Glitter

Question 1

What is glitter?

Answer 1

• Not the same as shimmer
• Synthetic multilayered particles - plastic or aluminium, or a hybrid
• Cut from rolled sheets, tend to be hexagonal, square or rectangle, or a custom shape

Question 2

Where can glitter be found?

Answer 2

• Decorative cosmetics
• Sunscreens
• Gel pens
• Temporary tattoos
• Glue
• Paints
• Woven in fabric

Question 3

What is shimmer?

Answer 3

• Mainly mica based
• Used on its own (pearlescent effects)
• Used as a substrate then coated with various metal oxides

Question 4

How are interference pigments made?

Answer 4

• Middle layer of mica (low refractive index)
• Surrounded by metal oxide layer that has a high rerfractive index
• Can be multilayered to give more discriminatory value
• Thickness of metal oxide layers dictate colours reflected and transmitted

Question 5

What are some alternative substrates to mica in interference pigments?

Answer 5

• Borosilicate glass, silica, alumina
• Thinner and more uniform than natural mica
• Colourless (mica is slightly yellow)
• Lower RI than mica - increases interference

Question 6

Glitter vs shimmer

Answer 6

• Glitter is synthetic, mica based shimmer is natural
• Mica alone or coated with metal oxides never contains plastic, glitter almost always does (or is aluminium based)
• Glitter will have identically shaped and sized particles, shimmer particles are irregular and randomly shaped and sized

Question 7

What are some recovery considerations for glitter and shimmer?

Answer 7

• Should be analysed as multilayered paint flakes
• Use a high intensity light source
• Must not be lifted with J-Lar or acetate
• Glass or plastic vial is best then a bag
• Embedded particles must not be removed at scene
• Dont refrigerate or freeze

Question 8

What is the analytical workflow for glitter?

Answer 8

1. gross examination, recovery, collection
2. preliminary evaluation of physical characteristics (microscopy of gauge)
3. physical fit - manufacturing defects
4. all microscopic techniques
5. microspectrophotometry
6. ATR infrared spectroscopy (plastic chemsitry)
7. specific gravity
8. raman micro spectroscopy (polymer layers)
9. SEM-EDX - elemental composition of layers

Question 9

What should you look for with glitter evidence?

Answer 9

• Number of particles and their physical dimensions
• Location of particles
• Number, sequence, thickness and colour of layers
• Manufacturing defects, weathering, delamination, corrosion, damage

Question 10

What can manufacturing defects tell you?

Answer 10

• Probative value
• Has the potential to match to a particular machine and so the manufactuer

Question 11

What different analysis methods should be used when analysing glitter with microscope?

Answer 11

• Oblique or alternate lighting as particles reflect differently
• Alternate between black, grey, and white backgrounds to facilitate colour determinations

Question 12

What are benefits of glitter as trace evidence?

Answer 12

• highly individualistic - different shape, thickness, size, number, morphology
• nearly invisible
• high probability of transfer and retention
• quickly collected, separated and concentrated
• easily characterised
• databsing capabilities
• relatively persistent and resistant to degradation