Questioned document analysis-Richard

Question 1

Name 5 techniques for QDA?

Answer 1

VSC
CIE LAB colour analysis
raman spectroscopy
TLC
ESDA

Question 2

Ballpoint pen

Answer 2

rotating steel ball tip
paste ink composition
characteristic striations
gooping of ink
furrowed

Question 3

Fibre tip pen

Answer 3

fibrous tip with ink reservoir
very solid deposition
near brush like stroke
less furrowing or unfurrowed

Question 4

roller ball pen

Answer 4

similar to ballpoint
more fluid ink type
greater ink saturation
pigment based
no striations or glooping
furrowed

Question 5

4 non destructive techniques for ink comparison

Answer 5

microscpoic examination of text
video spectral comparison
CIE Lab colour analysis
raman spectroscopy

Question 6

3 destructive techniques for ink comparison

Answer 6

TLD
HPLS/CE
FTIR of ink

Question 7

video spectral comparison

Answer 7

a white item such as piece of paper is white because reflects equally

a black item is black because absorbs equally
that doesn’t mean it responds in the same way to wavelengths outside of this region
-infrared
-UV

Question 8

Raman spectroscopy

Answer 8

drugs, explosies, firearms chemistry

can be used to differentiate ink types

non destructive

Question 9

What is raman SERRS?

Answer 9

surface enhances - possible localised damage

• requires the addition of colloid reagents
• a means of increasing sensitivity

Question 10

how does raman spectroscopy work?

Answer 10

uses a mono-chrome laser or high intensity light source to illuminate sample

light interacts with sample in variety of ways

• reflection
• absorption
• scattering
• fluorescence

scattered light which has interacted with the chemical structures within out sample can provide insight into the composition of the sample

the spectroscopist is interested only in a portion of the scattered radiation

• raman/stokes radiation -photons
• a different wavelength to the original light source
• gives info of chemical and molecular structure

Question 11

Lab* colour

Answer 11

method of determination of colour coordinates

• dye
• paint
• food

human eye too insensitive for eyeball analysis

• variations in colour appreciation
• male colour gamut generally lower than female

colour often defined by:

• red/green/blue
• hue/saturation/luminance
• cyan/magenta/yellow/key

device dependent

• each pixel has to be translated into the colourspace of whatever we are viewing out image on
• conversion losses-gamut
• gamma correction

Question 12

CIELab*

Answer 12

device dependent

used as basis for colour conversion

L=lightness
A=red/green
B=blue/yellow

lightness is independent of colour

Question 13

Thin layer Chromatography

Answer 13

separates ink into its consistent components

small sample of ink is removed from the document using a micro-punch

then dissolved in appropriate solvent e.g methanol

can be further concentrated

Question 14

TLC -Preparation

Answer 14

samples loaded onto TLC plate

• normally silica
• various mesh sizes
• loaded using glass capillary

placed in a saturated solvent tank

Question 15

TLC - Separation

Answer 15

solvent travels up plate by capillary action

separation is driven by the differential solubility of components in:

• the mobile phase - solvent
• the stationary phase - silica
• polar compounds tend to have a stronger interaction with the silica stationary phase

separation produces a characteristic pattern of bands

• can be used comparatively
• R.F value allow lab/lab comparison or qualitative analysis

Question 16

advantages of TLC

Answer 16

simple
rapid
effective
cheap

Question 17

disadvantages of TLC

Answer 17

chemical development
visualisation
may not differentiate between similar inks

Question 18

what does HPLC stand for?

Answer 18

High Performance Liquid Chromatography

Question 19

HPLC

Answer 19

similar to TLC
uses packed column
excellent resolution
variety of detectors
may require greater sample conc

Question 20

what does EDX stand for?

Answer 20

Energy Dispersive X-ray spec

Question 21

ESDA

Answer 21

develop indented marks on paper
non-destructive
can provide results from pages up to 5 sheets below

document is first humidified for several mins

Question 22

ESDA process

Answer 22

vacuum switched on

document placed on sample stage and a think mylar film is pulled over the top

the two are intimately held together by vacuum

electrostatic wand moved over stage

• uses a corona discharge wire
• creates static charge across document

glass beads carrying toner powder are then placed on stage

• black toner collects in areas of higher static charge
• indented areas

Question 23

Advantages of ESDA

Answer 23

non-destrictuve
sensitive
inexpensive

Question 24

disadvantages of EDSA

Answer 24

may be affected by fingerprint techniques

may be affected by very high humidity

affected by type of pen used and the pressure applied

Question 25

Paper examination

Answer 25

colour/reflectance
density
thickness
paper type
pH
water marks
chemical composition
-optical brighteners
age

Question 26

UV fluorescence

Answer 26

can be used to distinguish modern papers

used to achieve white than white finish
-post 1950

Question 27

SEM-EDS

Answer 27

scanning electron microscopy

• can be used to examine the fine surface structure of a paper
• commonly used in analysis of historical documents

Question 28

EDS

Answer 28

energy dispersive spectroscopy

can be used to examine elemental compostion

Question 29

radio carbon dating

Answer 29

analysis of 14C ratio of paper

used for historical document verification

Question 30

t=[ln(Nf/No)/(-0.693)] x t1/2

Answer 30

a calculation to do with radio carbon dating and half life