Chapter 12 DarkroomProcedures. Darkroom Procedures n To repeat what was previously said about the composition of x-ray film, it has a base of cellulose.

Chapter 12Chapter 12

DarkroomDarkroom

ProceduresProcedures

Darkroom ProceduresDarkroom Procedures

To repeat what was previously said To repeat what was previously said about the composition of x-ray film, it about the composition of x-ray film, it has a base of cellulose acetate covered has a base of cellulose acetate covered on both sides with a sensitive emulsion on both sides with a sensitive emulsion of silver halides (silver bromide, of silver halides (silver bromide, chloride & iodide).chloride & iodide).

Today plastic polyester is used.Today plastic polyester is used.


When this emulsion is exposed to When this emulsion is exposed to radiation or light (from screens or other radiation or light (from screens or other sources) an unexplainable change takes sources) an unexplainable change takes place that cannot be seen.place that cannot be seen.

The change is produced in the physical The change is produced in the physical & chemical structure of the emulsion.& chemical structure of the emulsion.


The change produced on the emulsion The change produced on the emulsion depends upon the amount of x-ray & light depends upon the amount of x-ray & light reaching it.reaching it.

Since the body part being radiographed Since the body part being radiographed absorbs some of the radiation being directed absorbs some of the radiation being directed at it, we can see that the amount reaching at it, we can see that the amount reaching the screens & the film depends upon the the screens & the film depends upon the intervening tissue.intervening tissue.

Darkroom ProceduresDarkroom Procedures For example, bone absorbs more x-ray & fewer rays For example, bone absorbs more x-ray & fewer rays

get through to the film/crystals.get through to the film/crystals. Therefore, fewer crystals are activated.Therefore, fewer crystals are activated. The areas outside the parts receive the total amount of The areas outside the parts receive the total amount of

radiation & in this area structural change is complete.radiation & in this area structural change is complete. The portion of the film under the lead marker (and The portion of the film under the lead marker (and

any other structure that absorbs all the radiation) any other structure that absorbs all the radiation) receives none & there is no structural change to the receives none & there is no structural change to the silver halide crystals.silver halide crystals.


The other tissue areas absorb the x-rays in The other tissue areas absorb the x-rays in varying degrees depending upon the varying degrees depending upon the thickness & density of the parts & thus the thickness & density of the parts & thus the film & screens under these parts receive film & screens under these parts receive varying degrees of x-ray & the screens glow varying degrees of x-ray & the screens glow in varying degrees & thus the change in the in varying degrees & thus the change in the emulsion varies from place to place.emulsion varies from place to place.

A A Latent imageLatent image is formed in this way. is formed in this way.


We can therefore see that the latent We can therefore see that the latent image must be a complete one.image must be a complete one.

The purpose of dark room The purpose of dark room procedures is to change the latent procedures is to change the latent image to a photographic one.image to a photographic one.

Film Processing ChemicalsFilm Processing Chemicals

Various chemicals are used in the Various chemicals are used in the processing of the radiographic film.processing of the radiographic film.

Of the ones discussed here, the Of the ones discussed here, the developer & the fixer must be used; the developer & the fixer must be used; the developer replenisher, the fixer developer replenisher, the fixer replenisher & the acid stop-bath may replenisher & the acid stop-bath may or may not be used.or may not be used.

Film Processing ChemicalsFilm Processing Chemicals

There are other chemicals used for There are other chemicals used for special purposes (intensification of special purposes (intensification of under-developed film, reduction of under-developed film, reduction of over-developed film), but they will not over-developed film), but they will not be discussed.be discussed.

Directions for their use will be found Directions for their use will be found on the package.on the package.

The DeveloperThe Developer

Developing is actually the reduction of Developing is actually the reduction of the exposed silver halides to metallic the exposed silver halides to metallic or elemental silver (the converting of or elemental silver (the converting of the latent image to a visible image).the latent image to a visible image).

The developer causes a reaction of the The developer causes a reaction of the silver halide crystals & thus makes silver halide crystals & thus makes them visible.them visible.


This is done through a pair of redox This is done through a pair of redox reactions where an electron is made reactions where an electron is made available to unite with a silver ion available to unite with a silver ion that has a single (+) charge (from that has a single (+) charge (from light hitting the film), thus reducing light hitting the film), thus reducing the silver ion to metallic/elemental the silver ion to metallic/elemental silver.silver.

The DeveloperThe Developer Reducing AgentsReducing Agents

– change the exposed silver halides to black metallic change the exposed silver halides to black metallic silver; elon (for detail) is balanced with hydroquinone silver; elon (for detail) is balanced with hydroquinone (for contrast).(for contrast).

Accelerator/ActivatingAccelerator/Activating– maintains the proper alkalinity for the developer to maintains the proper alkalinity for the developer to

work & also swells the gelatin. Accelerating agents work & also swells the gelatin. Accelerating agents include sodium carbonate or sodium hydroxide.include sodium carbonate or sodium hydroxide.

