GB/T 4668-1995 English PDF (GB/T4668-1995)

GB/T 4668-1995: Textiles - Woven fabrics - Determination of number of threads per unit length
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GB/T 4668-1995
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 59.080.30
W 04
Replacing GB 4668-84 and GB 8678-88
Textiles - Woven Fabrics - Determination of
Number of Threads per Unit Length
ISSUED ON. DECEMBER 08, 1995
IMPLEMENTED ON. MAY 01, 1996
Issued by. State Bureau of Technical Supervision
Table of Contents
1 Subject Content and Application Scope ... 3 
2 Normative References ... 3 
3 Definitions ... 3 
4 Principle ... 4 
5 Minimum Measuring Distance ... 4 
6 Conditioning and Testing Atmosphere ... 4 
7 Test Specimen ... 5 
8 Method A - Dissection of Fabric ... 5 
9 Method B - Counting Glass ... 5 
10 Method C - Traversing Thread Counter ... 6 
11 Calculation and Expression of Results ... 7 
12 Test Report ... 7 
Annex A Method for the Determination of the Number of Threads Using
Gratings and Optoelectronic Scanner (Informative) ... 8 
Additional Explanation ... 11 
Textiles-Woven Fabrics-Determination of Number of
Threads per Unit Length
This standard is based on the international standard ISO 7211/2-1984 "Textiles -
Woven Fabrics – Construction - Methods of Analysis - Part 2. Determination of
Number of Threads per Unit Length".
1 Subject Content and Application Scope
This standard specifies three methods for the determination of number of threads per
unit length in woven fabrics. Any of the three methods may be used, the choice
depending on the character of the fabric. However, in case of dispute method A is
recommended.
This standard is applicable to the determination of number of threads per unit length in
various woven fabrics.
Method A. Dissection of fabric, suitable for all fabrics, in particular, complicated
weaves.
Method B. Counting glass, suitable for fabrics with more than 50 threads per
centimetre.
Method C. Traversing thread counter, suitable for all woven fabrics.
Note. Three methods using parallel line gratings, tapered line gratings and optoelectronic scanning density meter for
the determination of number of threads per unit length in woven fabrics have been given in Annex A (Informative) for
information. These methods have low measurement accuracy and limitation but can be used to give rapid and rough
estimates.
2 Normative References
GB 6529 Textiles - Standard Atmospheres for Conditioning and Testing
3 Definitions
3.1 Number of threads per unit length. warp number and weft number per unit length
in woven fabrics under no wrinkle or tension, generally expressed with root/10cm.
3.2 Number of threads in warp direction. number of warp threads per unit length in
specified in GB 6529, and arbitration test shall adopt Grade 2 standard atmosphere.
Routine inspection may be carried out in general atmosphere.
7 Test Specimen
The specimens shall be flat and smooth and free from wrinkle and obvious skew.
No specially prepared specimens are required except for method A, but determine the
threads at not less than five different points selected to represent the fabric as fully as
possible. Expose the fabric or specimens to the atmosphere for testing for at least 16h
before making the test.
8 Method A - Dissection of Fabric
8.1 Apparatus
a. Steel ruler. with a length of 5~15cm and with millimetre scale on the ruler
surface;
b. Dissecting needle;
c. Scissors.
8.2 Procedure
8.2.1 Take test specimens slightly larger than the minimum measuring distance at
proper position of the specimen after conditioning.
8.2.2 Remove partial thread from the specimen edge, and measure with a steel ruler
to make the specimen reach the specified minimum measuring distance 2cm, with an
allowable tolerance of 0.5 thread.
8.2.3 Remove above-mentioned prepared specimens one by one from the edge; to
be convenient for counting, arrange the threads into a group with 10 roots, then obtain
the number of threads in fabrics in warp (weft) direction within a certain length.
8.2.4 If the warp and weft densities are determined simultaneously, take a
rectangular specimen to make the lengths of warp and weft directions meet the
minimum measuring distance. Remove the specimens, then obtain the number of
warp threads and weft threads within a certain length.
