This document discusses purl and interlock knit fabrics. It begins by defining purl fabric as having alternating knit and purl courses that create loops in opposite directions. Purl fabric is produced on special purl machines using double-headed needles that transfer between beds. Interlock fabric is made from two interlocked 1x1 rib structures that create a reversible fabric with technical faces on both sides. Interlock is produced on circular or flatbed machines using long and short needles and two feeders to knit separate half courses. Examples of applications for each fabric type are given.

1. 22/KNITTING VIEWS/MAY-JUNE 2011
VASANT R KOTHARI has done Master’s in Textiles Technology from DKTE’s Textile and Engineering Institute,
Ichalkaranji (Shivaji University, Kolhapur), Maharashtra. He has also done Diploma in Export Management (Apparel
Export) from the Indian Institute of Export Management, and Garment Export and Merchandising Management
from NIFT, Bangalore. Presently, he’s working as an Assistant Professor in Department of Fashion Technology,
NIFT, Bangalore. (This is his ninth input from the series of articles in Knitting Views).
Purl fabric
The Purl fabrics are also known as link-
linkfabrics.Purlwasoriginallyspelt‘pearl’
and was so named because of its similar
appearance to pearl droplets. In purl, the
loops of one course are intermeshed in
one direction and the loops of the next
course intermeshed in opposite direction,
i.e. the alternate courses having face and
back loops. It means each wale contains
both knit stitches and purl stitches. This
differs from the rib fabric, in which the
wales contain either knit or purl stitches.
A simple purl fabric looks somewhat like
the back of a jersey knit on both sides of
the fabric. The simplest purl fabric is
Fig 9.1: The technical face of purl fabric
Fig 9.2: 1 x 1 purl fabric
Fig 9.3: Face and back side of
plain jersey fabric
known as 1 x 1 purl, in which one course
has all knit stitches and the next course
has all purl stitches. The cycle repeats on
the third course.A2 x 2 purl knit fabric is
made with two courses of knit stitches
followed by two courses of purl stitches.
Fig 9.5: Knitting notation of purl fabric
Fig 9.4: Face side of the fabric
Cross
section
Back side of the
fabric

2. KNITTING VIEWS/MAY-JUNE 2011/23
Fig 9.9: Interlock fabric structure
Fig 9.6: Circular and flatbed purl
knitting machine Fig 9.8: Purl needle transfer action
Production of purl fabric
Purl-knit fabrics are made on knitting
machinescalledpurl-knitmachinesorlinks-
and-links machines. The purl knitting
machines are basically of flat and circular
types as shown in fig 9.6. The flat is having
two horizontal beds for needle movement
and central gap for fabric formation. The
circular type has two cylinders, one above
the other and thus referred as super
imposed cylinder machine. As stitches are
sometimes drawn to the front and
sometimes to the back, two sets of needles
arerequiredtoproducethesefabrics.Inpurl
machines,however,ratherthantwodistinct,
separate sets of needles, one set of double-
headed latch needles is used as shown in
fig9.7.Thetwoneedlebedsareinalignment
with each other. The double headed needles
movefromoneneedlebedtotheother,from
side to side of the knitted fabric as it is
produced,alternatelymakingstitchesonone
fabric side and then the other.
The purl-knit machines used to produce
purl knit fabrics are the most versatile
industrial knitting machines. These
machines can produce plain and rib as well
as purl fabrics. By selective programming
of needle motion, fabrics of all three types,
sometimes with unique design effects are
possible. Purl-knit machines are widely
used in the sweater industry.
Although extremely versatile, the purl knit
machines have the lowest rate of
production of all knitting machines.
The knitting action
Fig 9.8 shows the knitting action of a
flatbed purl machine which has tricks in
each of the needle beds. They are in line
with one another to enable the transfer of
purl needle from the control of a slider in
one bed into the control of a slider in the
opposite bed.
Position 1 shows engagement of the head
of the receiving slider with the needle hook
that was originally knitting from the
opposing bed. In position 2, the needle
has been moved to the centre, with both
sliders engaging the needle hook. The
sliders then start to move back, but the
slider in the back bed is pressed down by
a cam, so that front bed slider is freed from
the needle hook and the needle is
transferred to the back bed.
In position 3, the slider in the back bed has
control of the needle and it can be seen that
the yarn is fed to the opposite end of the
needle, when compared to that of position
1.Thenthesliderinthebackbedhasmoved
the needle to knock over position to
complete the formation of the purl stitch.
It should be noted that a purl stitch is made
when a loop is formed by one hook and
then at the next course by the other hook
of the same needle, so that one course is
formed on the front bed and the next
course is formed on the back bed to create
a 1 x 1 purl structure.
Fabric characteristics
To identify a purl-knit fabric, fabric need
to stretch in its length direction. The
appearance of alternating rows of knit
stitches and purl stitches in the course
direction is evidence of a purl knit.
Generally purl-knit fabrics tend to lie flat
and do not curl as do jersey knits. Purl
fabric has same appearance in face and
back. It can unroved from either end.
Lengthwise extension is more as compare
to width wise and hence purl fabric
contract towards the centre in a course
wise direction. Thickness of fabric is two
to three times more as compare to single
jersey fabric.
The fabric is commonly used for children’s
wear and sweaters.
Interlock fabric
Interlock-knit fabrics are a variation of rib
knits made on the interlock machine.
Interlock is an interlocking of two 1 x 1 rib
structures in such a way that the face wale
of fabric “1” is directly in front of the
‘reverse wale’ of the rib fabric “2”.
Interlock has the technical face of plain
fabric on both sides, but its smooth
surface cannot be stretched out to reveal
the reverse meshed loop wales because
the wales on each side are exactly opposite
to each other and are locked together as
shown in Fig. 9.9. Each interlock pattern
row (often termed an ‘interlock course’)
requires two feeder courses, each with a
separate yarn that knits on separate
alternate needles, producing two half-
Fig 9.7: Double headed latch needle
Therefore, the cost per pound of fabric
produced is highest for purl knit fabrics.
Knitting machines for jersey knits have
the highest productivity but the lowest
versatility. Productivity for rib-knit
machines falls between those for jersey
and purl machines.

