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A Study of Throstle-spun-silk/Raw-silk Core-spun Yarn Part I:Yarn PropertiesY. Matsumoto a , I. Tsuchiya a , K. Toriumi a & K.Harakawa ba Shinshu University , Ueda-shi, Nagano-ken, Japanb Nagoya Institute of Technology , Nagoya-shi, Aichi-ken, JapanPublished online: 01 Dec 2008.

To cite this article: Y. Matsumoto , I. Tsuchiya , K. Toriumi & K. Harakawa (1990) A Studyof Throstle-spun-silk/Raw-silk Core-spun Yarn Part I: Yarn Properties, The Journal of TheTextile Institute, 81:1, 48-58, DOI: 10.1080/00405009008658325

To link to this article: http://dx.doi.org/10.1080/00405009008658325

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A Study of Throstle-spun-silk/Raw-silkCore-spun YarnPart I: Yarn PropertiesY. Matsumoto*, I. Tsuchiya', K. Toriumi*, and K. Harakawa^*Shinshu University, Ueda-shi, Nagano-ken, Japan.^Nagoya Institute of Technology, Nagoya-shi, Aichi-ken, Japan,Received 8.5.1989 Received in revised version 18.7.1989 Accepted forpublication 26.7.1989Throstle spinniiig, or *Gara-bo' spmning, is one of the simplest spinningmethods, and the method of operation is explained. A mechanism for producingthrostle-spun-silk/raw-silk core-spun yam is described. Yam properties arediscussed in relation to three mechanical factors of the machine.

1. INTRODUCTIONTo expand the use of silk, it is desirable to design new yams that have differentproperties from those of traditional yarns, such as raw-silk continuous-filamentand spun-silk yams.

Core-spun yams have special characteristics and are already used in variousapplications. In general, when a continuous-filament core and a staple-fibre skin(or sheath) are combined together in a core-spun yam, the core makes the maincontribution to the tensile properties, and the skin provides the surfacecharacteristics. The present authors have been studying ring-spun core-spunyams in order to improve the stiffiiess of spun-silk fabrics^-^. At present, core-spun yams are produced both by ring spirming and by open-end spinning^.

On the other hand, throstle-spun yam is made from waste fibres, such aswaste cotton and bourette silk, by using the throstle-spinning machine^-^. TheJapariese temi for it, 'Gara-bo spinning*, may be interpreted as 'waste-fibrespinning'. Throstle-spun yam is sofl to handle and has irregular thickness, a lowtwist, and a coarse count. That is to say, throstle-spun-silk yarn may be noil yam,which is an inferior yam of spun silk, and may also be slub yam, which is a typeof fancy yam. The thickness of these yams is characteristically irregular, whichis a fatal defect in nonnal yams. This feature of throstle-spun yam attracted theauthors' attention at this time of diversification of yam qualities.

An attempt was made to produce silk/raw-silk core-spun yams by usingthrostle spinning. An experimental spinning machine was first made, and thecylindrical stuffer tube for silk staple fibres was modified to from the skin layerin the core-spun yam. Furthemiore, the properties of yams produced bychanging the spindle speed, the take-up-roller speed, and the length of ratch inthis spinning machine were examined.

2. EXPERIMENTAL2.1 SpinningFig. 1 is a schematic illustration of the experimental throstle-spinning machine.This machine was designed to enable the spindle speed, the take-up-roller speed,and the length of ratch to be changed. The length of ratch is the distance fromthe centre of the take-up roller to the upper side of the stuffer tube. The rotationof the motor (M )̂ is transmitted to the pulley (F) by the spindle band (C). The

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Fig.l Improved throstle-spinning machine (A: stufFer tube; B:bobbin; C: spindle band; D: ratch;E: photo-displacement sensor; P:pulley; G: guide pipe; L: lever; M,,Mj: motors; Nj.N :̂clutches; R: take-up roller; S: hollow spindle; T: hysteresis tensioner; U: tension meter;W: weight; Y: continuous-filament core-spun yam)

cylindrical stuffer tube (A) is rotated by means of clutches, which are locatedbeneath the lower face of this tube (N^) and on the upper face ofthe pulley (N^).The raw material, a sheet of fibres made by a carding machine, is stuffed in arolled position into the stuffer tube. The spindle fixed in the centre of this tubegoes through the centre of the pulley and touches the lever (L), the length ofwhich is 194 mm. A weight (W) of mass 117.7 g is hung on one arm ofthe lever,and the other arm ofthe lever thus pushes up the spindle. The distance from thefulcrum ofthe lever to the spindle is 60 mm.

