FORS-2107EL Lecture Notes - Lecture 14: Microtome, Wave Power, Conchoidal Fracture
27 Jun 2018
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Forensic Science - Day 14 2018.03.12
Paint Analysis
Nature of Paint Evidence
-Paints are typically used as coatings on a surface, for aesthetic and/or protective
purposes, and may be used to increase UV or moisture resistance
-Paints usually consist of three classic components:
-Solvent (organic or aqueous)
-Colourant (pigment)
-Binding Agent (polymer)
Definitions
-Architectural Paint: coating encountered around a typical household
-Dye: a colouring agent that is soluble in the medium in which it is dispersed
-Enamel: A pigmented coating that has a high gloss (luminousity) when it dries
-Lacquer: Clear or pigmented coatings that dry quickly through evaporation of the
solvent
-Latex: A suspension of a pigment in a water based emulsion of a resin
-Paint: A suspension of a pigment in a liquid vehicle, or any surface coating designed
for protection and/or decoration of a surface
-Pigment: A fine powder that is insoluble in the medium in which it is dispersed
-Stain: a solution of dye or a suspension of a pigment designed to colour, but not
protect, a wood surface
-Varnish: A clear solution of oils and organic or synthetic resins in an organic solvent
Collection and Preservation of Paint Evidence
-Questioned samples (Q) are those that will be compared against samples from a
known (K) source to determine whether or not they share a common origin
-Q samples should inclose all lose and transferred garments
-K samples are derived from a source under investigation
-Ex. from car in alleged hit and runs (where Q samples are taken from the victim) or
from painted window frames in break and enter cases (where Q samples are taken
from a crow bar or from suspect)
-When paint evidence is found, it is very important to manually recover all fragments,
prior to tape lifting of other trace evidence, since tape can complicate handling and
may contaminate chemical features of the fragments by altering the apparent
chemical make up of the fragment
-Collection is usually done with tweezers or by shaking the object
-K samples should be collected from multiple sites as close to, but not within, the
areas of damage, or even those suspected as the site of transfer, because the
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Document Summary
Paints are typically used as coatings on a surface, for aesthetic and/or protective purposes, and may be used to increase uv or moisture resistance. Paints usually consist of three classic components: Architectural paint: coating encountered around a typical household. Dye: a colouring agent that is soluble in the medium in which it is dispersed. Enamel: a pigmented coating that has a high gloss (luminousity) when it dries. Lacquer: clear or pigmented coatings that dry quickly through evaporation of the solvent. Latex: a suspension of a pigment in a water based emulsion of a resin. Paint: a suspension of a pigment in a liquid vehicle, or any surface coating designed for protection and/or decoration of a surface. Pigment: a ne powder that is insoluble in the medium in which it is dispersed. Stain: a solution of dye or a suspension of a pigment designed to colour, but not protect, a wood surface.
