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Grammar of textile design (Volume c.2) online

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shed " dobby for leno weaving. By reason, however, of open-
shed double-acting dobbies enabhng a loom to be worked at a
greater speed than is possible with " closed-shed " dobbies
(which are necessarily single-acting) it is a common practice to
employ an open-shed dobby for leno weaving. In such cases it
is expedient to equip either the dobby or else the loom with a
suitable auxiliary attachment known as a '* shaking " device, to
•enable the crossing of warp ends to take place as freely as
possible.

Shaking Devices.

§ 109. The function of a shaking device is to facilitate the
crossing of warp ends when forming both cross and open sheds ;
but since it is, under certain conditions, unnecessary to employ
a shaking motion for the reproduction of some leno designs, it



222 GEAMMAE OF TEXTILE DESIGN.

will be useful to indicate when shaking is, and when it is not^
necessary. If either an open-shed dobby (like the " Keighley "
type) or a semi-open shed dobby (like the "Burnley" type) is
employed for leno weaving, with either a top or a bottom-doup
harness, it will be expedient to employ a shaking motion for
designs that require a cross shed to immediately succeed an open
shed, and vice versa ; but such a motion is not required for
designs in which one or more than one pick intervenes between
cross and open sheds as exemplihed in the net leno stripes A,
Fig. 405 ; B, Fig. 407 ; and B, C, Fig. i09 ; because for those
picks, doup threads would be raised by a top-doup harness, and
dejyressed by a bottom-doup harness, and would therefore pass
either from the upper or lower part of the warp shed, respec-
tively, as described in § 108. The reason for this will be mani-
fest after a little reflection upon the circumstances. With a
top-doup harness, cross sheds are formed by depressing doup
threads on the crossed side of their respective standard threads,
which are raised ; and open sheds by depressing doup threads
on their normal side. Therefore, either standard threads should
be lowered, or doup threads raised, at least half-way, to prevent
excessive chafing of crossing threads during the formation of
cross and open sheds. This operation is described as '' shaking ".
With a bottom - doup harness the conditions of shaking are
exactly contrary to those which obtain with a top-doup harness.
§ 110. " Shaking " is effected in a variety of ways, either by
auxiliary attachments fixed either to the loom, or else to the
dobby ; and, as just indicated, it may be accomplished with a
top-doup harness either by raising doup healds, or else by de-
pressing the healds governing standard or regular warp ends
half - way ; and with a bottom - doup harness in a contrary
manner, by depressing doup healds, or else raising standard
threads half-way — the choice being frequently arbitrary One
very simple and common method of shaking depressed healds,
without employing a special leno dobby, is to connect the
required heald stave or staves to one of the arms (which con-
nect the sley with the loom cranks) by means of a suitable
arrangement of levers and connecting rods, as graphically repre-
sented by Fig. 433, in which A represents the loom cranks ; B,



GADZE AND LEJJO FABRICS. 223

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Fig. 438. —Fabric with Mock Leno Stripes.

effects produced by the principle of cross weaving, as described
in the previous sections of this chapter. Mock leno or open-
work effects are sometimes produced alone, but more frequently
in combination with the plain, a twill, satin or other simple
weave, and sometimes with brocade figuring, to produce striped
fabrics which oftentimes bear a very close resemblance to true
leno fabrics. They are also frequently used as ground fillings in
brocade fabrics containing elaborately figured Jacquard designs,
in imitation of leno brocade fabrics produced by a special gauze
or leno harness.



234



GRAMMAE OF TEXTILE DESIGN.



Fig. 438 is a photographic reproduction of an example of
cloth woven with mock leno and warp satin stripes arranged alter-
nately, and will serve to illustrate the realistic leno effects that
may be obtained without employing a leno harness. Mock
leno weaves are of very simple construction, and are chiefly
dependent upon the frequent counterchanging of a suitable
weave, to produce the desired effects. A few examples of these
weaves are given in Figs. 439 to 442. Fig. 439 is a simple
pattern counterchanging on three warp ends and picks, and
therefore repeats on six threads of warp and weft. The counter-
change after the third and sixth warp ends and picks, combined
with the particular method of interweaving them, produces dis-



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Fig. 439.



Fig. 440.



Mock Leno Designs.



tinct gaps or " frets " both lengthwise and crosswise of the fabric^
and thereby creates a decided gauze or leno effect in cloth. The
warp ends may be passed in pairs through each dent of the
reed ; but the leno effect will be emphasised by passing them in
groups of three through each dent, commencing with the first
three warp ends in the design.

Another good mock leno effect is produced by the " canvas "
weave represented in Fig. 440, so extensively employed in the
manufacture of the well-known canvas cloth, usually produced
in coarse textures from strong folded warp and weft, and chiefly
used for the purpose of cross-stitching and other fancy needle-
work. This design is really a further development of that given



GAUZE AND LENO FABRICS.



235



in Fig. 439, and is made to counterchange after every four
threads in both warp and weft, so that the pattern repeats on
eight threads each way. The small perforations characteristic
of this fabric, and through which the needle is inserted (w^hen
employed for fancy needlework), result entirely from the coun-
terchange of the threads. The occurrence of the perforations is
quite incidental to that weave, and therefore unavoidable. If
it is required to introduce the canvas weave as a mock leno
effect, in conjunction with another weave, to form stripes, a
superior effect will result by passing warp ends in groups of four


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Online LibraryHarry NisbetGrammar of textile design (Volume c.2) → online text (page 14 of 19)