film screen 2

• WETTING


  • Swells the emulsion for better penetration
  • Use water, film put into water
  • Silver halide crystals react on solution
• DEVELOPING

  • Provides a visible image from latent image
  • Responsible for latent image to manifest
• STOP BATH

  • Terminates development and removes excess chemicals from emulsion
  • Automatic: no wetting agent manual:has wetting agent
• FIXING SOLUTION

  • Removes remaining silver halide crystals and hardens gelatin
• WASHING

  • Removes excess chemicals
  • If not washed properly - yellow brown color
• DRYING

  • Removes water and prepares film for viewing
  • Ready for interpretation and storing
• MANUAL PROCESSING

  1. Visual method

  2. Time-temperature method
• Visual method

  • Carried out in a darkroom with safelight conditions
  • An exposed x-ray film is immersed in the developing solution and periodically viewed under the safelight for the emergence of clear image
  • When the image appears, the film is washed and immersed in fixing solutions
• Time-temperature method

  • Effective standardization may be achieved without any automatic aids
  • Simple technique immersing the film in the developer kept at a constant temperature for a fixed duration of time
• MANUAL PROCESSING

  • Advantage: the action of development is under the direct control of the operator
  • Disadvantage: handling wet film, the requirement of a darkroom, and time consuming
  • Processing time: 1 hr
• AUTOMATIC PROCESSING

  • The exposed film is fed at one end and passes successively through the developer, fixer, water, and dryer
  • The roller system has a squeezing action; the developing solution is absorbed by the gelatin of the emulsion will be less as it is transported from developer to fixer
  • Makes use of roller system for the transport of film
  • The film comes out through the other end of the processor, processed, dry, and ready for viewing
  • Processing time: 90 sec or 1 1/2 min
• First automatic processor introduced by Pako

  1942 (early 1940s)
• First roller transport processor introduced by Eastman Kodak

  1956
• Kodak introduced dry-to-drop automatic processor

  1965
• Konica introduced 45 sec processing

  1987
• Today processors are available with processing time from 20-45 sec
• DEVELOPING

  Change the silver halide ions of the exposed crystals into metallic silver
• DEVELOPING AGENT

  • Also known as reducing agent
  • Hydroquinone - primary (contrast indicator)
  • Elone | Metol
  • Metol | Phenidone
  • Purpose: to reduce the exposed silver halide crystals chemically to black metallic silver
• PRIMARY COMPONENT OF REDUCING AGENT

  • Hydroquinone (Q developer)
  • Phenidone (P developer)
  • Synergism (superaddivity) - PQ
  • PQ - automatic processing
  • MQ - manual processing
• PHENIDONE

  • Rapidly reduces silver and enhances fine detail and subtle shades of gray
  • Not able to reduce heavily exposed area of an image
  • Replaces the function of metol (kodak brand name: elon) in manual process
  • Causes true increase in film speed
  • First to react
  • Speed indicator
• HYDROQUINONE

  • Slowly reduces silver and produces area of heavy density or the darkest shades
  • Ineffective at first but then rapidly increases in action
  • Sensitive to aerial oxidation
  • Contrast indicator
• OXIDIZED DEVELOPER

  • Brownish appearance
  • Because of aerial oxidation
• ACTIVATOR (ACCELERATOR/ALKALINIZER)

  • Action of reducing agents is enhanced by maintaining the developer solution in an alkaline state around pH 10.0-10.5
  • Sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide
  • Also assists the reducer in reaching the silver halide by causing the gelatin to swell and become more permeable
  • Caustic, rubber gloves (nitrile gloves) and apron should be worn
  • Developing solution that splashed onto clothing and walls is corrosive and should be neutralized with fixer (component: acetic acid) or diluted with water
• RESTRAINER, REGULATOR, ANTIFOGGANT/STARTER (BENZOTHIAZOLE)

  • Holds back or restrains the action of the developing agents so they reduce only the silver halide crystals exposed to radiation
  • Potassium bromide (benzothiazole) or potassium iodide
  • Prevents chemical fog or developmental fog
  • The added bromide serves to depress the reduction of the unexposed crystals and acts as an antifog agent, and it restricts the action of the developing agent only to those silver halide cypress that are irradiated
• PRESERVATIVE (SODIUM SULFITE)