3. 24/KNITTING VIEWS/MAY-JUNE 2011
Production of interlock fabric
Interlock is produced mainly on special
cylinder and dial circular machines and on
some double-system V-bed flat machines.
In interlock machine
• Interlock gating, the needles in two beds
being exactly opposite each other so
that only one of the two can knit at any
feeder
• Both, the cylinder and dial beds should
have two types of needles viz., long and
short needles
• Alternate placement of long and short
needles in both the beds is required
• The long needle of one bed should face
the short needle of the other bed and
vice versa
• Two separate cam systems in each bed,
each controlling half the needles in an
alternate sequence, one cam system
controlling knitting at one feeder, and
the other at the next feeder
• Needles set out alternately, one
controlledfromonecamsystem,thenext
from the other; diagonal and not
opposite needles in each bed knit
together
• Minimum of two yarns are required to
knit one interlock course and hence a
minimum of two feeders supply
• The knitting style is in such a manner
that only long needles of dial and
cylinder will knit with the first feeder
and only short needles of dial and
cylinder will knit with second feeder
Fabric characteristics
To determine whether a fabric is an
interlock or a rib, spread the fabric width
wise, and view the fabric wales carefully
at the top edge of the cloth. If the knit
stitches are one behind the other, the
fabric is interlock. If the wales of knit
stitch alternate, the fabric is rib.
Interlock fabric is a reversible balanced,
smooth, stable structure that lies flat
withoutcurl.Like1x1rib,itwillnotunrove
from the end knitted first, but it is thicker,
heavier and narrower than rib of
equivalent gauge, and requires a finer,
better, more expensive yarn.
It unroves from the course knitted the last.
The fabric becomes costlier due to
thickness and less production. Interlock
is used for outwear fabrics, often using
wool, acrylic and polyester yarns, while
cotton and polyester/cotton blends are
used for the production of underwear
fabrics. Interlock fabrics are also popular
for blouses, dresses, and dressy T-shirts.
Their dimensional stability and the fact
that they do not tend to easily stretch out
of shape contribute to these popular uses.
Interlock fabrics offer a smooth surface
for printing by both screen and heat-
transfer methods
In the next article, we would be discussing
about straight bar knitting machine.
(The Author can be contacted at
www.vasantkothari.com)
Fig 9.17: Interlock cam system
gauge 1 x 1 rib courses whose sinker loops
cross over each other. Thus, odd feeders
will produce alternate wales of loops on
each side and even feeders will produce
the other wales.
Fig 9.16: Graphic representation of two sets
of needle on interlock knitting machine
Fig 9.15: Knitting notation of interlock fabric
Fig 9.10: Interlock fabric structure
Fig 9.11: Interlock fabric structure
Fig 9.12: Front view of interlock fabric
Fig 9.13: Back view of interlock fabric
Fig 9.14: Cross section
view of interlock fabric