Glass Examination Flashcards
glass characteristics
hard brittle, transparent
what is doping in glass
adding other chemicals into the glass
whta is glas made of
silicon oxide
how is glass made
melting sand and allowing it to cool and crystalize
what are some common dopants
sodium carbonate, calcium oxide, boron oxides
how is tempered glass made
heated and rapidly cools to break into not sharp pieces
what is laminated glass
where PVB is sandwiched between 2 pieces of glass
what is a fracture match
the only way to individualize a fracture where a piece is perfectly fitted into a crack
what are some tests for class evidence
density, IR, color, thickness, flatness, surface features
how do you collect glass peices
collection using forceps
how do you collect hair/fibers
by foreceps
what are some surface features of glass
patterned glass (frosted), coated glass (reflective/UV protection), float glass (really flat glass)
how is RI measured
glass in oil, increase temp and when disappeared then that is RI (Becke line)
how float glass made
melted glass over molten tin (gives one side fluorescence)
how do you test density
float/sink methiod
What is GRIM
a measurement of glass IR on hot plate with microscope
where is the crater shape found
in side of non-impact
how does the glass break
opposite side bends then breaks to produce radial cracks
then impact side breaks making concentric cracks
what side are walners cracks on for radial cracks
on the opposite side of impact
what are t-junction
where one crack will stop another
the one that appears first will be the top of the T
what is different about thermal cracks
they have no walner cracks, so can’t tell directionality
what are some things you have to find about glass
of strikes, glass fragment size, distance between glass and shooter