In order to start spinning, when the end of a seed yam reaches the staple fibresin the stuffer tube, some staple fibres are entangled with the yam by the rotationofthe stuffer tube. It is possible to introduce twist by rotation one ofthe stuffertube. When the yam becomes stronger by the insertion of some twist, the tubeis lifled up, and the rotation ofthe tube stops. When the yam cannot support thewhole weight ofthe tube, the tube drops down and begins to rotate again. Thethrostle-spun yam is produced by repeating this process.

Yam is drawn out from the upper side ofthe stuffer tube and is wound ontothe bobbin (B), which has a diameter of 107 mm. However, spinning has to beinterrupted for replenishing the stuffer tube when it is empty.

It may therefore be said that the mechanism of yam-making on the throstle-spinning machine is given by:

WL = iT-Y)R

where W is the applied weight hanging on the lever, L is the horizontal distancefrom the fiilcrum ofthe lever to the position ofthe weight, T is the total weightof the stuffer tube, Y is the yam tension, and R is the horizontal distance fromthe fulcrum ofthe lever to the centre ofthe spindle.

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2.2 Improvement of Stuffer TubeA normal stuffer tube, made of tinplate, is about 42 mm in diameter and 250 mmin height, and it has a mass of 110 g when empty. The name 'Gara-bo' spinningoriginates from the clamorous noise *Gara-Gara' in Japanese, caused by therotation ofthe tinplate stuffer tube.

To observe what happens inside the tube, a stuffer tube was made from anacrylic pipe with an inside diameter of 20 mm and a height of 250 mm The massof the improved stuffer tube was 100.6 g when empty. The mass of the rawmaterial was about 5 g.

The normal spindle in the stuffer tube was exchanged for two brass pipes, oneof which was 3 mm in diameter. The other was a guide for the continuous-filament core yam; it was 2 mm in diameter. As shown in Fig.l, the guide pipe(G) was inserted into the hollow spindle (S), the upper end ofthe guide pipe beinginserted into the stuffer tube. The lower end of this pipe was made 16 mm longerthan the hollow spindle, which was 70 mm long. The continuous-filament coreyam was given a core tension by means ofthe hysteresis tensioner (T) and waspassed into the stuffer tube via the guide pipe. In the higher part ofthe stuffertube, some fibres are entangled with the continuous-filament core yam by therotation ofthe stuffer tube. After that, the stuffer tube repeats the up-and-downmovement as mentioned above. In this way, the core-spun yam is produced bythe improved throstle-spinning machine.

2.3 MaterialsThe silk staple fibres used had a mean fibre length of 36.5 mm and formed theskin layer in the throstle-spim core-spxin yam. The continuous-filament coreyam was a twisted raw-silk yam (21 den x 3, 5 turns/in., S).

2.4 MethodsWhen the throstle-spun-silk yam or the throstle-spun-silk/raw-silk core-spunyam was produced by the improved throstle-spinning machine, the spindlespeed, the take-up-roUer speed, and the length of ratch were changed for eachrun. In making yam by the throstle-spinning method, the position of the weightand the core tension should be considered''. For all yams used in this experiment,the weight was placed 28 mm from the fulcrum ofthe lever, and the core tensionwas 20 gf for throstle-spun core-spun yam.

During the spinning process, in which a yam 5 m long was produced, thespinning tension ofthe yam was measured by the tension meter (U) and the up-and-down movement ofthe stuffer tube by the photo-displacement sensor (E).

The English cotton count (Ne)* of a yam seimple was calculated from the meanmass, determined when the test length was 2 m, and the test was repeated 20times.

The twist level was determined 40 times for each sample by using a twist testerwith a sample length of 25 mm.

The thickness irregularity of a yam was measured by an Uster Tester 3automatic evenness tester, in which the yam speed was 25 m/min and the testingtime 1 min. The characteristics tested were the coefficient of variation, yamfaults, such as thin places, thick places, and neps, and the wavelength spectrtun*.

Finally, load/extension curves were obtained by using an Instron constant-rate-of-elongation tensile tester, on which the test length was 200 mm, the rateof extension was 100 mm/min, and the number of tests per yarn was 100.

