HAIR, FIBERS,

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HAIR, FIBERS, PAINT

• PART 3 - PAINT

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I. INTRODUCTION TO PAINT

• Our environment is literally surrounded with
  millions of objects whose surfaces are painted.

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I. INTRODUCTION TO PAINT

• A. Paint is one of the most prevalent types of
  physical evidence.
• 1. Hit and run cases
• 2. Burglary cases

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I. INTRODUCTION TO PAINT

• B. It is often necessary to compare two or more
  paints to establish common origin.
• 1. May be possible to associate a car to the
  crime scene
• 2. Can also identify the color, make, and model
  of a car

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II. COMPOSITION OF PAINT

• A. Paint consists of pigments suspended in a
  binder
• 1. Pigments impart color
• a. usually mixtures of different inorganic
  organic compounds
• b. Produce specific colors and properties

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II. COMPOSITION OF PAINT

• A. Paint consists of pigments suspended in a
  binder
• 2. Binder provides the support medium for the
  pigments
• a. Usually is a polymeric substance

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II. COMPOSITION OF PAINT

• A. Paint consists of pigments suspended in a
  binder
• 3. Paint is composed of a binder and pigments,
  all dissolved in a suitable solvent
• 4. After the paint has been applied to a
  surface, the solvent evaporates, leaving behind a
  hard polymeric binder and any pigments that were
  suspended in it.

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III. AUTOMOBILE PAINT

• A. Electrocoat Primer
• 1. First layer
• 2. Consists of epoxy-coat resins
• 3. Is electroplated on to the steel
• 4. Provides corrosion resistance
• 5. Ranges in color from black to gray

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III. AUTOMOBILE PAINT

• B. Primer Surfacer
• 1. Epoxy-modified polyesters or urethanes
• 2. Smoothes out surface hides seams
• 3. Highly pigmented - to minimize color
  contrast between primer and topcoats

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III. AUTOMOBILE PAINT

• C. Basecoat
• 1. Provides the color
• 2. Resists the elements of weather, UV
  radiation, acid rain
• 3. Acrylic base polymer

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III. AUTOMOBILE PAINT

• D. Clearcoat
• 1. Unpigmented
• 2. Improves gloss, durability appearance
• 3. Acrylic based polymer or polyurethane
  clearcoats

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IV. TYPES OF PAINT

• A. Latex
• B. Acrylic
• C. Enamel
• D. Lacquer

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V. COMPARISON OF PAINT

• A. Color
• B. Surface
• C. Texture
• D. Color-layer sequence

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VI. TESTS OF PAINT

• A. Microscope(color, texture, layers, surface)
• B. Pyrolysis gas Chromatography (binder)
• C. Infrared Spectrophotometry (binder)
• D. Emission Spectroscopy(pigments)
• E. Neutron Activation Analysis (pigments)
• F. X-ray diffraction (pigments)
• G. X-ray spectroscopy (pigments)

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VI. COLLECTION OF PAINT EVIDENCE

• A. Paint chips are picked up with tweezers or
  scooped with paper.
• B. Druggists folds or glass or plastic vials.
• C. Paint on objects --package the whole item
  carefully.
• D. Standard reference samples
• 1. To bare metal
• 2. 1/4 inch square
• E. Tools - packaged for examination