What causes radial fractures to be longer or shorter in glass?
Tempered glass is stronger than normal glass due to rapid heating and cooling. The penetration of window glass by a projectile, whether it is a bullet or a stone, produces cracks which radiate outward (radial fractures) and encircle the hole (concentric fractures).
What is the 3R rule for glass fractures?
What is the 3R rule and how is it applied to the analysis of glass fractures? The 3R rule states that Radial cracks form a Right angle on the Reverse side of the force. This rule enables an examiner to determine readily the side on which a window or pane of glass was broken.
What is the 3 R rule?
The three R’s stands for: Reduce, Reuse and Recycle. This rule is part of the waste hierarchy which is a process used to protect the environment and conserve resources through a priority approach.
What 2 characteristics do high velocity bullets leave in glass?
Higher-velocity bullets will leave a very neat hole. A gun held close to the pane of glass (again, like a human body) will completely shatter it, because the hot gases from the muzzle of the gun escape rapidly and with great pressure. A pane of glass broken with a large stone will look the same.”
What information can glass fractures provide?
Glass fracture examinations can provide information as to the direction of the breaking force and the sequence of multiple impacts. A physical match of two pieces of glass establishes that they came from the same source to the exclusion of all other sources.
How do you tell if glass is broken from inside or outside?
Determine the Direction of Force Find the sharply tapered pieces nearest to the hole (radial break pieces). Be sure you know which is the inside (or outside!) and look at the glass from the side. The force of the bullet hitting one side will break away a crater on the opposite side of the glass.
What type of evidence is glass class or individual?
Associative evidence
What simple property is used to identify glass and match it to glass at a crime scene?
Refractive index
Is Broken Glass Class evidence?
However, glass is usually class evidence therefore the value of evidence will depend on the discrimination powers of techniques used for its comparison. It is class evidence most of the time because without two fitting glass fragments, the glass can be identified but not linked to a specific object.
What are the two most often used methods of glass analysis?
The flotation and immersion methods are best used to determine a glass fragment’s density and refractive index, respectively. The latter involves immersing a glass particle in a liquid medium whose refractive index is verified unit it is equal to that of glass particle.
What are the methods used for the matching of glass evidence?
(g/cm3 (solids); g/mL (liquids)) • One method of matching glass fragments is by a density comparison. Each type of glass has a density that is specific to that glass. If two samples of glass can be differentiated by density, they could not have originated from the same source.
How do you collect and package glass evidence?
Place small glass fragments in paper bindles, then in coin envelopes, pill boxes, or film cans which can be marked and completely sealed. Place large glass fragments in boxes. Separate individual pieces with cotton or tissue to prevent breakage and damaged edges during shipment. Seal and mark the box containing them.
How do you collect evidence from glass?
COLLECTION PROCEDURE: The glass should be placed in a sealed paper bindle or a folded and sealed paper or plastic bag, depending on size. Large pieces of glass with sharp edges should be put into sealed containers (such as cardboard boxes) in which they will not cut their way through.
What is the main ingredient in ordinary glass?
sand
Who tried to destroy fingerprints with corrosive acid?
Comparison is proved by the 14 matching ridge characteristics. Dillinger tried to destroy his fingerprints by applying corrosive acid to them.
Is tempered glass used in crystal stemware?
Tempered glass is used in expensive crystal glassware because it is usually attractive.
What is the main ingredient in glass quizlet?
What is the main ingredient in glass and what is its chemical name? Sand is the main ingredient in glass and is also known as silica or silicon dioxide. it keeps a majority of the glass attached so there are not very many shards. slows down a bullet so it can not penetrate.
Can glass stretch when hit?
When a glass is hit by an object, the impacted surface becomes compressed, whereas the side that is away from the impact stretches due to tension. As a result, the glass breaks and forms fractures.
What type of glass has the highest density?
A layer of “heavy” bromoform is first added to a cylinder. It has a density of 2.889 g/cm3 at 15 °C, so most common glasses will float on its surface….Glass Density Evidence.
| Glass Type | Density/g/cm3 |
|---|---|
| sand | 1.52 |
| fused silica (96%) | 2.18 |
| Corning Vycor® 7907 UV-Blocking Glass | 2.21 |
| Pyrex(R) | 2.23 |
How is glass formed and what is the primary ingredient of glass?
Glass is a hard, amorphous material made by melting sand, lime, also called calcium oxide, and sodium oxide at very high temperatures. The primary ingredient of glass is carbon dioxide. Glass is called an amphibious solid because its atoms are arranged in a random fashion.
What are the two most common ingredients in glass?
Commercial glass or Soda-lime glass: This is the most common commercial glass and less expensive. The composition of soda-lime glass is normally 60-75% silica, 12-18% soda, and 5-12% lime….Types of glass and market application.
| Element | Properties |
|---|---|
| Cerium | To absorb infrared rays |
What are the three main ingredients in glass?
Ingredients for making glass
- Sand or Silica. The main ingredient of glass making is Silica, which as a very high melting point of over 2,000 deg C.
- Sodium Carbonate.
- Lime or Calcium Oxide.
- Other Additives.
- Colour Additives A range of additives can be used to make glass into different colours.
What type of ingredient strengthens the glass?
Boron oxide is one of the main ingredients in so called Pyrex glass. Its ability to strengthen the structure of glass and protect it from thermal expansion, cracking and thermal shock makes it perfect for production of many kitchen cookware, optical component and reagent bottles.
How glass is made step by step?
- Melting and Refining. In order to make clear glass, the right set of raw materials is required.
- Float bath. The molten material from the furnace flows into the float bath which consists of a mirror-like surface made from molten tin.
- Coating for reflective glass.
- Annealing.
- Inspecting.
- Cutting to order.
Why is it called float glass?
It is called “float glass” because of the process by which it was formed; literally floating the liquid glass over liquid tin and slowly cooling it (referred to as annealing) to become what we commonly call “plate glass.”