2. What is a textile?
• Textile: strictly, this term means “that which has
been woven or may be so” (and so includes
fibres, yarn and thread, as well as woven fabric).
• However, it is also used in a broader sense to
include most non-woven products that are
principally made from fibres, including cordage.
• The number of types is very diverse to meet the
needs of different end-uses
3. 3
Important textile engineering terms
(continued)
Note that, depending on their unit length,
different types of fibre are recognised:
Unit length decreasing
Filament
(long enough
to be
considered to
be of
indefinite
length)
Staple fibre
(long enough
to spin)
Flock
(too short to
spin)
Fibre fly
(very short
airborne fibres
that are
recognisable as
fibres to the
naked eye)
4. Forensic classification of textile evidence
Depend on the size of the item and method of
examination needed:
• Textile trace: evidence is composed of micro traces
which must be examined by microscopical and
instrumental analysis .
– Includes: single fibres, fibre fragments, pillings and small
fibre wads
5. • Textile end-products: are macroscopic evidence.
– examination mainly requires a knowledge of textile
engineering.
– Includes: threads, cords and ropes, clothing, home
textiles, technical textiles
• Textile pattern traces: patterns traced onto and
from textiles
– Includes: damage, imprints, knots
6. Classifying textiles
Textiles can be classified based on their end use:
• Apparel textiles
– Outerwear and underwear, sports wear and leisure
wear
• Household textiles
– furnishings, upholstery, floorcoverings
• Technical textiles: used for their technical
performance and functional properties
7. Subcategories of technical fibres
• medical textiles—for use in hygiene, health, ambulance, surgery,
hospital, etc.
• geo textiles - tents, tarpaulins, awnings
• safety textiles—for protection against heat or cold, chemicals,
radiation, etc.
• transport textiles—for use in motor cars, trains, aircraft,
• industrial textiles—used for the manufacture of technical products
• construction textiles—used for the construction of buildings etc.
• agricultural textiles
8. • Many man-made fibres have technical use
– High performance ones like aramids and carbon
fibres are made almost exclusively for technical
use
9. Manufacture of fibres
Forensic Usefulness of the process
• Textiles are manufactured in batches- there
are slight differences in the batches- not
homogenous
• Plus chemical residues remain on fibres after
processing: can be examined in identifying
fibres
10. Forensic value of Textile relates to the
textile market
• The quantities of the different kinds of
manufactured textiles, and the fibre types used
for them will determine their forensic value
• Global fibre production is of academic interest
only- not essential for forensic practice.
• Fibre production in a particular country or region
is more important
11. Ways of gaining access to fibre market
information
• By creating computerized databases
• Industrial enquires
– Both are equally effective
12. 12
Important textile engineering terms
• Yarn/threads: long, thin textile product made
up of staple fibres and/or one or more
filaments.
14. Single yarns
• are the simplest form of threads.
• They are produced either from staple fibres (fibres of
limited and relatively short length) or from filaments
(fibres of indefinite length).
• A single yarn consisting of staple fibres is described as
spun yarn.
– spun yarn are, in most cases, held together by twist. Spun
yarns are hairy (to a greater or lesser extent).
15. • A single yarn composed of one or more filaments is
referred to as filament yarn.
– Filament yarns usually have a smooth surface.
– Monofilament yarn made from one filament
– Multifilament yarn made of more than one
filament.
– Multifilament yarns may or may not have a twist.
Filament yarns are usually not hairy (ie they are smooth).
16. folded (plied) yarn:
• include all threads in which two or more single yarns are
twisted together in one operation.
• Depending on how many yarns have been twisted
together, one speaks of two-folded yarns, three-folded
yarns, etc.
• Folded yarns for hand-knitting are described as two-ply,
three-ply, etc.
17. 17
Important textile engineering terms
– multiple wound yarn: made by combining, without
twisting, two or more component yarns (which may or
may not be similar) together.
– two or more single or folded yarns wound together
parallel (plied) without being twisted together.
18. Cabled yarn:
• Cabled yarns include all threads which are composed of
two or more folded yarns twisted together in one or more
operations.
• There is >1 twisting operation involved.
• The component yarns may or may not be similar
20. Textured Yarns
• texturing is done to filament yarns.
• Texturing is a process which introduces
durable crimps, coils, loops or other
distortions along the filaments.
• There are many different texturing methods.
– Most of them depend on the thermoplastic
properties of the filaments
21. • Texturing brings bulkiness, elasticity and warmth,
water absorbency into a filament yarn and affects
the textile handle (the feel) of the fabric, making
the cloth manufactured from it more comfortable
to the wearer.
• In the case of textured filament yarns, the
morphology of the crimp is of interest to the
forensic fibre examiner.
– The term 'crimp' means the waviness of the fibre. It
can be expressed numerically as the crimp frequency.
22. Fancy Yarns
• Fancy yarns are single and folded yarns with
deliberately produced irregularities in their
construction.
• Such irregularities could be spirals, gimps, loops,
snarls, knops.
