Lesson 3 Flashcards
Holds silver halide crystals uniformly in place, preventing clumping and ensuring consistent image quality.
Mechanical Support
Its porous nature allows developer and fixer solutions to penetrate and interact with the silver halide crystals during processing.
Chemical Permeability
Being transparent, gelatin permits light to pass through without distortion, essential for accurate image reproduction.
Optical Clarity
Enables the film to withstand bending and handling without compromising the emulsion’s integrity.
Flexibility
The properties of silver halide crystals are fundamental to the film’s performance:
Size and Shape
Chemical Composition
Electrical Properties
Sensitivity Specks
Typically around 1 micrometer (µm) in size, these crystals can be tabular (flat and triangular), cubic, octahedral, or polyhedral. The shape and size influence the film’s sensitivity and resolution.
Size and Shape
Modern radiographic films predominantly use silver bromide, constituting about 95-98% of the crystal composition, with silver iodide making up the remaining 2-5%.
Chemical Composition
Crystals possess a negatively charged surface due to the presence of halide ions (Bromide and Iodide), while the interior is positively charged (Silver).
Electrical Properties
Intentional imperfections, often introduced using silver sulfide, act as sites where latent image formation begins by attracting free silver ions during exposure.
Sensitivity Specks
are pivotal in capturing high-quality radiographic images.
Emulsion Layers
also known as the substratum or subbing layer
Adhesive Layer
is a vital component of radiographic film, situated between the emulsion and the base.
Adhesive layer
The adhesive layer maintains a firm bond between the emulsion and the base, ensuring they remain in proper contact during handling and processing. This bond is crucial for preserving the film’s structural integrity and preventing issues such as separation or peeling of the emulsion from the base.
Ensuring Proper Contact and Integrity
By securely attaching the emulsion to the base, the adhesive layer helps prevent the formation of bubbles or other distortions that could occur when the film is bent during handling or processing. This stability is particularly important when the film is wet and subjected to the heat of development processes.
Preventing Distortions
is indispensable for maintaining the cohesion and functionality of radiographic film, ensuring that the emulsion and base work together seamlessly to produce clear and accurate images.
Adhesive Layer
film serves as its foundational support, providing a stable structure onto which the emulsion layer is coated.
Base
Historical Evolution of Film Base Materials:
Glass Plates
Cellulose Nitrate
Cellulose Triacetate
Polyester
In the early days of radiography, were used as the base material. While they offered excellent dimensional stability, their fragility and weight posed significant challenges.
Glass Plates
Introduced: in the 1920s, replaced glass plates. Despite being lighter and more flexible, it was highly flammable, leading to safety concerns.
Cellulose Nitrate
In the mid-1920s, emerged as a safer alternative to cellulose nitrate. It retained flexibility and was less flammable but lacked optimal dimensional stability.
Cellulose Triacetate
Since the 1960s, it has been the preferred material for radiographic film bases. It offers superior strength, flexibility, and dimensional stability, ensuring consistent image quality and ease of handling.
Polyester
Key Characteristics of the Polyester Film Base:
Thickness
Dimensional Stability
Transparency and Tint
Coating
Typically ranges from 150 to 300 micrometers (µm), providing a balance between durability and flexibility.
Thickness
Maintains consistent size and shape during exposure to processing chemicals and varying temperatures, preventing image distortion.
Dimensional Stability