* This system is normally used in Japan for spun-silk yam and for throstle-spun-silk yam.

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3. YARN PROPERTIES3.1 Yam Count and TwistFig. 2 shows the English cotton count (Ne) of the yams produced plotted against(a) the take-up-roller speed for a constant length of ratch, (6) the length of ratchfor a constant spindle speed, and (c) the length of ratch for a constant take-up-roller speed. The relation between English cotton count and linear density in texis:

linear density (tex) = 590.54 / Ne.

As the take-up-roller speed increased and the spindle speed decreased, the countof the throstle-spun-silk yam and that of the throstle-spun-silk/raw-silk core-spun yam became finer in spite of the fact that the same weight position wasused. The variation in the yam count caused by increasing the take-up-rollerspeed gradually became greater as the spindle speed decreased. As the length ofratch increased, the change in coimt was as follows: when the spindle speed wasconstant, as shown in Fig. 2(c), the yam became finer. Conversely, when both thespeeds were high, as shown in Fig. 2 (c), the yam became coarser. This differencewill be referred to in the later part of this section. In addition, the throstle-spim-silk/raw-silk core-spun yam was finer than the throstle-spim-silk yam.

15

13

• cr

IS

13

11

IS

13

I I

1.8 2.9 4.2 5.3 6.7Tak*-up col lar spaad (rpal

40.8 60.8 73.8Kaicb (cal

.8 60.8 79.8cH (ca)

( t ) Xacch • (21 SpUdla spaad• 130(rpB]

13) Taka-up rol lar•pa«d • (.7(rpal

Fig.2 Variation of yam count (Ne) with machine parameters (spindle speed: O 230 r/min, O540 r/min, • 780 r/min; take-up-roller speed: i9 1.8 r/min, ® 4.2 r/min; throatle-spun-silk yam, throstle-spun-silk/raw-silk core-apun yam).

Fig. 3 shows the number of tums per inch in the yams produced. As the take-up-roller speed increased and the length of ratch decreased, the twist levelincreased. But the effect of spindle speed on twist level was not clear.

Fig. 4 shows the mean spinning tension in each spinning nm. As the take-up-roller speed increased and the spindle speed decreased, the mean spinningtension became smaller, as shown in Fig. 4(a). However, the effect of ratchvariation on the mean spinning tension was not clear.J. Text. Inst., t990, 81 No. 1 © TaUilt InstittiU 5 1

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S >

1.8 2.9 A2 5.3 6.7Taka-up rollcc spaed (zpa)

13

I I A

45.8 60.8 75.6lUtcii {em)

13

1 I

49.8 60.8 75.8Xateh («•)

(1) lueeli • 73. (I) ipaad130(rpa)

(3) Tika-upspaad • (.

Pig.3 Variation of twist with machine Darameters (spindle apeed: O 230 r/min, CB 540 r/min •780 r/min; take-up-roller speed; ^1 .8 r/min, © 4.2 r/min; throatle-spun-silk yam,

throatle-spun-silk/raw-silk core-spun yam).

100 •

9 90 -

1.8 2.9 4.2 5.3 6.7Taka-up roliar ipaad {rpa)

100

« 90

I 80

I 70

£ 60

BO •

100

. ®

45.a 60.8 75.8XaccB (cffll

80

I 70

£ 60

5 0

49.8 60.8 75.8llatcb (CBI

(1) • T3.S(CB} <II Splndla sp.«d- 230(rps)

(3) Taka-up rollar•paad •

Fig.4 Vanation of mean spinning tension with machine parameters (spindle speed: O 230 r/min, (» 540 r/min, • 780 r.min; take-up-roller speed: 181.8 r/rain, "9 4.2 r/min;

throstle-spun-sUk yam, throstle-spun-sUk/raw-ailk core-spun yam).

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A Study ofThrostle-spun-silklRatv-silk Core-spun Yam. Part I: Yarn Properties

70 •

3 50

3 30

70

ja 2 ^ 4.2 3.3 6.7Taka-up roi lar apaad (rpal

• 30

10

0

70 •

90

• 30

10

40.8 60.8 793(CB)

40.8 60.8 79.8lutcli (an)

(2) Spisdla ipM (11 T>Ha'up collaz

Fig.S Variation of rate of rotation with machine parameters (spindle speed: O 230 r/min, <9 540r/min, • 780 r/min; take-up-roller speed: i^l.Sr/min,© 4.2 r/min; throstle-spun-silk yam, throstle-spun-silk/raw-silk core-spun yam).

