Film Processing (5) Flashcards
Five steps of manual film processing:
- development
- stopping the development/pre-wash
- fixing
- washing
- drying
Describe the Development process
Developing agent gives up electrons to convert silver halide grains to metallic silver.
- exposed grains develop rapidly, with enough time convert silver ions to silver metal.
- requires proper temp
Chemicals that make up developer:
- Metol and hydroquinone (convert silver halide to black metallic silver)
- Sodium Carbonate (accelerate)
- Sodium sulphate (preservative, reduce oxidation)
- Potassium bromide or potassium iodide (ensure reduction of exposed grains only/restrainer)
- wetting, softening and anti-swelling agents (improve developer quality and lifespan)
The rate of development is affected by the ____ of the solution.
temperature of the solution.
- as temperature rises, rate of development increases
What is the most common developer temperature?
20°C or 68°F
How are temperatures maintained in manual tanks?
immersion heaters/chill-chasers or heating elements (coils) around tank exteriors
What is the average concentration of liquid developer?
10 litres per 40 litre tank of clean water.
How can we monitor the activity of a developer?
test films, exposed under standard conditions. densities of exposures are measured and compared to densities of original exposures to determine any noticeable loss of gain in chemical activity.
A loss in developer activity would result in a ____ in density values.
reduction in density values.
Increase density = increased activity, decreased density = decreased activity.
What is the frequency of agitation in developer?
5-10 seconds for every minute f development.
What is the Stop Bath’s purpose?
Deactivate the developer in the emulsion before the film goes into the fixer bath.
What is the stop bath mixture made of?
25ml glacial acetic acid per litre of clean water
What is the purpose of Fixing?
- Remove all undeveloped silver salt on the emulsion, leaving only the developed silver image.
- harden gelatin for subsequent drying
Define “clearing time”
time interval between fixing the film and the disappearance of the original yellow “milkiness”.
- fixer is dissolving undeveloped halide crystals
Total fixing time should be longer than the clearing time by ____ to ___ times.
2 to 3 times
What temperature should the fixer be held at?
18-24°C
Clearing time checks: once clearing times begin to exceed ___ to ___ minutes the original clearing time, it is time to ___ the fixer bath.
10 to 12 minutes of the original clearing time, it is time to change the fixer bath.
Fixing time and agitation time:
no longer than 15 minutes
agitate every 1-2 minutes
Describe Clearing time checks
performed regularly
- unexposed film in fixer solution and then observed .
- time required to remove silver is recorded and minimum fixing time is established (2-3X clearing time)
Fixer solution mix:
10L solution per 40L water filled tank
Chemicals that make up fixer:
- potassium alum (hardening agent)
- organic acid (neutralizer)
- sodium sulphate (preserve)
- salt buffer
- Hypo-clearing agent (solvent)
Hourly rate of flow for a wash tank:
4-8x the volume of the wash tank
What is the purpose of washing?
remove any remaining chemicals after the fixing
Times and temperatures for washing
washed at minimum 20 minutes in non-circulated water (constant agitation required)
18-21° C not >25°C or <15°C
What is the purpose of a wetting agent?
Reduce drying times and possibility of water marks.
done by reducing surface tension
What is a wetting agent?
Photo-flow
also use jetdry or dish soap
100ml per 40L of water
How long is film immersed in a wetting agent?
10 seconds prior to drying
Describe the drying process:
- dry warm (28-48°C)
- do not prolong drying! can lead to brittleness, burns, melts
- circulated air
- built-in-fans, filters, heaters, desiccants
Four steps of automatic film processing:
- development
- fixing
- washing
- drying
Production time using an automatic film processor increase by:
10x
1.5 to 15 minutes
Parts of an automatic processor:
- feed system/tray
- transport system
- auto replenishment
- temp control
- agitation system
- constant flow/wash system
- high-flow air system
Advantages of automatic processing
- higher more consistent quality
- increase production
- no contact (reduced change of spillage)
- requires less space
Disadvantages of automatic processing
- cost
- long warm up time
- maintenance
- back up incase of failure
