4-3 Forensic Analysis of glass Unit 4: Properties of Matter and the Analysis of Glass

Comparing Glass Fragments To compare glass fragments, a forensic scientist evaluates two important physical properties: refractive index Density

refractive index The immersion method is used to determine a glass fragment’s refractive index.

immersion method It involved immersing a glass particle in a liquid medium whose refractive index is adjusted be varying its temperature.

refractive index At the refractive index match point the contrast between the glass and liquid is at a minimum.

Density The floatation method is used to determine a glass fragment’s density.

Flotation Method It involves immersing a glass particle in a liquid whose density is carefully adjusted be adding small amounts of an appropriate liquid until the glass chip remains suspended in a liquid medium.

Glass fracture patterns By analyzing the radial and concentric fracture patterns in glass, the forensic scientist can determine the direction of impact by applying the 3R rule.

Radial fracture patterns

3-R Rule Radial cracks for a Right angle on the Reverse side of the force.