Fig. 5 shows the rate of rotation of the stuffer tube in each case. The rate ofrotation of the stuffer tube is taken to be the percentage of time during which itactually rotated while the machine made a yam 5 m long. As the take-up-rollerspeed increased, the spindle speed decreased, and the length of ratch decreased,the rate of rotation became higher. In both the mean spinning tension and therate of rotation of the stuffer tube, the throstle-spun-silk/raw-silk core-spunyam had a higher value than the throstle-spun-silk yam.

However, it may be difficult to understand the low rate of rotation of the stuffertube. By increasing the spindle speed and the length of ratch, and by decreasingthe take-up-roller speed, these phenomena may be explained as follows,

(i) When a yam becomes stronger because of the insertion of twist, thestuffer tube is lifted up, and the rotation of the stuffer tube ceases asmentioned above. The minimum twist requirements for lifting the stuffertube must depend on the position of the weight on the lever and on thefibre properties, such as dimensions, the coefficient of friction of singlefibres, and the compressibility of the fibre assembly. At the point at whichthe yam is formed, some staple fibres are withdrawn from the fibreassembly in the tube by both the take-up motion and the weight of thetube. At that stage, some twist may travel downwards from the ratchzone. A yam produced at the higher spindle speed is capable of propagatinghigh twist because the number of turns per unit time is great. Thus theyam is almost always made when the stiiffer tube is raised, and the rateof rotation is then small. On the other hand, a yam produced at the lowerspindle speed is capable of propagating only low twist. Thus the stuffertube immediately drops down and begins to rotate again, and then therate of rotation increases.

(ii) When the take-up-roller speed is low, the stuffer tube does not easily dropdown because of the lower withdrawal speed of staple fibres fi-om thetube. Thus the rate of rotation is small.

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(iii) Finally, the effect of increasing the length of ratch is a decrease in thetake-up-roller speed, because the time taken from the instant of yamformation to the instant when the yam reaches the bobbin becomeslonger and the twist level becomes smaller. Thus the rate of rotation wassmall, and the yam had a coarse count as shown in Fig. 2(c). However,when both the spindle speed and the take-up-roller speed were low, theyam became finer, as shown in Fig. 2(6). This may be explained by thedraft fi-om the weight of the stuffer tube: in a yam, generally, the twistin a thick place is lower than that in a thin place. When the yam isdrafted, only the thick place is affected, and the yam then becomes finer.Thus the method of yam production resembles drafting controlled bytwisting.

As mentioned above, it was observed that, when the mean spinning tensionwas small and the rate of rotation of the stuffer tube was high, the yam madeby using the throstle-spinning machine had a fine count and a high twist. Whenyams were produced under the same spinning conditions, i.e., spindle speed,take-up-roller speed, and length of ratch, the throstle-spxm-silk/raw-silk core-spun yam was finer than the throstle-spun-silk yam.

Furthermore, an attempt was made to calculate the twist factor from the yamcount and the twist level in these yams. Table I lists the over-all mean values ofthe yam count, the yam twist, and the twist factor in the throstle-spun-silkyams and in the throstle-spun-silk/raw-silk core-spun yams. The twist level ofthe throstle-spun-silk/raw-silk core-spun yam was greater than that of thethrostle-spun-silk yam, but the twist factors had almost the same values. Thistwist factor of 3 may be regarded as the optimal value in view of the mean fibrelength of 36.5 mm. This is surprising because the throstle-spun yam is generallysaid to have a low twist.

Table IYam Properties

English Cotton Count (Ne)* Twist (tuma/in.) Twist Factor*

ThroBtle-spun- 11.2 10.2 3.0silk/raw-silkcore-spun yam

Throstle-spun- 9.5 8.8 2,9silk yam

*Linear density (tex) = 590.54/English cotton count (Ne)+Twi8t = Twist factor x (EngUah cotton)"*

3.2 Yam Irregularity3.2.1 Coefficient of Variation of ThicknessFig. 6 shows the coefficient of thickness variation in the yams produced. As thespindle speed increased, the length of ratch decreased, and the take-up-rollerspeed decreased, the coefficient of variation of the throstle-spun-silk yam andthat of the throstle-spun-silk/raw-silk core-spun yam increased. Furthermore,the coefficient of variation of the core-spun yam was greater than that of thethrostle-spun-silk yam.

