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rad 254 chapter 12 processing the film latent image

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rad 254 chapter 12 processing the film latent image

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    1. RAD 254 Chapter 12 Processing the Film Latent Image Basics/Dates Universal time and temp: 5 min at 68 degrees F Each MAJOR step is 2X longer than the previous

    3. Development: conversion of latent image to manifest image (black metallic silver) Fixation Removes the UNEXPOSED silver halide crystals Preserves the image

    4. Automatic Processor (90 sec) Items of importance Time for devel and fix = 22 seconds for each Developing agents: Hydroquinone, phenidone/metol/elan Fixing agents: Acetic acid, ammonium thiosulfate

    5. Developing agents Hydroquinone – SLOW acting build up of “blackest blacks” (also known as the reducing agent) Phenidone/metol/elan – act RAPIDLY to build up GRAYS Buffering agents (to maintain alkalinity) – sodium carbonate/sodium hydroxide (Lye) Restrainers – “Potass”ium bromide/iodide – prevents developer from converting the UNEXPOSED silver halide to black metallic silver

    6. Devel. Cont. Preservative – sodium sulfite Hardener – Gluteraldehyde (others used: potassium alum, aluminum chloride, chromium alum

    7. Fixing Agents Same hardener and preservatives as devel. Acetic acid – activator – stops action of developer Ammonium thiosulfate – FIXING AGENT Acetate – “Buffering agent” – helps maintain proper pH

    8. Washing Universal solvent = Water “Hypo retention” residual chemicals on the film = turning the film brown over time MUST BE CHECKED FOR MAMMO

    9. Automatic Processing Six total systems Transport Temperature Circulation Replenishment Dryer Electrical

    10. Transport Rollers and transport “racks”, drive gears TRANSPORT ROLLERS are 1” in diameter (3.14” circum.) “Pi lines” are a common artifact “Guide shoes” also can cause artifacts (especially with new processors and racks) Cross over rollers Time guidelines +-2 percent of required time

    11. 5 “other” systems Temperature – proper temps. For developer, wash and dryer Circulation – agitates chemicals, FILTERS DEVELOPER Replenishment – meters and replaces chemistry Dryer – Dries film (know diff. between wet and “tacky” Electrical – All electrical areas

    12. Special Processing Daylight – Enables one to place a cassette in the daylight processor and the processor opens/processes/reloads cassette Dry Processing: Photothermic – Used laser to form a latent image and HEAT to make it visible Thermographic – Uses heat to DIRECTLY produce the image

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