Theory of Silk Weaving - Part 1
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Theory Of Silk Weaving.by Arnold Wolfensberger.PREFACEThe silk industry of America has of late years rapidly advanced to thefront rank among the great textile industries of the world. It may indeedbe proud of this position, to which that enterprising spirit and untiringenergy peculiar to our nation, combined with our great technical andnatural resources, has brought it.That we are, on the other hand, not yet at the height of perfection we arealso compelled to acknowledge, but if we consider the short s.p.a.ce of timethat the American industry has required for its development, as compared tothe decades, almost centuries, to which some of the great European silkcenters can look back, the fact is neither surprising nor discouraging.While it must not be our aim to imitate or copy their ways, inasmuch as outconditions and circ.u.mstances are quite different from theirs, we may stillprofitably study their methods in order to overcome our deficiencies.The greatest advantage which our compet.i.tors derive from such a longexistence consists in having at their disposal a force of skilful, trainedhelp. The manufacturers, appreciating the importance of this factor, makegreat efforts and pecuniary sacrifices to elevate and maintain the highstandard of their industry.For instance, they support textile schools and lecture courses, where youngmen can acquire a thorough technical education and equip themselves for acareer of usefulness, thereby serving their own interests and at the sametime furthering those of their chosen profession. [Page 6]This beneficial influence cannot fail to exert itself from the standard ofthe higher employer down to that of the weaver, who would naturally takemore pains and interest in his work than if he were a mere mechanicalappendage to his loom in order to keep it in motion.Very little has been done in his country for technical education as far asthe silk industry is concerned, and it was on this special branch, thatprompted the author to offer in the present little work a treatise on thetheory of shaft weaving for broad silks and ribbons.It is divided into three princ.i.p.al parts: #1st. Drawing-in the warp in the harness. 2nd. The weaves and their application. 3rd. Decomposition or a.n.a.lysis of the cloth.#To the foregoing there have been added in the revised and enlarged editionseveral additional parts covering the following: JACQUARD WEAVES, BOX LOOMWEAVES, including CREPES, and COST CALCULATIONS for plain and fancy weaves.The subject while condensed, is made as clear and comprehensible aspossible, and to many desirous of increasing their knowledge in thisdirection, this should prove a valuable help.The author, through the medium of this work, hopes to win the approval andencouragement of the manufacturers, and will feel amply repaid should hisefforts tend to develop a deeper interest in the "Queen of Textiles." * * * * * [Page 7]THEORY OF SILK WEAVINGDRAWING-INWith this term we designate the operation preceding the weaving, by whichall the warp-threads are drawn through the heddles of the harness.The order in which this is done varies according to the weave and thenature of the fabric to be produced; so we distinguish: #Straight draws, Skip draws, Point draws, Section draws.# * * * * *STRAIGHT DRAWS[Ill.u.s.tration: Fig. 1] * * * * [Page 8][Ill.u.s.tration: Fig. 2]These form the simplest and most common method of drawing-in. We begin withthe first heddle on the left side of the shaft _nearest to the warp-beam_,then take the first heddle of second shaft and so on until all the shaftsthe set contains are used in rotation. This completes one "draw," and thisoperation is repeated until all the warp-threads are taken up.The method of making the shaft nearest to the warp-beam the first, isalmost universal with the silk business and is technically called_drawing-in from back to front_.The opposite, or drawing in from _front to rear_, is used occasionally,however, and in this case makes the first heddle on the left hand side ofthe front shaft No. 1.The making out of the _Drawing-in Draft_, which must indicate thearrangement or the rotation in which the warp-threads are drawn in, can bedone in various ways, of which we will mention the two most popularmethods. The first is by using common designing paper, and indicating therotation by dots. The horizonal rows of squares represent the