Water
39. STAGE 3 : WASHING
Purpose of washing is to remove fixing solution from the surface of the film.
If the film is not properly washed, it will show a brown staining caused by
thiosulfate (fixing agent that remains in the emulsions).
The process by which washing works is diffusion.
Tap Water is mainly used
40. STAGE 4 : DRYING
Purpose is to remove 85-90% of the moisture from the film.
If film is dried excessively, emulsion can crack which decrease the diagnostic
quality.
41. TYPES OF FILM PROCESSING
AUTOMATIC
1- Unloading the film
2- Inserting into processor
MANUAL
1-Unloading the film
2-Loading the film onto a hanger
3-Development
4-Rinsing or stop bath
5-Fixing
6-Washing
7-Immersion in a wetting agent
8-Drying
43. AUTOMATIC PROCESSOR
Consists of chemical tanks, a roller transport system and a dryer system for the
processing of radiographic film.
Processing time -amount of time taken to process a single piece of film-90-115s.
Processor capacity – No.of film that can be processed per hour based on which
its divided into high and low.
44. AUTOMATIC PROCESSOR
Tanks
1. For Developer solution
2. Fixer solution
3. Wash tank for water
During a 90s processing cycle
Developer------ 26s
Fixer ----- 15s
Wash ----- 15s
Drier ------ 24s
Travel time----- 10s
45. SUBSYSTEMS OF AN AUTOMATIC
PROCESSOR
Transport
Temperature control
Replenishment
Recirculation
Wash
Drying
46. TRANSPORT SYSTEM
It ensures that the film moves through developer , fixer , wash and dryer at a
controlled and consistent speed without damage
Mainly 3 roller assemblies
1)Entrance roller
2)Transport roller
3)Turn around roller
47. CYCLE OF EVENTS
Drive motor energized(to turn the rollers)
Safelight above the feed tray extinguished
Developer and fixer replenisher pumped into tanks
Drier heater energized
Wash water flow rate boosted
Film signal delay time activated
But how does it get triggered ?
50. MOTOR DRIVE
An electrical motor provides power for the roller
assemblies to transport the film through the processor.
REPLENISHMENT SYSTEM
Function of replenishment system is replacement of fresh
chemicals after the loss of chemicals during processing -
specifically developer and fixer solution.
51. OVER REPLENISHMENT
Of developer solution causes an increase in radiographic density and decrease
in radiographic contrast.
Of fixer solution – no effect on radiographic quality.
UNDER REPLENISHMENT
Of developer can cause decreased density.
Of fixer – result in poor archival quality of finished radiograph
52. RECIRCULATION SYSTEM
To maintain solution activity and the required agitation. Also, to maintain proper
temperature of the developer solution.
Temperature control
If the temperature in developer tank
Raises increases the density.
DropDecreases the density.
53. WASHING
SPRAY WASH
By the help of processors situated in between the transport roller.
Water flow rate could be as high as 10 L/min
TANK IMMERSION
Water fed in to the tank by developer/heat exchanger.
Water flow rate is between 4-7L/min
54. DRYING SECTION
Initial drying happens when the film moves through the squeegee rollers
between the wash and drying section
While in drying section , it is commonly dried by
1 Hot air drying
2 Infrared drying.
58. MANUAL PROCESSING
1-Unloading the film
2-Loading the film onto a hanger
3-Development
4-Rinsing or stop bath
5-Fixing
6-Washing
7-Immersion in a wetting agent
8-Drying
Four Compartment tank – Developing, rinsing, fixing, and washing.
61. MANUAL PROCESSING
DEVELOPING
It is done by time – temperature technique
Here film is immersed in developer for 4 minutes
Temperature is maintained at 20 C
At intervals with in 4 minutes film is examined under safelights
If image seems to lack expected density at 4 minutes, development is
continued
62. MANUAL PROCESSING
RINSING
Purpose is to slow the action of developer and to remove it from the surfaces of
the film, done by a plain rinse bath.
To stop the action of developer, done by acid stop bath.
FIXING
After rinsing, the film is immersed in fixer solution
Fixing time can be up to 5 minutes
63. MANUAL PROCESSING
WASHING
Immerse the film in large tank or in a series of tanks through which water is kept
flowing.
Time duration:- 20 – 30 minutes
DRYING
Hot air drying cupboards or by rapid drier machines.
Temperature may vary from 40-50 C
64. COMPARISON
MANUAL
• DEVELOPING TEMP 200 c
• FIXING TEMP 200 C
• WASHING TEMP 200 C
• DRYING TEMP 430 C
• DEVELOPING TIME 3-5 MIN
• FIXING TIME 2-10MIN
• WASHING TIME 15-30MIN
• DRYING TIME 15-20MIN
• SURFACE CHANGE- MANUAL
• REPLENISHMENT - MANUAL
AUTOMATIC
• 350 C
• 350 C
• 350 C
• 570 C
• 25s
• 21s
• 9s
• 20s
• TRANSPORT ROLLER
• AUTOMATIC
No windows and only air conditioning and exhaust only if feasible
Inexpensive and economical , link electronically the door locking mechanism with lighting circuitthus preventing the door from being openend wen the safe lights are on
2 parallel passages with a facing wall.
Adv: easy ans instant access all times
Disadv: requires more area
Involves a metal cylinder wre we step in and manually rotate to gain entry to the darkroom
Adv: doesnot require a large area for installation.
When white light pass through , ceratin colors are absorbed by the filter while those corresponding to the the color of the filter will be transmitted.
Choose a filter for which the film is relatively unresponsive and stopping lights to which the film is most sensitive
Csette hatch: easy transport of films b/w radiograph room and darkroom
Hopper: unexposed films kept for immediate use in reloading casettes
Loading bench: ample working space and generous cupboard space
Phenidone:quick but develops all exposed agX,HQ is selective but less quick
High selectivity to act on latent image centre n thus produce low chemical fog.Adequate activity even in low conc.
Superadditivity is that,in presence of HQ effectiveness of PQ is increased by reducing t oxidized PQ n regenerating it..reducing effect of combn is more than sum of effects produced individually
Low ph : dvpin axn sluggish…hig ph –dvpr overactive and uncontrolled n chemical fogging
Restrainer inc the negative charge barrier around silver halide
Dvpin agents Combine with atm oxygen
Efficient regenrn of phenidone by hdroquinone
Gelatin normally swells In water.more pronounced in alkali dvping solution.
Soften to facilitate penetration of the developing chemicals
High temp developers in auto : 38-42
Low temp develpr: around 30degree
Med 33-37(most modern developers)
Agitation to remove the exhausted developer and its byproducts carried away rom the surface of the films
In manual processing there is RINSE before fixing which partially does the same
Preservative : prevents decomposition of thiosulphate thus ensuring its activity
Guide plate to change de direction by 90degree
Cross ovr :between tanks
Rollers are made either of rubber or PVC. Turn around needs rubber for better grip
Film seignal delay: audible signal sounding 1-3 s after the trailing edge of the film has passed to let the operator know tht the next film can be processed
Push the film in , the entry detector roller activates microswitches which sets in the train of sequence.Once the entire length has passed , it automatically switches off the microswitches
Film length and the width can be assessed based on the interrupted infraread beams thus to assess replenishment approporitae to film area
If dvpt happens in fixer- due to deposition of very fine siver particles