1. Glass Investigation

2. There are several types of Glass That might be found in a Crime Scene 1.Plexiglas (Actually plastic) 2.Window Glass 3.Mirror 4.Incandescent light bulb 5.Florescent light bulbs 6.Tempered glass

3. Plexiglass Characteristics: Flexible (bends) Not Brittle, does not shatter Can be many colors Low density Example Uses: Used in picture frames Basement windows Sculpture Hobby and toy pieces

4. Window Glass Uses Picture frames Windows Characteristics Not highly Colored Very reflective of light Brittle, shatters Medium density

5. Mirror Characteristics Similar to window glass Brittle, shatters easily Color coated 1 side only Fractures along sharp edges Very reflective of light Medium density

6. Light Bulbs Incandescent Bulb Low density Thin Clear or opaque color in the glass Florescent Bulb Tube shaped Thin Color Coated on inside not in the glass Never clear

7. Tempered Glass Characteristics High Density Does not fracture or form sharp edges Strong Shatters into small pieces

8. Analyzing the Glass Common examinations made with glass include: DensityDensity: To Test density, the usual method of determining mass, then volume by water displacement is used to calculate density D= m/v ColorColor: Samples are visually examined and their color is compared to samples found at the crime scene. Fracture shape: Suspect pieces are examined for their shape, to determine if their fracture lines match fracture lines on Crime scene specimens.

9. Glass Density A Measure Mass 1.Obtain a sample of several pieces (shards) that will all fit into a 50 ml graduated cylinder (USE TWEESERS to handle glass) 2.Using a piece of tare paper, measure mass on triple beam balance 3.Write down mass of glass B Measure volume 1.Measure out exactly 30 ml water (watch exactly where meniscus is) 2.Tilt cylinder to the side and gently slide in all the glass pieces 3.Measure the amount of volume difference and 4.Write down volume of glass. 5.Calculate: Density = mass ÷ volume C Repeat 2 all measurements more times using different pieces of the same type of glass and average the densities. Repeat procedures A, B+C for all types of glass.

10. Glass Color Observe the glass shards and determine the color of the pieces, carefully distinguish if there is only 1 sample of glass or more than 1. Note in your journal the color name as listed at RGB color mapping site: http://web.njit.edu/~kevin/rgb.txt.html http://web.njit.edu/~kevin/rgb.txt.html Compare the color to broken glass at the crime scene to determine of there is a match. Be sure to not in your journal positive or negative match.