shafts, thevertical rows the warp-threads. Fig. 1 shows four repeats of a straightdraw on six harness marked out according to this idea. A second method isto use paper ruled horizontally, the lines representing the shafts; and todraw vertical lines for the warp-threads. The latter are made to stop on [Page 9]the lines bearing the number of the shafts into which the respectivethreads are to be drawn. Fig. 2 is such a draft, ill.u.s.trating six repeatsof a draw on four harness from "Front to Rear." * * * * *SKIP DRAWS[Ill.u.s.tration: Fig. 3] * * * *[Ill.u.s.tration: Fig. 4]The draws coming under this heading are used very extensively in silkweaving, especially for fabrics requiring a heavy warp and a large numberof shafts. Enter first the odd and then the even shafts. An 8 harness drawof this kind, of which three repeats are shown in Fig. 3, runs as follows:1, 3, 5, 7, 2, 4, 6, 8.Fig. 4 is a 12 harness draw of the same cla.s.s. * * * * *POINT DRAWS[Ill.u.s.tration: Fig. 5] * * * * [Page 10][Ill.u.s.tration: Fig. 6] * * * *[Ill.u.s.tration: Fig. 7] * * * *[Ill.u.s.tration: Fig. 8] * * * *[Ill.u.s.tration: Fig. 9] [Page 11]Point draws are a combination of a regular straight draw from back to frontand one from front to back, the first and the last shafts only being usedonce, while the rest receive two ends each in one repeat of the draw. Fig.5 ill.u.s.trates a regular point draw in 2 repeats on 10 shafts. It will beseen that 14 ends make a repeat; in fact, the number of warp-threadsrequired for one draw will always be double the number of harness less 2,hence a 12 harness regular point draw will require 22 warp-threads for arepeat.The drawing-in draft ill.u.s.trated in Fig. 6 is a slight variation of theregular point draw; it consists, as will be seen, of a draw from back tofront, and also a full one from front to back, there by causing a _doublepoint_.Another change from the regular point draw is ill.u.s.trated in Figs. 7 and 8;this cla.s.s may be called _Broken point draws_, because a new draw is begunbefore the other one is complete. Fig. 9 also comes in this cla.s.s andrepresents a _zigzag draw_ on 10 harness.The drawing-in drafts which we have described under the head of "Pointdraws," are used mostly to obtain the various pointed and zigzag effects. * * * * *SECTION DRAWS[Ill.u.s.tration: Fig. 10] * * * * [Page 12][Ill.u.s.tration: Fig. 11] * * * *[Ill.u.s.tration: Fig. 12] * * * *[Ill.u.s.tration: Fig. 13] * * * *[Ill.u.s.tration: Fig. 14] * * * * [Page 13][Ill.u.s.tration: Fig. 15]This division of drawing-in drafts is used extensively in silkmanufacturing; for instance, in all fabrics having a ground warp and abinder warp, also in double-face goods, or where two different weaves arecombined in one effect.One or more threads are drawn on the first section, then one or more on asecond and third, if the harness is divided in so many sets.The following examples will ill.u.s.trate the principle of these draws.In Fig. 10, shafts 1, 2, 3, 4 from the first set, shafts 5 and 6 thesecond, 8 threads are drawn straight on the first, then 2 on the secondsection.Fig. 11, first set shafts 1 to 6 inclusive, second set shafts 7 and 8.Fig. 12 is drawn end and end on two sections having 8 shafts each.Figs. 13, 14 and 15, while not strictly belonging to the cla.s.s of sectiondraws, may, however, be considered under this heading. The idea is to drawa certain number of ends in one part of the harness and another group inanother part, be it straight, point or skip, which will cause the effect onthe cloth to be accordingly transposed or broken up. [Page 15] * * * * *THE WEAVES AND THEIR CONSTRUCTIONIn any woven fabric we distinguish two systems of threads, the _Warp orChain_, running lengthways in the cloth, and the _Filling or Weft_,crossing the former at right angles.This crossing or interlacing consists of every individual warp-thread beingplaced alternately under and over one or more threads of the fillingsystem. The arrangement of this interlacing is technically called the_Weave_, and the variety in which the points of crossing can be distributedis practically endless.It is princ.i.p.ally the weave that lends to a fabric its character,influenced, of course, by the material used, the size and tension of thethreads and the combination of the colors.The weaves are divided into three main cla.s.ses: _the Foundation weaves_. Inthe silk business they are known under the following names: #The Taffeta Weave, The Serge Weave, The Satin Weave.