• E.g. bouclé, tweed, slub, nub chenille
23. Bouclé yarns
• are compound yarns comprising a twisted core
with an effect yarn around it, producing wavy
projections on its surface.
• To make bouclé, at least two strands are
combined, with the tension on one strand being
much looser than the other as it is being plied,
with the loose strand forming the loops and the
other strand as the anchor
28. • Fibrillated yarns are produced by a process of
fibrillation.
• Fibrillation is the process of splitting fibres
longitudinally into a network of interconnected fibres.
• The fibrillation process can be a random splitting,
giving a relatively coarse network, or a controlled
splitting to give finer network, e.g. by rapidly rotating
pinned rollers.
• Fibrillated yarns are mainly used for cordage or
technical textiles reinforcement PP textile used in
concrete.
30. Importance of yarn structure to
forensic scientist
• Knowledge of the basic construction of the yarns
in a fabric is necessary in order to be sure that a
representative sample of comparison fibres has
been taken from a fabric undergoing
examination:
– The single yarns in a multiple wound yarn
– a folded yarn or a cabled yarn may be processed from
different fibre types.
• Therefore, fibre samples must be taken from each single
component of these kind of yarns.
31. Why are textiles important to the
Forensic scientist?
• Forensic examination of woven fabrics should not
be focused on the type of weave alone.
• Often the fabric construction provides more
valuable information, represented by the number
of warp ends and filling picks per centimetre.
32. Twist Direction
• Twist is described as S or Z according to which
of these letters has its centre inclined in the
same direction as the surface fibres of a given
yarn.
• The yarn must be viewed vertically when
determining twist.
33. Twist frequency
• Twist level refers to the amount or number of
twists per unit length of a yarn.
34. Categories of textiles
• Fabrics composed from yarns are the most
common category.
– Woven fabrics and knitted fabrics belong to this
category,
– as do laces, bobbinets/tulle, braids, nets, stitch-
bonded fabrics, scrims/gauze and adhesive-
bonded or heat-bonded thread sheets.
35. • Fabrics made directly from fibres are another
important group,
– including three sub-classes of textile products: felts,
nonwovens and wads. Fibres bonded together by heat and
mechanical force.
• Combined bonded fabrics is the general term for the
third category of textile fabrics.
– From the forensic scientist's point of view, most types of
fabric in this category are specialties. E.g. interfacing, J
cloths, wet wipes, surgical gowns
– made from webs of synthetic fibres bonded together with
heat and adhesives.
36. Woven Fabrics
• Woven fabrics are defined as fabrics composed of
rectangularly interlaced threads—the warp threads
and the weft threads.
– The warp threads, or the warp, are oriented
lengthways in the fabric
– weft threads, or the weft, have been
introduced widthwise into the fabric.
• An individual warp thread is described as an end,
an individual weft thread as a pick.
37. Characteristics of woven fabrics
• Woven fabrics fray at the edges
• They are firm and do not stretch much
– Least stretch along the bias (warp thread)
38. Types of weaves
• The pattern of interlacing of warp and weft is
described as the weave of a woven fabric.
• Three types of basic weave can be
distinguished:
– the plain weave,
– twill weave and
– satin (atlas) weave
• Many subtypes exist
39. • The repeat is the smallest
number of ends and picks on
which a weave interlacing
pattern can be represented
40. Plain weave
• Plain weave is the simplest and most frequently used
interlacing weave.
• The plain weave has the smallest repeat.
• The odd warp threads operate over one and under one
weft thread throughout the fabric,
• The even warp threads reversing this order to under
one, over one, throughout.
• very common kinds of woven fabrics, such as batiste,
calico, chiffon, chintz, cretonne, muslin, panama,
poplin, repp and taffeta, are plain-woven fabrics.
41. • The plain weave looks
the same on both sides
43. • Plain weave is particularly used in the manufacture of flimsy
fabrics which require less fibre mass, such as fabrics for
blouses, shirts and other end-uses in the clothing area.
– The plain weave is also applied for a wide variety of woven
fabrics with end-uses in household and technical textiles.
• This weave is not as strong as the twill weave, thus causing
the garment being easily torn, wrinkled, and wears much
quicker than the other weaves.
• As a plus, “plain weave” fabrics are not as absorbent as
twill or satin woven fabrics because of the tightness of the
weave making them perfect for shedding moisture like light
rain.
44. Twill weave
• Twill weave is a weave that repeats on three or more
ends and picks.
• Each wire is passed alternately over two and then
under the next two cross wires
• This kind of weave produces diagonal lines on the
surface of fabric.
• The direction of the twill is generally described as the
fabric is viewed looking along the warp. By analogy
with the twist direction in yarns, a Z-twill and an S-twill
can be distinguished.
47. • Apart from the twill direction, a twill-weave can be
characterized by whether the warp or the weft
predominates on the face (side with most wales or
patterns) of the fabric:
– warp-twills and
– weft-twills (twillette)
– even-sided twills (Batavia weave), where the warp and
the weft are balanced in face of the fabric.
48.
49. • Twilled fabrics contain a high fibre mass-because
of fewer interlacings, yarns can be packed closer.