9 Method B - Counting Glass
9.1 Apparatus
Annex A
Method for the Determination of the Number of Threads Using
Gratings and Optoelectronic Scanner
(Informative)
A1 Method D-Parallel line grating
This method is suitable only for fabrics where thread patterns yield interference bands
that are readily visible.
A1.1 Principle
The number of threads is determined through observing the interference bands
produced when the parallel line grating is placed on the fabric.
A1.2 Apparatus
Parallel line grating, divided into several grades according to different specifications.
A1.3 Determination method
Place the grating selected as most suitable on the fabric with its lines parallel to the
threads of the tested system. If a suitable grating has been chosen, a number of
bands parallel to the edge of the grating will be seen. Count the number of threads
according to the following rules.
A1.3.1 If, when the grating and tested fabric are rotated with a small angles, the
transverse bands appear (vertical to grating line), the number of threads in tested
fabric is equal to the grating mark number.
A1.3.2 If, when the grating is rotated slightly, the bands appear to rotate in the same
direction as the grating, the number of threads per unit length in tested fabric is equal
to the grating mark number minus the number of bands.
A1.3.3 If, when the grating is rotated slightly, the bands appear to rotate in the
opposite direction as the grating, the number of threads per unit length in tested fabric
is equal to the grating mark number plus the number of bands.
A1.4 The calculation and expression of results and the test report are in accordance
with the content of Chapter 11 and Chapter 12 of this standard.
A2 Method E-Taper line grating
This method is suitable only for fabrics where thread patterns yield interference bands
that are readily visible.
A2.1 Principle
The number of threads is determined through observing the interference bands
produced when the taper line grating is placed on the fabric.
A2.2 Apparatus
Taper line grating, divided into several grades according to different specifications.
A2.3 Determination method
Lay the fabric flat, place the grating selected as most suitable on the fabric with its
long side parallel to the tested threads. Curvilinear pattern approximate to symmetry
will appear at this time, and the scale reading to which the two short arms of this cross
point give the threads per centimetre in fabric.
A2.4 The calculation and expression of results and the test report are in accordance
with the content of Chapter 11 and Chapter 12 of this standard.
A3 Method F-Optoelectronic scanning
This method is applicable to the determination of the number of threads per unit
length in various plain and twill fabrics.
A3.1 Principle
Make incident light emit to fabric specimen through a condenser, reflected light of
warp threads or weft threads in fabric forms one-way grating band image through
optical system, convert this image to electric impulse signal through optoelectronic
scanning, amplify and shape, and then drive a nixie tube through a counting system to
directly indicate the number of warp (weft) threads in fabric within 5cm length.
A3.2 Apparatus
Optoelectronic scanning thread counter, with a minimum measuring distance of 5cm.
A3.3 Determination method
A3.3.1 Power on, open the power supply switch of the host, then the nixie tube and
light source lamp will light.
A3.3.2 Place a piece of white paper below the apparatus, and regulate the output
voltage to about 4.5V.
A3.3.3 Selecting measurement grade
Additional Explanation
This standard was proposed by the Department of Science and Technology
Development of China Textile Association.
This standard shall be under the jurisdiction of the Standardization Research Institute
of China Textile Association.
Standardization Research Institute of China Textile Association AND Shanghai Textile
Standard Measurement Institute are responsible for drafting this standard.
Chief drafting staffs of this standard. Zheng Yuying, He Jieren.
This standard was established in 1988 and revised in 1995.
GB/T 4668-1995
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 59.080.30
W 04
Replacing GB 4668-84 and GB 8678-88
Textiles - Woven Fabrics - Determination of
Number of Threads per Unit Length
ISSUED ON. DECEMBER 08, 1995
IMPLEMENTED ON. MAY 01, 1996
Issued by. State Bureau of Technical Supervision
Table of Contents
1 Subject Content and Application Scope ... 3 
2 Normative References ... 3 
3 Definitions ... 3 
4 Principle ... 4 
5 Minimum Measuring Distance ... 4 
6 Conditioning and Testing Atmosphere ... 4 
7 Test Specimen ... 5 
8 Method A - Dissection of Fabric ... 5 
9 Method B - Counting Glass ... 5 
10 Method C - Traversing Thread Counter ... 6 
11 Calculation and Expression of Results ... 7 
12 Test Report ... 7 
Annex A Method for the Determination of the Number of Threads Using
Gratings and Optoelectronic Scanner (Informative) ... 8 
Additional Explanation ... 11 
Textiles-Woven Fabrics-Determination of Number of
Threads per Unit Length
This standard is based on the international standard ISO 7211/2-1984 "Textiles -
Woven Fabrics – Construction - Methods of Analysis - Part 2. Determination of
Number of Threads per Unit Length".
