ISO 21046:2018

INTERNATIONAL ISO
STANDARD 21046
First edition
2018-11
Silk — Test method for determining
the size of silk yarns
Soie — Méthode d'essai pour déterminer le titre des fils de soie
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
6 Atmosphere for conditioning and testing . 3
7 Procedure. 3
7.1 Sampling . 3
7.1.1 Sample length . 3
7.1.2 Sample quantity . 3
7.2 Preparation . 3
7.3 Weighing . 3
7.4 Data control . 4
7.5 Conditioned size . 4
8 Calculations. 4
8.1 General . 4
8.2 Average size . 5
8.3 Size deviation . 5
8.4 Maximum size deviation . 5
8.5 Conditioned size . 5
8.6 CV .
size 6
9 Test report . 6
Annex A (informative) Determination of drying time . 7
Annex B (informative) Tolerance between conditioned size and average size .8
Annex C (informative) Example of size test results for silk yarn . 9
Bibliography .11
Foreword
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This document was prepared by Technical Committee ISO/TC 38, Textiles, Subcommittee SC 23, Fibres
and yarns.
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iv © ISO 2018 – All rights reserved

Introduction
Silk yarns are made of natural silk fibres, including raw silk, tussah silk, dupion silk, thrown silk, etc.
Due to the intrinsic unevenness of the property of silk fibres and its manufacturing technique differing
from yarns made of staple fibres, the size (linear density) deviation of the silk yarns, such as raw silk
reeled from cocoon baves, is much bigger than that of the conventional yarns covered by ISO 2060.
Therefore, when measuring the size of silk yarns, the sample quantity, sample length, test device,
drying temperature, test items, calculation method of the results and tolerance for weighing errors are
all different from that for the conventional yarns. These special requirements are not prescribed in
ISO 2060. This document covers special size test regulations for silk yarns which are not covered by
ISO 2060.
INTERNATIONAL STANDARD ISO 21046:2018(E)
Silk — Test method for determining the size of silk yarns
1 Scope
This document specifies the test method for determining the size of silk yarns in all types of
package forms.
It is applicable to various kinds of silk yarns.
It is not applicable to spun silk yarns.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 139, Textiles — Standard atmospheres for conditioning and testing
ISO 6741-1:1989, Textiles — Fibres and yarns — Determination of commercial mass of consignments —
Part 1: Mass determination and calculations
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
silk yarn
yarn made of nature silk fibres, including raw silk, tussah silk, dupion silk, thrown silk
3.2
thrown silk
silk that has been twisted or doubled and twisted
3.3
size
linear density (mass per unit length) of silk yarns
Note 1 to entry: Size expresses the degree of coarseness or fineness of silk yarns.
Note 2 to entry: Size is expressed in dtex. It may also be expressed in deniers (den), for which the conversion from
[1]
dtex, as given in ISO 1144 , is 1 den = 0,9 dtex.
3.4
nominal size
size indicated by the manufacturer
3.5
average size
average value of the tested size of the sizing skeins
3.6
conditioned size
size calculated by adding the commercial moisture regain weight to the oven-dry weight
Note 1 to entry: For silk, the commercial moisture regain is 11,0 %, which was developed in 1841, and then was
widely used by Japan, China, India, etc. See Reference [4].
3.7
size deviation
standard deviation of the value of the tested size of the silk samples indicating the deviation degree of
the sizing skeins from the average size of the whole lot
3.8
maximum size deviation
indication of the deviation degree of the finest sizing skeins or the coarsest sizing skeins from the
average size of the whole lot
3.9
coefficient of variation of size
CV
size
percentage ratio between the size deviation and the average size
4 Principle
Under standard atmosphere, the sizing skeins are prepared by winding prescribed revolutions of silk
yarn on a reel with a specified length of circumference from conditioned silk samples. The sizing skeins
are weighed. The silk size is calculated from the length and mass, expressed in dtex (or den).
5 Apparatus
5.1 Wrap reel, with a reel circumference of (1 125 ± 2,5) mm, revolving at a constant speed of
(300 ± 15) r/min to ensure a constant tension or fitted with a positive feed system at a controlled tension
of (0,05 ± 0,01) cN/dtex, equipped with a dial showing the number of revolutions and an automatic stop-
motion to stop the reel.
A reel circumference of (1 000 ± 2,5) mm may be used and reported in the test report (see Clause 9) if
mutually agreed by the interested parties.
5.2 Size testing devices.
a) For balance: resolution ≤0,001 g.
b) For size tester: resolution ≤0,25 dtex (0,25 den).
5.3 Principle of size testing device.
The size testing device is a kind of balance with a built-in computing program which changes the weight
of each sizing skein (test sample of a prescribed length) into size value according to the definition of
size. The built-in program in the device can calculate and print out size distribution, size deviation,
maximum size deviation and CV automatically.
size
[2]
5.4 Oven, as described in ISO 2060 , in which the silk yarn samples are exposed at a temperature of
140 °C ± 2 °C.
2 © ISO 2018 – All rights reserved

6 Atmosphere for conditioning and testing
Atmospheres used for pre-conditioning, conditioning and testing shall be in accordance with ISO 139.
Condition the entire samples for a minimum of 12 h prior to testing and keep them conditioned during
testing.
7 Procedure
7.1 Sampling
7.1.1 Sample length
The test length of each sizing skein shall be 112,5 m obtained from 100 revolutions of the wrap reel.
When the reel circumference of (1 000 ± 2,5) mm is used, the number of revolut
...