• Their durability and wear resistance is greater
than that of plain-woven fabrics-due to high fibre
mass
• Industrial clothing and work-wear are therefore
one of the domains of twilled fabrics.
• most common kind of twilled fabric is denim
– Gabardine and herringbone twill are two other
commercial names for twilled fabrics.
52. Satin weave
• Satin weave is also known as atlas weave. This
weave produces a smooth surface, free from
twill (ribs or diagonals).
• There are two generic types of satin weave,
resulting in weft-faced and warp-faced fabrics:
– sateen/weft
– satin/ warp.
53. • A satin weave is characterized by floats ( the length of a
warp thread or a weft thread on the surface of the fabric
between two adjacent intersections).
• The length of the float corresponds to the number of
threads which the intersecting yarn passes.
• In a satin weave, a floating yarn traverses at least four
yarns.
56. • the satin weave allows the possibility of
incorporating an expensive textile material in the
face of a fabric and a less expensive material in
the back.
• Because of the floats, a satin or sateen fabric is
less abrasion-resistant if fine yarns have been
processed.
• The satin weave is often found in fine table-linen
and bed-linen as well as in clothing materials.
57. Identifying the warp
Indicators for the warp direction:
• striped patterns made by coloured yarns in fabrics
are predominantly oriented in the warp direction
• in checked fabrics, the 'squares' are often not
really square, but slightly rectangular—the longer
sides of the rectangles indicate the warp direction
• the elasticity of a fabric is often lower in the warp
direction than in the weft direction
• the warp threads are mostly finer yarns with a
higher twist and a higher tenacity than the weft
threads
58. 58
Knitted fabrics
• Knitting is the creation of fabric by interlocking loops of
yarn, either by machine or by hand.
• There are two fundamentally different types of knitting:
warp knitting and weft knitting.
59. 59
Weft knitting
• Weft knitting is conventional knitting, we will
consider this in more detail
• The basic unit of all knitting is the knitted
loop. This has three parts:
63. • Weft knitting is regarded as normal knitting.
• The fabric-forming loops travel in a weft-wise
direction across the width of the fabric.
• Weft threads are more or less at right angles to
the direction in which the fabric is produced.
64. 64
Weft knitting
• Within knitted fabric, a given loop can be described
as being part of a course (ie part of a row of loops
that runs across the width of the fabric) and part of
a wale (ie part of a column of loops that runs along
the length of the fabric).
• The number of courses per unit length (the course
density) and wales per unit length (the wale
density) give two points of comparison between
two knitted fabrics.
67. 67
Weft knitting
• A knitted fabric can have one of many different
constructions.
• The simplest and most common of these is the plain
jersey construction.
• The front of which appears to be stacked columns of
“v” shapes, whilst the back looks like stacked waves.
•
• The origin of this difference is shown on the following
two slides:
70. Warp knit
• In this technique, the fabric-forming loops travel
in a warp-wise direction down the length of the
fabric, parallel to the selvedges.
• Therefore, a warp-knitted fabric is composed of a
lot of wales (columns of loops) along the length
of the fabric.
• Each warp thread is more or less in line with the
direction of fabric production.
71.
72. Loops are formed across the
width of the fabric
Loops are formed vertically
down the length of the fabric
73. 73
Important textile engineering terms
• Thread: any yarn with a diameter <4 mm.
• Cordage: round cross section product, with a
diameter of > 4mm, that is made from yarn.
74. 74
Key rope making terms
• Strand: a basic rope component made by
twisting a number of yarns together.
• Rope: flexible textile product that has a high
length to diameter ratio, that is made up of > 2
strands twisted (or plaited) together and that has
a diameter of at least 4 mm.
77. 77
Key rope making terms
• Twine: flexible textile product that has a high
length to diameter ratio, that is made up of > 1
strands twisted together and that has a diameter
< 4 mm.
• Core: central yarn that, while not structurally
combined with a rope or twine, runs throughout
its length
78. 78
Key rope making terms
• Lay: the direction of twist of the component
strands of a helical rope or twine (S lay and z lay,
see earlier).
• Length of lay: one complete turn of a strand that
is part of a rope or twine.
• Angle of lay: see upcoming slide
82. 82
Some key points of comparison in
rope examination
• Comparative light microscopy
• “House markers”
– unlike garments, few ropes have labels stating who
made them.
– Some manufacturers therefore include recognizable
yarns (“house markers”) in one or more of the strands
of the rope.
– Beware, cheap copies of expensive ropes may include
“fake” house markers.
83. 83
Some key points of comparison in
rope examination
• Colour coded fibre types.
– Brown = polypropylene
– Orange = polyethylene
– Blue = polyester
– green = polyamide
– red =sisal
– black = manila
– green = hemp
Beware, not all rope fibres will conform to this helpful
code!
84. 84
Some key points of comparison in
rope examination
• Jigsaw fit (often impossible because of fraying)
• Knots
• In natural material (ie not man-made)
– Microscopic morphological features of ashed material
– Microscopic morphological features of macerated material
• In man-made materials
– polarised light microscopy
– IR spectroscopy
– melting point
– density
