Film processing chemicals Flashcards by Christine Davis

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.

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What makes location of the darkroom important?

convenient for all modalities

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Why is the entrance of a dark room important?

Revolving door vs. maze (keeping light out while techs come and go)

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Why is it important that the darkroom be well ventilated?

Because chemicals are in use in a dark room.

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Why is it important that the dark room floor be free of clutter?

to avoid tripping in dark

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Why is it important to keep the darkroom floor free of spills?

To avoid slipping on the floor.

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What makes having counter tops free from clutter in the dark room important?

easier to maintain a dust free environment

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What does processing the film do?

Converts the invisible latent image into the visible manifest image

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What are the four steps of film processing?

developing, fixing, washing & drying.

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What is the processing cycle and how long does it take?

amount time to process single piece of film

45 seconds - 3.5 minutes

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What is the processor capacity?

the number of films processed per hour

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Most processing takes how long?

90 seconds.

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What is the main purpose of developing?

: turn exposed silver crystals into metallic silver

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This metallic silver left after developing is:

the radiographic density that makes up the image that we view

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Developer Solution consists of :

developing (reducing)agents
 accelerator (activator) agents	
 restrainer
 preservative
 hardener
 solvent

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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

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Developer or Reducing Agents:

reduce exposed silver halide to metallic silver also adds electrons to exposed silver halide

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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

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Hydroquinone

creates higher densities (black) – principal component

Acts slowly

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Phenidone and metol

creates lower densities (lighter shades of grey)

Acts fast.

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Together, hydroquinone and phenidone make up

the range of densities we see on the radiograph

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Synergism (Superadditivity):

chemicals produce greater effect when working together as opposed to working separately

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Hydroquinone & Phenidone are synergistic in quality in that they

work together.

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The synergistic action of hydroquinone and phenidone are what shape

the characteristic curve.

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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%

Film processing chemicals Flashcards

(79 cards)