Prolonged exposure to these may result in Prolonged exposure to these may result in dermatitis due to its alkalinitydermatitis due to its alkalinity


PreservativePreservative– prevents oxidation of the developing agents by prevents oxidation of the developing agents by

having a greater affinity for Ohaving a greater affinity for O2 2 than the than the developing agents themselves. The preservative developing agents themselves. The preservative used is sodium sulfite.used is sodium sulfite.

RestrainerRestrainer– slows down the development rate in order to slows down the development rate in order to

prevent fogging. Potassium bromide & prevent fogging. Potassium bromide & potassium iodine are the agents used.potassium iodine are the agents used.


Dissolving AgentDissolving Agent– used is water.used is water.

Hardening AgentsHardening Agents– used in automatic processors & used in automatic processors &

functions to prevent excessive functions to prevent excessive emulsion swelling. These agents emulsion swelling. These agents include gluteraldahyde.include gluteraldahyde.

The Developer ReplenisherThe Developer Replenisher

In using the developer the bromide In using the developer the bromide removed from the film builds up & acts as removed from the film builds up & acts as a restrainer for prolonged developing time. a restrainer for prolonged developing time. Developer replenisher, which is a Developer replenisher, which is a supercharged developer with no restrainer, supercharged developer with no restrainer, can be added to the developer tank to bring can be added to the developer tank to bring the solution up to a proper level while also the solution up to a proper level while also bringing it back to its proper strength.bringing it back to its proper strength.

The Acid Stop-BathThe Acid Stop-Bath

This is absent in all automatic processors This is absent in all automatic processors as the rollers within the processor as the rollers within the processor function to squeeze off the developer.function to squeeze off the developer.

In manual developing, the acid stop-bath In manual developing, the acid stop-bath can be used after the film leaves the can be used after the film leaves the developer to stop the development developer to stop the development immediately.immediately.

The Acid Stop-BathThe Acid Stop-Bath

It is a weak acetic acid solution that It is a weak acetic acid solution that neutralizes the alkaline developer.neutralizes the alkaline developer.

Acid stop-bath is not usually used Acid stop-bath is not usually used because it necessitates having an extra because it necessitates having an extra tank. The film is usually rinsed in the tank. The film is usually rinsed in the water tank to remove most of the water tank to remove most of the developer before putting it into the fixer.developer before putting it into the fixer.

The FixerThe Fixer Fixation involves two separate processes:Fixation involves two separate processes:The “clearing” of the film of unexposed silver The “clearing” of the film of unexposed silver

halide salts which are not affected by the halide salts which are not affected by the developer &which would turn black if developer &which would turn black if exposed to light (these have not been reduced exposed to light (these have not been reduced by the developer).by the developer).

The “hardening” of the emulsion.The “hardening” of the emulsion.

The FixerThe Fixer The darkroom lights may be turned on as soon The darkroom lights may be turned on as soon

as the film has cleared since there are than no as the film has cleared since there are than no light sensitive elements in the emulsion.light sensitive elements in the emulsion.

Clearing AgentClearing Agent– removes the unexposed silver halide salts from removes the unexposed silver halide salts from

the film (sodium thiosulfate, a.k.a. hypo). Most the film (sodium thiosulfate, a.k.a. hypo). Most modern fixers use ammonium thiosulfate.modern fixers use ammonium thiosulfate.

The FixerThe Fixer

HardenerHardener– reduces the swelling & softening of the reduces the swelling & softening of the

emulsion produced by the alkaline emulsion produced by the alkaline developer & hardens it (potassium alum).developer & hardens it (potassium alum).

PreservativePreservative– maintains proper acidity of the solution & maintains proper acidity of the solution &

prevents early breakdown of the clearing prevents early breakdown of the clearing agent (sodium sulfite).agent (sodium sulfite).

The FixerThe Fixer

AcidifierAcidifier– neutralizes the alkaline developer neutralizes the alkaline developer

carried over & keeps the medium acid carried over & keeps the medium acid for the hardener to do a full job (acetic for the hardener to do a full job (acetic or sulfuric acid).or sulfuric acid).

Dissolving AgentDissolving Agent– used is water.used is water.

The FixerThe Fixer

In manual developing chrome alum In manual developing chrome alum may be used as a hardener instead of may be used as a hardener instead of potassium alum.potassium alum.

This makes the fixer opaque to light.This makes the fixer opaque to light. Therefore, the lights may be turned on Therefore, the lights may be turned on

as soon as the film is put into the fixer as soon as the film is put into the fixer with out harm.with out harm.

The Fixer ReplenisherThe Fixer Replenisher

Replenisher for the fixer is Replenisher for the fixer is available but care must be taken to available but care must be taken to remove enough of the old solution remove enough of the old solution before adding the replenisher for before adding the replenisher for solution carried out must be solution carried out must be balanced by solutions carried in.balanced by solutions carried in.

Steps in Film ProcessingSteps in Film Processing

Before beginning to process film the developer Before beginning to process film the developer & fixer should be stirred with separate paddles.& fixer should be stirred with separate paddles.

