Unit 6: Glass

Borosilicate glass

Glass to which 5% borax is added to resist breaking when heated or cooled.

Colored glass

Glass that is altered in color by the addition of metal oxides or colloidal iron and sulfur.

Lead glass

Glass that contains lead (Pb) to increase its refractive index and density, used for creating ‘crystal’.

Float glass process

A method of making flat glass by floating molten glass on a pool of tin while cooling.

Laminated glass

Glass used in windshields, consisting of two sheets of glass with plastic between them.

Tempered glass

Glass that is strengthened by rapid heating and cooling, used in car side windows.

Radial cracks

Straight lines that extend from the point of impact on glass, forming first.

Concentric cracks

Circular lines of broken glass that appear around the point of impact from continued pressure.

Entry side of glass

The side with a smaller hole and smooth surface where the force was applied.

Exit side of glass

The side with a wider hole and crater shape indicating the point where glass broke outward.

3R Rule

Radial cracks give rib marks, which can help determine the side of impact.

Glass transfer evidence

Minute glass particles that scatter backward from all parts of an object after impact.

Collection of glass samples

Glass fragments should be packaged carefully to avoid further breakage.

Optical properties of glass

Characteristics such as color and refractive index used in comparing glass samples.

Non-optical properties of glass

Surface wear, striations from manufacturing, thickness, and surface film or dirt.

Becke line

A bright halo observed near a particle immersed in a liquid of a different refractive index.

Refractive index

The ratio of the velocity of light in a vacuum to the velocity of light in another medium.

Fluorescence

A method to analyze glass by observing how it emits light under certain conditions.

Scanning electron microscopy

An analytical technique that provides detailed images of glass at a microscopic level.

Atomic absorption spectroscopy

A technique for analyzing glass composition by measuring the absorption of light.