3.2.2 Yarn FaultsTable II lists the numbers of faults in the yam samples. When the spindle speedwas high, the take-up-roller speed was low, and the length of ratch was short,the number of faults became greater in both the throstle-spun-silk yam and thethrostle-spun-silk/raw-silk core-spun yam.54 J, Text. Inst., 1990, 81 No. 10 TexUk Institute

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30

29

20

'=•1-

\

l.a 2.9 4.2 a.3 6.7Tak»-up rollar sp«ad (rpm)

3S

30

2S

2 0

46.8 60.8 79.8RaCch (cm)

39

30

29

49.8 60.8 79.8Ratcli (CB)

(I) Ratch ' 7S.a(cm) (2) Splndla •twBt« I30(rp«il

(3) Taka-up roller•paad I t.Ttrpa)

Fig.6 Change in coefficient of variation with machine parameters (spindle speed: O 230 r/min,<• 540 r/min, • 780 r/min; take-up-roller speed: •) 1.8 r/min, (&, 4.2 r/min throstle-spun-silk yarn, throstle-apun-ailk/raw-silk core-spun yam).

1-8 ZS *2 03Tu<-uv isllat ••••'

(I) Mick • IJ . I

t O '

7 10

3

40.8 6ae 7S.8

Sfl

t"tr

4C.8 flO.8 7 U

(11 TtU-o* nlUr

Fig.7 Variation of wavelength of maximum amplitude with machine parameters (spindle speed:O 230 r/min, <9 540 r/min, • 780 r/min; take-up-roller speed: S1.8 r/min, iS> 4.2 r/min; -

throstle-Spun-Bilk yam, throstle-spun-silk/raw-silk core-spun yam).

3.2.3 Wavelength SpectrumIn the spectrogram, attention was paid to the wavelength range of 1-100 cm fromthe point of view of statistical significance, the yam test length being 25 m.

Fig. 7 shows the wavelength of the maximum amplitude in the spectrogram.As the length of ratch increased, the wavelength of the maximum amplitudebecame longer on the whole. As the spindle speed increased and the take-up-roller speed decreased, the wavelength of the maximimi amplitude varied asfollows: in the throstle-spun-silk yam, the wavelength became longer; in the

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Table UYam Faults

(1) Difference in Take-up-roller Speed and Spindle Speed

r (r/min)

S (r/min)

Thin places-50%

Thick places+50%

Neps+140%

Neps+200%

NepB+280%

Throstle-spun-Bilk/Raw-silk

Core-spun Yam

2.9 5.3

780 230

70 40

42 18

98 86

17 23

4 6

T: Take-up-roller speed. S: Spindle speed. Ratch

(2) Difference in Ratch

Ratch (cm)

Thin places-50%

Thick places+50%

Neps+140%

Neps+200%

Neps+280%

Throatle-spun-silk/Baw-silk

Core-spun Yam

45.8 75.8

105 46

67 22

96 66

25 18

19 6

2.

780

52

23

81

14

2

Throatle-spun-silk Yam

9 5.3

230

14

9

29

10

2

= 75.8 cm.

Throstle-spun-silk Yam

45.8 75.8

84

27

79

14

1

43

18

67

15

8

Take-up-roller speed = 1.8 r/min. Spindle speed = 230 r/min.

throstle-spun-silk/raw-silk eore-spun yam, on the other hand, the wavelengthbecemie shorter.

This opposite tendency is eharacterized as follows: in the throstle-spiin-silkyam, the wavelength varied because ofthe difference between the methods ofyam formation as mentioned above. Thus, as the rate of rotation ofthe stufiertube decreased, the wavelength became longer. In addition, the yam-formation

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3 0

10

3 0

2 0

3 0

2 0

10

I .a 2.9 4.2 S.3 6.7TmiM-up roller apvad (rpa)

40.8 6O.a 70.8(o)

X H - - -

( I ) • 7s.a(cBi (11 apLndla Ipaada IJO(rpa)

403 60.8lateh (ea)

(31 Taka-up rollar- I.T(rpa)

Fig.8 Variation of maximum amplitude with machine parameters (spindle speed: O 230 r/min,(9 540 r/min, • 780 r/min; take-up-roller speed: ̂ 1.8 r/min, @ 4.2 r/min; throstle-spun-silk yam, throstle-apun-silk/raw-silk core-spun yam).

