forensic analysis of fibres

Question 1

elemental analysis for glass- 1980s

Answer 1

 Initially, classifying specimens as to source to rule out or confirm alibis.
 manufacturers improved quality control so refractive index was not as discriminating - greater discrimination power was needed
 most elemental analysis of glass is destructive (apart from X-Ray Fluorescence, XRF)
 Physical and optical comparisons are well established and widely accepted in courts internationally
 Tests are non-destructive
 Tests use inexpensive instruments
Elemental analysis is done after all non-destructive tests and only when additional discrimination is needed

Question 2

Differences in RI are due to major elements in glass:

Answer 2

Si ~30% Na~ 8% Ca~ 8% Mg ~ 2% K ~ 1.5%

Question 3

Glasses may have same RI but differ in minor elements:

Answer 3

Al ~ 1% Fe ~ 0.3%

Question 4

Or differ in trace elements:

Answer 4

Ba Mn Ti Sr Zr ~ 0.1%

Question 5

classification and discrimination of glass

Answer 5

Classification of glass - major elements
Discrimination of glass - minor or trace elements