Film processing chemicals Flashcards
What is a darkroom?
A place where handling & processing of film can be carried out safely & efficiently w/out hazard of producing film fog by accidental exposure to light or x rays.
What makes location of the darkroom important?
convenient for all modalities
Why is the entrance of a dark room important?
Revolving door vs. maze (keeping light out while techs come and go)
Why is it important that the darkroom be well ventilated?
Because chemicals are in use in a dark room.
Why is it important that the dark room floor be free of clutter?
to avoid tripping in dark
Why is it important to keep the darkroom floor free of spills?
To avoid slipping on the floor.
What makes having counter tops free from clutter in the dark room important?
easier to maintain a dust free environment
What does processing the film do?
Converts the invisible latent image into the visible manifest image
What are the four steps of film processing?
developing, fixing, washing & drying.
What is the processing cycle and how long does it take?
amount time to process single piece of film
45 seconds - 3.5 minutes
What is the processor capacity?
the number of films processed per hour
Most processing takes how long?
90 seconds.
What is the main purpose of developing?
: turn exposed silver crystals into metallic silver
This metallic silver left after developing is:
the radiographic density that makes up the image that we view
Developer Solution consists of :
developing (reducing)agents accelerator (activator) agents restrainer preservative hardener solvent
Developing has two purposes while converting latent image to manifest image:
1) amplify amount of metallic silver on film
increases number of silver atoms in latent image center
2) reduce exposed silver halide crystals into metallic silver
Developer or Reducing Agents:
reduce exposed silver halide to metallic silver also adds electrons to exposed silver halide
Developer gives electrons to
sensitivity specks in emulsion of film
Electrons attract silver to these areas
amplifies amount of silver
Exposed silver halide reduced to metallic silver
Hydroquinone
creates higher densities (black) – principal component
Acts slowly
Phenidone and metol
creates lower densities (lighter shades of grey)
Acts fast.
Together, hydroquinone and phenidone make up
the range of densities we see on the radiograph
Synergism (Superadditivity):
chemicals produce greater effect when working together as opposed to working separately
Hydroquinone & Phenidone are synergistic in quality in that they
work together.
The synergistic action of hydroquinone and phenidone are what shape
the characteristic curve.
Optical density is the result of:
reducing agents.
The Characteristic Curve is a graph of
the optical density
The Characteristic Curve shows the relationship between
the exposure to a film and the amount of light that can be transmitted through that film
The Characteristic Curve is shaped by
the action of the developing agents
Phenidone is responsible for the toe
Hydroquinone is responsible for the shoulder of the curve
Also in the developer is a wetting agent :
water, to soften and swell the emulsion
Accelerator/Activator Agents are also called:
buffering agents
Accelerator/activator agents elevate and maintain:
the pH of the developer.
pH measures:
the alkalinity of solution needed for the reducing agents and Enhances action of reducing agents by maintaining the developer solution in alkaline state
Loss of pH =
loss of developer activity
Example of a Buffering agent
Sodium Carbonate.
Restrainer:
Decreases the reduction or development of unexposed silver halide
Keeps unexposed crystals from the developing agent
Without restrainer the crystals that were not exposed
would still be reduced to metallic silver. This would result in development fog
development of unexposed silver halide
Example of restrainer:
Potassium Bromide
Preservative:
Preserves the developer by decreasing oxidation of the developer solution
Aerial oxidation
reduction in chemical activity of developer by air. Air above the tank takes as many electrons as it can grab from the developer.
The presence of a float on top of the solution in the developer replenisher tank is to
retard aerial oxidation.
Use oxidation
reduction in chemical strength as result of increased temperature over period of time
By controlling oxidation the preservative maintains
proper development rate
Example of preservative:
Sodium Sulfite
Hardener
Hardens emulsion which was originally softened by reducing agents & Protects the image on film from action of rollers
Example of hardener:
Glutaraldehyde
Insufficient hardener leaves
gelatin on rollers.
Gelatin on rollers causes:
transport problems.
Biggest problem in automatic processing is
insufficient Glutaraldehyde
The hardener helps ensure
Archival Quality
Solvent:
Water. Dilutes chemicals in developer solution
Helps stop chemicals from over acting
Helps chemicals to function at their best level of activity
Film development is simply a chemical reaction affected by:
Time
Temperature
Concentration of developer
Any deviation from any of these will reduce or degrade image quality
Increasing the development time will
increase reduction of silver and produce an image that is too dark
If the temperature is too high the results will be
too dark
If develop concentration is too strong the reducing agents will
be too powerful and will affect exposed and unexposed silver halide crystals
A change in time, temperature or concentration of developer, from the manufacturer’s recommendation will result in
fogging the film. Image will appear gray and lack sufficient contrast
Fog can also be produced by
chemical contamination of the developer known as Chemical Fog
Fixing:
Removes unexposed silver halide and makes the remaining image permanent
Fixer consists of :
activator (acidifier) fixing (clearing) agent preservative hardener solvent
Acidifier/Activator:
Neutralizes the pH of emulsion and stops action of developer
Similar to a stop bath
example of Activator:
Acetic Acid
Clearing (Fixing) Agent:
clears undeveloped silver halide from film. Also known as “hypo.”
Hypo retention
the retention of fixer left in emulsion.
Hypo retention causes:
browning of the film.
Silver sulfide stain most common cause of
poor archival quality
Example of fixer:
Ammonium Thiosulfate
Preservative:
Protects the fixing agent from oxidation
Maintains chemical balance due to carryover of developer to fixer tank
What does Sodium Sulfite do and what is it an example of?
Helps dissolve silver from ammonium thiosulfate so will continue to remove silver from emulsion. Its an example of a preservative.
Second application of hardener:
Further hardens the emulsion so that the image becomes a permanent record and makes it better for handling. Causes emulsion to harden to aid in transport through washer & dryer
Ensures quick & complete drying
Prevents scratches & abrasions
Example of second hardener:
Potassium aluminum***
Aluminum chloride – chromium alum
Washing:
Removes fixer and developer solution from surface of film
Prevents browning and fading over time.
Temperature of wash should be:
5 degrees F or 3 degrees C lower than the other solutions.
If the temperature of the wash is too drastic of a change:
fast the emulsion may crack into many pieces (reticulation)
Drying:
Final process
Forced hot air over both sides of film
Temperature ranges from 120 - 150°F (43-65°C)
Remove 85% - 90% of moisture
Retains some moisture as to prevent cracking
Sets final hardening to emulsion
Seals supercoat
Manuel processing requires how much time from start to finish?
Over one hour.
Automatic processing requires how much time from start to finish (dry to drop time)?
90 seconds.
How long is a radiograph stored?
5-7 years.
How long is a mammography radiograph stored?
10 years.
What is the storage temperature of radiographs?
70 degrees F (23 degrees C)
At what humidity should radiographs be stored?
60%