point moves about around the upper part of the fibre assembly in the stuifer tube.In the throstle-spun-silk/raw-silk core-spun yam, however, the formation pointis hardly capable of moving because the continuous-filament core yam is heldnear the centre of the stuffer tube by the core tension of 20 gf. Hence, when thestaple fibres are entangled with the continuous-filament core yam, the obliquityof fibres is detennined with respect to the yam axis. Without this condition, theyam will not have a good covering of skin around the core. As the position ofwithdrawal of staple fibres moves away from the centre to the outer side of thestuffer tube, the fibre obliquity again becomes greater. Furthermore, when thetake-up-roller speed is low, the length of ratch is short, and the spindle speed ishigh, the fibre obliquity again becomes greater. Thus the wavelength becomesshorter rather than longer.

The over-all mean value of the wavelength of the throstle-spun-silk yam was12.08 cm, and that of the throstle-spun-silk/raw-silk core-spim yarn was 9.85 cm.Thus the maximum wavelength is equal to about three times the mean fibrelength (3.65 cm).

Fig. 8 shows the maximum amplitude in the spectrogram. As the wavelengthof the throstle-spun-silk yarn and that of the throstle-spun-silk/raw-silk core-spun yam became longer, the maximum amplitude became smgdler.

As mentioned above, it was found that, when the coefficient of variation ofthickness in the yam produced by using the throstle-spinning machine wassmall, the spectrogram showed that, when the spindle speed was low and thetake-up-roller speed was high, the wavelength of the maximum amplitude in thethrostle-spun-silk yam was short, and the wavelength in the throstle-spim-silk/raw-silk core-spun yam was long. When the length of ratch was long, thewavelength in both yams was long.

3.4 Tensile PropertiesTable III shows the tensile properties of the throstle-spun-silk yam and that of

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Matsumoto, Tsuchiya, Toriumi, and Harakawa

the throstle-spun-silk/raw-silk core-spun yam. Both yams had a eount of about10 s Ne (59 tex). The eore-spunyam contained approxiniately 12% raw silk and88% staple-fibre silk. Clearly, the throstle-spun-silk/raw-silk core-spuji yamhad an advantage over the throstle-spun-silk yam.

Table mTensile Properties

Throstle-spun-silk/raw-silkcore-spun yam

Throstle-spun-silkyam

Count-Strength Product'

19.4

9.9

Elongation (%)

10.3

6.2

' Count-strength product = Strength (Ibf) x Ne.

4. CONCLUSIONThe properties of yam made by using the throstle-spinning machine wereconsiderably affected by the spindle speed, the take-up-roller speed, and thelength of ratch. For the best perfomiance, the machine should be set up at a lowspindle speed, a high take-up-roller speed, and a long ratch.

In comparison with the throstle-spun-silk yam, the throstle-spun-silk/raw-silk core-spun yam had a fine count and a high twist, but both the yams had atwist factor of about 3, which may be regarded as the optimal value. Furthermore,the throstle-spun-silk/raw-silk core-spun yam had a more irreguJar thicknessand a short wavelength of yam irregularity, but both the yams had themaximum wavelength equal to about three times the mean fibre length.

Now that improved tensile properties have been shown to be possible, theprocess may be developed commercially.

ACKNOWLEDGEMENTSThe authors are grateful to their colleagues Mr N. Kayama, for his co-operationin obtaining the materials, and Mr T. Tanaka, for his collaboration in making thespinning machine.

REFERENCES

' Y. Matsumoto, I. Tsuchiya, and H. Kyuma. J. Seric. Sci. Jpn, 1986,55,451.^ Y. Matsumoto, I. Tsuchiya, and H. K^uma. J. Seric. Sci. Jpn, 1987, 56, 483.^ Y. Matsumoto, I. TBuchiya, and H. Kyuma. J. Seric. Sci. Jpn, 1989, 58, 7.* R. Nield and A.RA. Ali. J. Text. Inst., 1977,68,223.^ S. Wada. J. Text. Rev. Japan, 1942, 33, 521.• H. Yahashi. J. Text. Engng Japan, 1943,11, 63.' Y. Matsumoto, I. Tsuchiya, and H. Kyuma. J. Seric. Sci. Jpn, 1989, 58,1.® R. Furter. "Evenness Testing in Yam Production', the Textile Institute, Manchester, 1982.

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