Next to food and shelter, clothing is the most important need to humans, as it comes into use initially as a means of protection against the actions of weather. In modern trends, its utility for enhancing the appearance of an individual could be considered equally important. Also, some types of fabrics are used for different type types of industrial purposes. In order to judge the suitability of a fabric for different end uses such as clothing, industrial applications, etc., it should have certain desirable properties. Hence the testing of fabric for quality is important and essential in the interest of the consumer.
Fabrics are tested for the following quality particulars:
Dimensional Characteristics |
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Threads Per inch |
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Count |
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Weight of fabric |
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Crimp |
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Strength |
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Abrasion resistance |
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Handle |
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Fabric Dimensional Properties:
Under these properties, we consider Length of fabric, Width of fabric, and Thickness of fabric.
Fabric Length:
Fabric length is defined as the distance between two ends of fabric along the selvedge. Fabric length measurement is carried out by the following methods:
By use of measuring table.
By use of measuring scale/Tape.
By use of measuring machine (eg: Trumeter).
Fabric width:
The width of the fabrics is also measured after conditioning them in the standard testing atmosphere, in a relaxed stage. For the determination of width, two alternative procedures are prescribed in the various standard specifications. In one method, measurement is made after conditioning the fabric in the standard testing atmosphere in a relaxed state. In another method, measurement is made in the prevailing atmosphere and a correction is applied to it based on the determination made on a test piece conditioned in the standard atmosphere. The accuracy with which the determinations are to be made and reported is dependent on the width of the fabric and in the Indian standard method, a uniform accuracy of 5mm is prescribed. Also, it is recommended to make five measurements at the points evenly spaced along the length of the fabric. But as per British Standards, ten meters should be made at points distributed at roughly equal distances throughout the full length of the piece. Where the full length is not available, a sample length of not less than one yard should be used and its width measured at three places. Then the mean width and the range in width should be reported.
Measurement of Width:
Fabric width is the distance from the outside of one selvedge to the outside of the other, measured perpendicular to the length of the fabric.
The cloth is laid on a smooth flat measuring table without applying more tension. The tension applied must be just sufficient to keep the fabric straight and flat. Then a measuring scale is placed at right angles to the selvages, the width of the fabric is measured correct to 1mm. The width is measured at five different places and the average is calculated and rounds off the mean value as follows:
To nearest 1mm for width up to 50cm inclusive.
To nearest 5mm for width up to 100cm inclusive.
To nearest 10mm for width over 100cm.
In the case of fabrics, including narrow-width fabrics with irregular selvedge, at least two readings should be taken.
For continuous measurement of width, an apparatus is used which is based upon a pair of photo-electric cells. They are placed on each selvedge and scan the edges of the fabrics and detect the changes in width. The signals are then translated into fabric width and indicated on a meter or recorded on a chart. In this case, an accuracy of + or – 0.3cm is claimed.
Note:
If wavy selvedge is present due to weft variation or weave effects, maximum and minimum widths should be recorded and the wavy selvedge reported.
If full width of the fabric is required the overall width including selvedges is measured. If the width within lists (width of the body) is required, the width between the innermost selvedge threads is measured.
Where only samples are measured, the width is measured in an unconditioned state and corrected from the measured changes in the width of the samples.
Fabric Thickness:
It is defined as the distance between two fabric surfaces under specific applied pressure.
For measuring the thickness of a wire or a plate, calipers or micrometers are used. but the use of these things for the measurement of the thickness of the fabric is not possible, since fabrics are liable to compress during the measuring. Therefore the measurement of fabric thickness demands accuracy.
Principle of the measurement of fabric Thickness:
The fabric is kept between two plane-parallel plates and a known arbitrary is applied between the plates and maintained. Then the distance between the plates is measured precisely.
The following points need consideration in fabric thickness measurement:
Shape and Size of pressure foot: Normally circular foot of dia 3/8 inch is used. The ratio between the foot diameter to the cloth thickness should not be less than 5:1.
Shape and Size of the anvil: If the anvil is of circular type its diameter should be at least 2 inches greater than the pressure foot. when the sample is greater than the anvil, a smooth plane board may conveniently surround the anvil for suitable support for the cloth.
Applied pressure: Suitable weights may be added to the presser foot and preferred pressure may be applied.
The velocity of presser foot: The presser foot should be lowered onto the sample very slowly (at a rate of 2/1000 inches per sec.) and carefully.
Time: The Thickness is read from the dial of the instrument only when the pointer ceased vibrations and not earlier.
Indication of thickness: Usually a clock-type dial gauge is built into the thickness tester. it should be rigidly mounted in a suitable frame. after setting the dial to zero, the instrument must be capable of measuring to an accuracy of 1% for fabric over 0.1 mm in thickness and to 0.001 mm for fabrics that are not exceeding 0.1mm in thickness.
Method of measuring Thickness:
The presser foot and avil are cleaned with clean paper.
If required, weights are added to the presser foot and the gauge is set to read zero.
No specimen preparation is required. But selvedges and the creased areas should be avoided.
If possible, the cloth may be conditioned for about 24 hours in a standard atmosphere.
At least, thickness is measured at 5 places and the mean value is reported.
In the test report, details of the pressure, size of the presser foot, and the time should be given.
In the study of fabric geometry, fabric thickness is mainly used for checking the conformity to the specifications, in the study of fabric properties such as thermal insulation, resilience, dimensional stability, fabric stiffness, abrasion, etc...
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