1 Subject Content and Application Scope
This standard specifies three methods for the determination of number of threads per
unit length in woven fabrics. Any of the three methods may be used, the choice
depending on the character of the fabric. However, in case of dispute method A is
recommended.
This standard is applicable to the determination of number of threads per unit length in
various woven fabrics.
Method A. Dissection of fabric, suitable for all fabrics, in particular, complicated
weaves.
Method B. Counting glass, suitable for fabrics with more than 50 threads per
centimetre.
Method C. Traversing thread counter, suitable for all woven fabrics.
Note. Three methods using parallel line gratings, tapered line gratings and optoelectronic scanning density meter for
the determination of number of threads per unit length in woven fabrics have been given in Annex A (Informative) for
information. These methods have low measurement accuracy and limitation but can be used to give rapid and rough
estimates.
2 Normative References
GB 6529 Textiles - Standard Atmospheres for Conditioning and Testing
3 Definitions
3.1 Number of threads per unit length. warp number and weft number per unit length
in woven fabrics under no wrinkle or tension, generally expressed with root/10cm.
3.2 Number of threads in warp direction. number of warp threads per unit length in
specified in GB 6529, and arbitration test shall adopt Grade 2 standard atmosphere.
Routine inspection may be carried out in general atmosphere.
7 Test Specimen
The specimens shall be flat and smooth and free from wrinkle and obvious skew.
No specially prepared specimens are required except for method A, but determine the
threads at not less than five different points selected to represent the fabric as fully as
possible. Expose the fabric or specimens to the atmosphere for testing for at least 16h
before making the test.
8 Method A - Dissection of Fabric
8.1 Apparatus
a. Steel ruler. with a length of 5~15cm and with millimetre scale on the ruler
surface;
b. Dissecting needle;
c. Scissors.
8.2 Procedure
8.2.1 Take test specimens slightly larger than the minimum measuring distance at
proper position of the specimen after conditioning.
8.2.2 Remove partial thread from the specimen edge, and measure with a steel ruler
to make the specimen reach the specified minimum measuring distance 2cm, with an
allowable tolerance of 0.5 thread.
8.2.3 Remove above-mentioned prepared specimens one by one from the edge; to
be convenient for counting, arrange the threads into a group with 10 roots, then obtain
the number of threads in fabrics in warp (weft) direction within a certain length.
8.2.4 If the warp and weft densities are determined simultaneously, take a
rectangular specimen to make the lengths of warp and weft directions meet the
minimum measuring distance. Remove the specimens, then obtain the number of
warp threads and weft threads within a certain length.
9 Method B - Counting Glass
9.1 Apparatus
Annex A
Method for the Determination of the Number of Threads Using
Gratings and Optoelectronic Scanner
(Informative)
A1 Method D-Parallel line grating
This method is suitable only for fabrics where thread patterns yield interference bands
that are readily visible.
A1.1 Principle
The number of threads is determined through observing the interference bands
produced when the parallel line grating is placed on the fabric.
A1.2 Apparatus
Parallel line grating, divided into several grades according to different specifications.
A1.3 Determination method
Place the grating selected as most suitable on the fabric with its lines parallel to the
threads of the tested system. If a suitable grating has been chosen, a number of
bands parallel to the edge of the grating will be seen. Count the number of threads
according to the following rules.
A1.3.1 If, when the grating and tested fabric are rotated with a small angles, the
transverse bands appear (vertical to grating line), the number of threads in tested
fabric is equal to the grating mark number.
A1.3.2 If, when the grating is rotated slightly, the bands appear to rotate in the same
direction as the grating, the number of threads per unit length in tested fabric is equal
to the grating mark number minus the number of bands.
A1.3.3 If, when the grating is rota...