  • Antioxidant, protects the hydroquinone from aerial oxidation
  • If hydroquinone is oxidized, there is a decrease in the Dmax and contrast indicators during a sensitometric test, along with a loss of the shoulder on the H & D curve
  • Oxidized developer causes the developer solution to turn from clear, brown liquid to one that is clear and muddy
  • If strongly oxidized, the solution also has the odor of ammonia, because this is a byproduct of the oxidation chemical reaction
  • Most developer replenishment tanks have floating lid inside the tank in addition to tye main lid on the outside to minimize contact with outside
• HARDENER

  • Gluteraldehyde is the most common developer solution hardener
  • Controls the swelling of the gelatin to prevent scractches and abrasions to the emulsion during processing, it maintains uniform film thickness to assust in processing through automatic processor
  • Insufficient hardener will cause films to deposit gelatin on processir rollers, which may cause transport and artifact problems for subsequent films
  • Excessive hardener may cause the emulsion to harden prematurely, preventing chemical interaction with silver halides and trapping moisture in the gelatin
• SEQUESTERING AGENTS

  • The developer may contain metal impurities and soluble salts, such impurities can accelerate oxidation of hydroquinone, rendering the developer unstable
  • Chelates are introduced as sequestering agents to form stable complexes with those metallic ions and salts
  • EDTA (ethylenedianine tetracetic acid) helps forms stable complexes with metallic ions
• FUNGICIDE (ANTIBACTERIAL)


  Added to prevent bacterial growth
• BUFFERS

  • Added to maintain the pH of developer
  • Sodium carbonate
• SOLVENT

  • Chemicals are suspended in water as a solvent
  • The water used for mixing chemistry should be filtered to remove impurities (a 5-10 micron filter is recommended)
  • In tropical climates, it should be treated to eliminate bacteria and fungus that may find the gelatin emulsion an attractive meal
• The developing is the only solution that is dramatically affected by contamination only 0.1% fixer in a developer tank will destroy the ability of the reducing agents (10ml in a 2.5 gallon or 10 L tank)
• The most common cause of contamination is splashing
• IMPORTANCE OF PROPER DEVELOPMENT

  • Development is a chemical reaction governed by time, temperature, and concentration of the developer
  • Long time with low temperature or high temperature with short time will work
  • Any deviation from those parameters will result in a loss of image quality, usually resulting fog
  • Fog cause an increase in base fog and a drop in contrast
  • A fogged image is gray with poor contrast
• 3 WAYS TO FOG FILM

  • Chemical fog
  • Radiation fog
  • Improper storage
• FIXING THE IMAGE

  Once the image is developed it must be treated so it will not fade but remain permanently
• FIXING AGENT

  • Made up of sodium thiosulfate or ammonium thiosulfate and is commonly called hypo
  • The purpose of the fixing agent is to remove or clear all unexposed and undeveloped silver halide crystals from the film emulsion
  • The chemical clears the film so that the black image produced by the developer becomes readily distinguished
• HYPORETENTION

  • The undesired retention of fixer on the emulsion
  • Caused by improper washing of the film
  • Fixers slowly oxidize to form silver sulfide which turns the image yellow-brown
  • Silver sulfide stain is the most common cause of poor archival quality
• SODIUM THIOSULFATE

  • First ingredient in the fixing solution is water which is the solvent used to dissolve the other chemicals
  • The next ingredient is sodium thiosulfate commonly called as hypo
  • Sodium thiosulfate is a salt, most important ingredient in the fixing solution because it dissolves the unexposed silver halide crystals
• HARDENER


  • Used to speed this process causing the emulsion to become rigid
  • Potassium alum, aluminum chloride, or chromium alum
  • The purpose of these hardening agents is to harden and shrink the gelatin in the film emulsion after the accelerator in the developing solution has softened it
  • Hardening of the image is important for proper transport if the image through the processor and to permanently fix the image
  • Used fixer will contain silver making it toxic to aquatic life must be processed as hazardous waste
• DEPLETION OF FIXER HARDENER

  • After a time, the fixer solution will become saturated with silver ions from the emulsion
  • The solution slowly becomes unable to accept additional silver and requires a longer clearing time
  • Automatic processors constantly replenish the fixer solution to eliminate this problem. The silver ions in the fixer can be reclaimed through various silver recovery process