The temperature should be as close to 68The temperature should be as close to 6800 as as possible.possible.

Developing times & temperatures may vary.Developing times & temperatures may vary. As a rule with increased temperature you As a rule with increased temperature you

decrease the developing time & vice versa. decrease the developing time & vice versa.


The film is removed from the The film is removed from the cassette & clipped into a film cassette & clipped into a film hanger. hanger.

The cassette should be closed to The cassette should be closed to avoid staining of the screens with avoid staining of the screens with solutions during processing.solutions during processing.

Steps in Film ProcessingSteps in Film Processing The film is than passes through the The film is than passes through the

following five steps (four with automatic following five steps (four with automatic processing):processing):

DevelopingDeveloping RinsingRinsing FixingFixing WashingWashing DryingDrying

Steps in Film ProcessingSteps in Film Processing DevelopingDeveloping

– developing of the film may be done by:developing of the film may be done by:

1) sight (under a safelight of course)1) sight (under a safelight of course)

2) by time & temperature charts 2) by time & temperature charts which are available.which are available.

– The average time developing temp/time The average time developing temp/time is 68is 6800 for 5 minutes. for 5 minutes.

Steps in Film ProcessingSteps in Film Processing Time & temperature is recommended because the Time & temperature is recommended because the

opacity of the uncleared film & the length of time opacity of the uncleared film & the length of time for the eye to accommodate to the darkness makes for the eye to accommodate to the darkness makes inspection of the film difficult & prolonged inspection of the film difficult & prolonged exposure to the safelight can fog the film.exposure to the safelight can fog the film.

In either case the film should be agitated for the In either case the film should be agitated for the first few seconds in the developer to remove any first few seconds in the developer to remove any air bubbles on the film surface that would restrict air bubbles on the film surface that would restrict development in that area. development in that area.

Steps in Film ProcessingSteps in Film Processing RinsingRinsing

– After development the film should be rinsed in clear After development the film should be rinsed in clear water (running) for 30 to 45 seconds to remove as much water (running) for 30 to 45 seconds to remove as much of the developing chemicals as possible to stop of the developing chemicals as possible to stop development & prevent contamination of the fixer with development & prevent contamination of the fixer with alkaline developer.alkaline developer.

– An acid stop-bath may be used in place of the rinse, but An acid stop-bath may be used in place of the rinse, but in using either the film should be drained before putting in using either the film should be drained before putting it into the fixer.it into the fixer.

In automatic processing the rinsing stage is In automatic processing the rinsing stage is removedremoved


FixingFixing– We have previously described the actions of the We have previously described the actions of the

fixer as “clearing” & “hardening” of the fixer as “clearing” & “hardening” of the emulsion. These two processes occur emulsion. These two processes occur simultaneously but the latter takes simultaneously but the latter takes approximately twice as long.approximately twice as long.

– The clearing time is usually 3-4 minutes but the The clearing time is usually 3-4 minutes but the film is left in the fixer for 10 minutes for film is left in the fixer for 10 minutes for hardening.hardening.


WashingWashing– The finished film should be composed of The finished film should be composed of

metallic silver embedded in gelatin & nothing metallic silver embedded in gelatin & nothing else. The film must be thoroughly washed to else. The film must be thoroughly washed to remove all chemicals to prevent discoloration & remove all chemicals to prevent discoloration & fading of the image.fading of the image.

– Films should be washed 15 minutes in clear Films should be washed 15 minutes in clear running water, depending upon the rate of flow, running water, depending upon the rate of flow, temp., type of film used & the type of fixer used. temp., type of film used & the type of fixer used.


The longer the film spends in the The longer the film spends in the fixer, the longer the wash time fixer, the longer the wash time needed.needed.

This is a 1:2:3 ratio of This is a 1:2:3 ratio of developer to fixer to wash.developer to fixer to wash.

Steps in Film ProcessingSteps in Film Processing DryingDrying The ideal situation for drying of x-ray film is a The ideal situation for drying of x-ray film is a

film drying box that combines a heating film drying box that combines a heating element with a circulating fan. It can dry in 15 element with a circulating fan. It can dry in 15 minutes.minutes.

Film will dry properly if hung in air for a Film will dry properly if hung in air for a longer period (1+ hours).longer period (1+ hours).

A fan aimed at the edge of the film will speed A fan aimed at the edge of the film will speed up the process.up the process.

Replenisher Method & Exhaustion MethodReplenisher Method & Exhaustion Method

Both the developer & the fixer may be Both the developer & the fixer may be either replenished to maintain the timing either replenished to maintain the timing or used until exhausted by increasing the or used until exhausted by increasing the time element.time element.

Both methods are satisfactory but the Both methods are satisfactory but the replenisher method saves time, does not replenisher method saves time, does not involve record keeping & is less involve record keeping & is less expensive. expensive.

Chapter 12 DarkroomProcedures. Darkroom Procedures n To repeat what was previously said about the composition of x-ray film, it has a base of cellulose.

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