5. A very simple way for telling the amount of loading or weighting in a cotton fabric is to weigh a given sample, then “boil the fabric out in hot water,”—boiling for several hours and then drying it. The difference in weight after drying and before boiling gives the weight of sizing material per sample piece.
6. If mineral loading has been used to a great extent, a large residue is left after burning.
Experiment 52—Testing the Strength of Cloth
Apparatus: Dynamometer.
Materials: Various fabrics.
Reference: Textiles, page [237].
Directions
1. An excellent way to test the strength of a fabric is to place the two thumbs together and press them down on the sample, holding it tight underneath. Then try to break the threads, first in one direction and then in the other. Do they break easily? Notice whether one set is very much stronger than the other.
2. Manufacturers usually test yarn and fabrics by means of an instrument called a dynamometer. In this way one can find out whether a yarn or fabric comes up to the necessary strength, and whether it has the required yield or stretch. Both these points are of importance in practical work, for it is essential that the yarn as shown should at least be strong enough to bear the strain of manufacture. The test is made by stretching a hank of yarn between the two hooks of a cloth testing machine. The handle at the side is now turned, so that the lower hook descends and puts a strain on the hank. This strain is increased, and at the same time the pointer moves around the dial, which indicates in pounds the amount of strain. When the threads of the hank begin to break, the strain is released, and the catch at the side keeps the pointer in position until the amount of strain is read on the dial. The distance stretched by the yarn before breakage occurs is shown in inches and fractions of an inch, in the small indicator arranged near the upper hook.
Test different fabrics and yarns.
Experiment 53—Characteristics of a Knitted Fabric
Apparatus: Pick glass.
Materials: Knitted fabric, woven fabric.
Reference: Textiles, page [153].