Footwear Impressions Flashcards
Describe compression molding?
- open mold process, usually 2 pieces
- possible left and right molds made by different makers
- Ethylene Vinyl Acetate often used
- flash is the excess material from the sides of mold
- can be made with 2 or more colours
- flashing could be where colours meet
- pre-measured biscuits placed in mold
- die cut to fit shoe, causing variations
Describle Injection Molding.
Injection molded unit soles are made separately and glued or sewn.
Direct Attach injection outsoles - mold opens and closes around upper portion of shoe. Flash usually left where mold comes together (toe and heel). Sprue is mark left on shoes from where soling material was injected.
Describe Calendering.
- raw un-vulcanized rubber compounded put through rollers to make flat and a given thickness.
- fed into calender machine design rollers.
- die cut to size.
- flaws or damage to roller will likely show up
- stretching of material while its handled can change appearance
- random characteristics are often added during handling and cutting.
Describe Die Cutting.
- aka Wellman out sole cutting
- steel die placed on rubber and machine stamps the outsole.
- differences around the edge, the placement of the die within the design
- edges will be straight with vertical striations from the die
- may be ground off or covered with a foxing material.
Footwear Impression:
What are the Scientific Principles?
- All object in the universe are unique.
- The principle of identification.
Describe the Principle of Uniqueness.
No two things…
that happen by chance ever happen in the exactly same way
are ever constructed or manufactured in exactly the same way
ever wear in exactly the same way
ever break in the same way
Describe the Principle of Identification.
If proper scientific methodology is followed and there exists sufficient clarity in an impression, it may be identified as orginated from a particular source.
Features of Accidental Characteristics of footwear wear.
wear = erosion of outsole from friction and abrasion between the shoe and the surface it comes in contact.
affected by foot type, weight, occupation, functions, habits, materials, surface
value of wear increases more shoe is worn
identification should not be based on wear alone
minor disagreements should not preclude an identification.
What are accidental characteristics that can be used to identify footwear?
cuts
tears
goughes
nicks
specific wear marks
randomly placed nails
rocks/imbedded objects
What are the 4 aspects to consider for accidental characteristics of footwear?
- size
- shape
- position
- orientation
What is considered when evaluating accidental characteristics?
Clarity
Degree of Uniqueness
Reproducibility of characteristics
Confirmation of them as random characteristics
What is the Philosophy of Footwear Identification?
Footwear Identification is estabished by the agreement of class and accidental characteristics of such significance or number that no other logical conclusion can be reached
Factors to consider when arriving at an opinion regarding footwear comparisons.
The examiner’s experience
The impression’s clarity
The uniqueness of the characteristics
What are the opinions that can be reached for Footwear and Tire Identifications?
Exclusion - the known footwear or tire was not the source of the impression
Identification - known footwear or tire was the source of the impression
Association of class characteristics - known is a possible source. Includes sources with the same class characteristics.
Higher degree of Association - characteristics observed exhibit strong association, quality or quantity insufficient for identification.
Inconclusive - evidence lacked detail for a meaningful conclusion to be reached.
What are Schallamack Abrasions?
caused by rubber being scuffed and lifting from the surface then falling back
usually seen on rubber
change quick, can identify small area
do not eliminate if pattern different
Random tearing of elements of the outsoe that results in identifiable, tough relatively transitory accidental characteristics.