#In the foundation weaves each thread effects only one crossing in onerepeat of the weave, and the points of interlacing occur in a givenrotation. A repeat in the foundation weaves comprises the same number ofwarp-threads as of _picks_ or filling threads, and if this number is 8, for [Page 16]instance, the weave is called an 8-shaft or an 8-harness weave. In markingout a weave, the warp-threads are represented by vertical lines, thefilling by horizontal ones, or in each case by the s.p.a.ce between theselines. The places where a warp-thread lies over the filling are marked withpaint or simply with a cross. In a similar manner we mark out the _chaindraft_, which indicates the rotation in which the shafts are raised. * * * * * [Page 17]THE TAFFETA WEAVE[Ill.u.s.tration: Fig. 16] * * * *[Ill.u.s.tration: Fig. 17] [Page 18]This is the simplest and oldest method of interlacing. The odd numbers ofwarp-threads cross the even numbers after every pick; hence of twowarp-threads one will always go over the first pick and under the second,and the other end under the first and over the second pick. Taffeta cloth,therefore, has the same appearance on both sides, and in cotton and woolweaving this weave is technically--and properly indeed--called the _PlainWeave_. It has the smallest repeat, 2 warp-threads and 2 picks, and theexchanging of warp and filling is the most frequent possible. The cloththus produced is firmer and stronger than that obtained with any otherweave.Fig. 16 is a taffeta on 4 shafts straight draw, the draft executed in themanner which we have already mentioned in explaining the drawing-in drafts.Fig. 17 on common designing paper, ill.u.s.trates a taffeta made on 8-harness,skip draw.Be it mentioned that the drawing-in draft and the chain draft will be addedthroughout this work, the former over the weave to correspond with therespective warp-threads, the latter to the right of the drawing-in draft. * * * * * [Page 19]GROS DE TOURS WEAVES[Ill.u.s.tration: Fig. 18] * * * *[Ill.u.s.tration: Fig. 19]In this weave the working of the warp is the same as in taffeta, exceptthat instead of one pick, two or more are inserted in the same shed. It ismostly used in selvedges, where it serves to give more firmness to the edgeof an otherwise loosely woven cloth, and prevents the weaving ahead of theedge in a tight weave. Gros de Tours is sometimes used, especially whencotton or wool filling is employed, with a view to lay two picks nicelyside by side, whereas a thread entered two ply with the taffeta weave willalways receive some twist, which may disturb the perfect evenness of thefabric.Fig. 18 is a Gros de Tours with two picks on four harness straight through.Fig. 19 ill.u.s.trates this weave with three picks drawn end and end on twosections of four shafts each. * * * * * [Page 20]SERGE or TWILL WEAVESWhile the taffeta weave produces either an entirely smooth fabric, or onewith a distinct transverse rib as in gros-grain, the twill weave formsdiagonal lines on the cloth, running either from left to right or fromright to left.To make a twill, not less than three ends and three picks are required, ofwhich each thread floats over two of the other system and interlaces withthe third. The rotation of the interlacing is always consecutive, that isit moves with each succeeding pick one thread to the right (or to the leftif the lines are to run in that direction). If warp and filling have thesame texture, that is the same number of threads in a given s.p.a.ce, thetwill lines will form an angle of 45; if the warp stands closer than thefilling, the incline will be steeper, and in the opposite case the anglewill approach more the horizontal.The weaves can be expressed in numbers, for instance: the 3-end twill warpeffect would be marked 2-1, which indicates that each warp-thread goes overtwo and under one pick.Twill weaves are called _evensided_ when the arrangement of "warp up" and"filling up" are evenly balanced, and _unevensided_ if either warp orfilling predominate on the face of the fabric; the latter cla.s.s istherefore subdivided in _Warp effects_ and _Filling effects_.In the following a number of serge weaves are ill.u.s.trated, the Frenchdesignations being added in some cases, as they are still extensively usedin the trade. [Page 21] * * * * *FILLING EFFECTS_Satin de Lyon,_ 2-1.On 6 harness straight through.[Ill.u.s.tration: Fig. 20] * * * *_Levantine,_ 3-1