1. Glass Analysis
M. Phillips

2. Composition Silicon dioxide mixed with various metal oxides Hard
Brittle
Amorphous solid
When sand is mixed with other metal oxides, heated to a high temperature, and then cooled to a temperature without crystallization, glass is produced. Amorphous solid – no crystals.

3. Standard Glass Soda lime glass Bottles Picture frames Window panes
Na2CO3 + sand + CaO (quicklime)
Bottles
Picture frames
Window panes
Breaks into sharp shards when it falls.

4. Tempered Glass 4-5x stronger than standard glass
Made by extreme heating and rapid cooling
Shatters into small oval pebbles (“safety glass”)
Coffee makers, oven windows, computer and phone screens, car headlights, Pyrex

5. Laminated Glass
Sandwiches a sheet of plastic between two panels of glass
When the glass breaks, it sticks to the plastic film
Cracks only at point of impact
Windshields in cars

6. Acrylic/Plexiglass Thermoplastic 20x stronger than glass
½ weight of glass
Flammable
Dents on impact rather than cracking or shattering
Aquariums, helmets, airplane windows

8. Radial Fracture Cracks in glass extending outward
Similar to spokes of a wheel at point of impact
Can feel the ridge on the REVERSE side of impact
FIRST fracture type formed

9. Concentric Fracture
Cracks in glass forming a rough circle around point of impact
Can feel the ride on the SAME side as impact
Forms SECOND
Require more force than radial

10. Crack Formation

11. Direct Impact From an object being used to smash the glass while held
Solid center

12. Projectile Impact From an object being thrown at the glass
Crater/hollow center

13. Direction of Travel Exit hole is larger than entrance hole
Can be used along with feeling fracture
lines to determine side/angle of impact

14. Sequence of Fractures
A radial fracture ALWAYS terminates at an existing line of fracture.
This allows us to tell what sequence they occurred in.

15. Impact radial fracture lines end abruptly at those produced by a previous impact. In this case, fracture B followed fracture A.

16. Density

17. Refractive Index Physical property
Ratio of speed of light in a vacuum to the speed of light through a medium
Different liquids have a different RI
If a glass sample has the same RI as the liquid, it will not be visible
If the glass sample has a different RI, there will be a Becke line – a dark edge or boundary

18. Becke Line