What is glitter?
How is it made?
- synthetic multi layered particles
- plastic (polyethylene terephthalate/ PBT (polybutylene)/ PMMA) or aluminium, or a hybrid
- glitter particles can either be layers of those plastics or layers interspersed with aluminium or just aluminium
- they are cut from rolled sheets
- shape tends to be hexagonal, square or rectangular - cost saving exercise so none left on sheet at end
- can be custom shaped - but less cost effective
Where is glitter found?
- can be found in decorative cosmetrics, sunscreens, and various personal care products (moisturisers, body washes, handwashes, toothpastes)
- gel pens, temp tattoos, glues, paints, toy slime, decorative drinking glasses, loose (no vehicle)
- glitter can be on clothes stuck on to it - glitter can also be encrusted into garments or woven into fabrics, threads, strands, and yarns
What is the difference between glitter and shimmer (synthetic, plastic content, variation)
- glitter is fully synthetic
- mica-based shimmer is natural (borosilicate glass not so natural)
- whether mica is used alone or coated with metal oxides it never contains plastic
- glitter almost always contains plastic (unless purely aluminium)
- glitter of a given type will have identically shaped and sized particles and have no variation (same thickness as all cut from same machines at same time)
- shimmer is naturally occurring mineral so shimmer particles are irregularly and randomly shaped and size - they also have varying layers as well
What are the recovery considerations for glitter? (what should it be analysed as, how to find it, what to lift it with, what is best to store, embedded particles, storage conditions)
- glitter (and shimmer) should be analysed as multi-layered paint flakes
- use a high intensity light source for recovery of glitter (it is designed to catch the light so the higher the intensity, the more likely to pick those particles up)
- must not be lifted with J-Lar or acetate - as it is multi-layered they are prone to being damaged and layers being pulled apart of delaminated
- use post-it notes
- can then be folded on top of self and wrote on
- glass or plastic vial is the best option to ensure not bent or snapped then bag
- embedded particles must not be removed at scene unless absolutely necessary
- do not refrigerate or freeze as water may delaminate layers
What is the analytical workflow of glitter?
1 - gross examination, recovery, and collection
2 - preliminary evaluation of physical characteristics
- use micrometer gauge or microscopically to measure thickness (will be in order of microns)
(physical fit assessment
- glitter particles are so small, unlikely that a single particle is going to be broken apart or cut in such a way to get physical fit like you would a paint flake.
- do get manufacturing defects – can almost be as probative as physical fit)
3 - all microscopic techniques
- best modes for glitter – reflectance and transmission modes
- recommend x700 for particle morphology – lumps and bumps on surface, some have ridges cut in to enhance glitter
4 - microspectrophotometry
- more important for glitter particles than other forms of trace evidence as colours are optically variable (colours will change depend where looking)
5 - infrared spectroscopy
- ATR-FTIR is best form for glitter
- will give us plastic chemistry – PMMA, PBT, acrylic, polyester based etc.
- limited success using micro FTIR and standard one (two potassium bromide discs)
6 - measure specific gravity
- put a glitter particle (solid) into two liquids of varying densities and noting when it neither floats or sinks and sits between layers – gives us specific gravity measurements
- check colour fast first – a lot of liquids acts as solvent and if strip of colour or glitter particle before analysing colour – not good
7 - raman (micro) spectroscopy
- good for looking at tiny particles
- can look at polymer layers as raman is very good at looking at plastics
8 - SEM-EDX
- will show you microstructure detail and elemental composition of layers (aluminium)
- can’t get this with raman as aluminium can’t be picked up with raman
What are four things to note when analysing glitter?
- number of particles and their physical dimensions
- location of particles – context (location of something on garment (substrate) is very important as you crime reconstruction – gives context)
- number, sequence, thickness, and colour of layers (beware colour subjectivity)
- manufacturing defects, weathering, delamination, corrosion, damage…
- manufacturing defects are highly discriminative – can provide really high probative value
- can match it back to actual machine and therefore manufacturer
What three things should be done when analysing glitter?
