Knitting technology, Third Edition

Fig. 23.6
Open and closed lap pillar stitches.

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Basic warp knitting principles
295
more horizontal appearance, whilst overlaps produced by the same thread 
will be separated from each other at successive courses by an extra wale in 
width.
3
Atlas lapping
(Fig. 23.7). This is a movement where the guide bar laps progres-
sively in the same direction for a minimum of two consecutive courses, normally
followed by an identical lapping movement in the opposite direction. Usually,
the progressive lapping is in the form of open laps and the change of direction
course is in the form of a closed lap, but these roles may be reversed. From the
change of direction course, tension tends to cause the heads of the loops to
incline in the opposite direction to that of the previous lapping progression. The
change of direction course is normally tighter and the return progression courses
cause reflected light to produce a faint, transverse shadow, stripe effect.
The underlaps on the technical back give the appearance of sinker loops in a
spirally weft knitted structure. With a single guide bar having different coloured
warp threads, zigzag effects can be produced. This is sometimes termed 
single
atlas
or 
vandyke
. More elaborate geometrical patterns can be achieved with pat-
terned warps using atlas lapping on two or more guide bars. Atlas is also the
base for many simplex and all Milanese fabrics.
Cohesive single guide bar structures (Fig. 23.8a, b) may be knitted using a single,
fully-threaded guide bar producing underlaps and overlaps. However, these are
seldom commercially viable because of their flimsiness, low strength, lack of stabil-
ity, poor covering power, distortion caused by loop inclination, and limited pat-
terning potential.
Loop inclination is caused by the underlaps of the guide bar entering and leaving
the head of the needle loop from the same side and thus producing an unbalanced
tension from that direction (unlike weft knitting where the sinker loops enter and
leave from opposite sides of the head of the loop).
A more balanced tension is achieved by having two sets of warp threads under-
lapping in opposition to each other so that the underlaps of each enter and leave
Fig. 23.7
Atlas lapping.

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296
Knitting technology
from opposite sides of the head of the loop. For these reasons, the simplest warp
knitted structures are usually composed of two sets of warp threads, and most
machines have a minimum of two guide bars.