- oblique or alternate lighting as particles reflect differently (lighting can have big impact on what you see)
- alternate between black, grey, and white backgrounds to facilitate colour determinations
- Q vs. K comparisons must be performed side-by-side using the same background colour
What is a useful for technique to analyse glitter due to its plastic content?
- ATR-FTIR for plastic chemistry
- almost all glitter particles are plastic based
What is important when analysing glitter particles?
- must look at both sides as unlike shimmer particles, glitter particles do not have the same layer on both sides
Are there any forensic glitter databases?
- no
- would be much easier to create and maintain rather than cosmetics database (no mixing considerations as glitter isn’t designed to interact with skin or to be used in layers, it also won’t degrade as is made of plastic)
- glitter database would also have more value than cosmetics one
What can be said about the research on glitter in forensic science?
- very limited research on background, transfer, persistence and activity level
What must be considered when recovering glitter? (substrate considerations, multiple associations, nature of contact, two-way transfer, retention time)
- substrate considerations (absence of glitter doesn’t mean glitter was absent)
- glitter is shiny and sticks really well but if shiny surface might not stick as well
- multiple associations mitigate coincidental transfer
- nature of contact/forces involved
- two way transfer can occur
- must be aware of high retention (background levels must be considered when looking at interpretation and context)
- can find glitter particles in carpet from years ago as they persist well due to small size and light weight
Along with other types of traces, what can be said about glitter analysis?
- expensive
- time consuming
- requires skill
Why is raman really useful in analysis of glitter?
- will show differences in spectral peak intensities
- can differentiate between two slightly different plastics and therefore two different glitter particles
- even better if put two spectra through chemometrics package and run PCA will show differences in spectra
- in court, got numbers to prove it
What are seven properties that Bob Blackledge suggests as being properties that give you an ideal piece of trace evidence?
1 - highly individualistic, e.g. size, shape, thickness, specific gravity, morphology, number and thickness of layers, chemistry of layers, colour, special effects, manufacturer and/or geographical origin, cutting defects, vehicle, etc.
2 - nearly invisible (until it catches the light)
3 - high probability of transfer and retention
4 - quickly collected, separated, and concentrated (easy to do as it is a solid particle, and it is made of plastic, so it is hardy)
5 - easily characterised (only a single particle required to run IR and raman spectra)
6 - databasing capability and MVA
- because of all parameters and measurements we take in analytical workflow of a glitter particle are easily data based, can create data bases of glitter particles
- not as effected as cosmetic residues as they are plastic and don’t tend to mix with matrix they are within
7 - relatively persistent and resistant to degradation (not affected by UV radiation or degraded by all the things makeup is degraded by in the environment)
How can SEM be used to differentiate between glitter particles?
- pair of SEM images show that these are incidentally 2 particles from same glitter pot – same shape, size, and colour
- but there is a difference in cross section in SEM. backscatter image shows elemental density and one has brighter central strip (higher density of aluminium
- when scientists peeled these layers apart from this glitter particle, noticed two layers of aluminium instead of one
- wouldn’t have picked up from SEM images, that there was a single layer of aluminium in one and double layer in other
Why is glitter a problem?
- plastic is a big problem
- microbeads such as those used in exfoliating products such as facial scrubs, body scrubs etc. are banned
- these persist on waste water and kill marine creatures (they eat them and guts get filled up with them)
- EU are now banning glitter (plastic)
- but the average human consumes around 2000 microplastics per week (some will be retained in body (blood stream, lung tissue from inhalation and in brain tissue))
- plan to get rid of all glitter by 2031
What are some glitter alternatives?
- glitter and shimmer can produce more or less the same effect and shimmer isn’t same as glitter and does not contain plastic
- eucalyptus tree derived cellulose - Lyocell (rayon)
- BioGlitz, Glitterevolution, Submission (biodegradable non glitter plastic)
- glass based glitter particles
If plastic glitter is banned what does this mean for trace evidence?
- just because it is banned, doesn’t stop someone having it in their cupboard, doesn’t stop a child using it, doesn’t stop criminal from picking it up from crime scene
- just because can’t buy it, people will still have it
- because it persists a lot – even more chance of it being transferred and encountered as trace evidence
