In order to test two fabrics to see which is the better, it is necessary to rub the fabric or yarn on white unstarched cotton fabric.
In comparing the fastness of color of two fabrics it is necessary to have the rubbing equal in all cases.
_Questions_
1. What is meant by friction?
2. What is meant by the expression "fastness of color of two fabrics"?
3. How may the fastness of a colored material be tested to withstand friction?
=Experiment 39--Test of Fastness of Color against Rain=
Apparatus: Water, undyed yarn.
Materials: Silk and woolen fabrics.
Reference: _Textiles_, page 243.
_Directions_
Silk and woolen materials for umbrella making, raincoats, etc., are expected to be rainproof. These fabrics are tested by plaiting with undyed yarns and left to stand all night in water. Notice whether the color of the fabric has run into the undyed yarns.
Take a sample of the fabric and shake some drops of water on it.
Notice whether it loses its luster when the drops have dried. Spotting may be prevented by placing a damp cloth on the wrong side of the material; roll the two together, and when evenly damp, unroll and press through the damp cloth with a fairly hot iron.
Place a piece of the fabric in the sun so that the sun and rain may come in contact with it. Notice whether it loses its color and becomes gray and dull.
=Experiment 40--Test of Fastness of Color in Sunlight=
Apparatus: Cardboard.
Materials: Silk, woolen, and cotton fabrics.
Reference: _Textiles_, page 244.
_Directions_
Cover one end of the sample of cloth with a piece of cardboard. Expose the fabric to the sunlight for a number of days and examine the cloth each day and notice whether the part exposed has changed in color when compared with the part covered. Count the number of days it has taken the sunlight to change the color. Does direct sunlight have any effect upon colored fabrics? Which is the most affected by the sun, silk, woolen, or cotton fabrics, dyed with same dyestuff, in the same length of time? Are fabrics changed any sooner by the sun than by the weather?
=Experiment 41--Test of Fastness of Color to Weather, Light, and Air=
Materials: Cotton, silk, and woolen fabrics.
Reference: _Textiles_, page 244.
_Directions_
Examine various fabrics for fastness to weather, light, and air by placing samples outside of a window so that they will be exposed to the weather, light, and air. Have duplicate samples of the above away from the weather and light. Compare the samples exposed to the weather with those in the house and note the number of days it takes to change. Classify the fabrics. Which of the fabrics are most easily affected by the weather, light, and air?
=Experiment 42--Test of Fastness of Color against Street Mud and Dust=
Apparatus: Porcelain dish, lime, and water.
Materials: Cotton, silk, and woolen fabrics.
Reference: _Textiles_, page 243.
Ladies' dress goods are expected to withstand the action of mud and dust. In order to test a fabric for the resistance, the sample should be moistened with lime and water (10 per cent solution), dried, and brushed. Or sprinkle with a 10 per cent solution of soda, drying, brushing, and noting any change in the color.
_a._ Is there any change in color after the lime water has been removed from the cloth?
_b._ With what may the action of the lime water or soda be compared?
=Experiment 43--Testing Rubberized Fabrics=
Materials: Rubberized fabrics.
A great many rubberized fabrics are used for hospitals, domestic purposes and for clothing. On account of the high price of excellent rubberized fabrics a great many substitutes are placed on the market that are satisfactory to the eye, but have not the wearing qualities for the service they are intended to render.
Strength and Resistance to Scratching.--In order to test a rubberized fabric to see if it has the necessary strength to stand everyday use, see if it is possible to scratch it with the finger nail. Then crease it and crumple it between the hands. Then spread it out very carefully and notice whether there are any broken places. If there are it should be rejected.
Waterproof Qualities.--A rubberized fabric should be waterproof. A sample may be tested by forming a bag with it and filling it with water. Crumple the bag while it is filled with water. Notice whether it cracks or leaks.
Examine various rubberized fabrics and notice whether they are substantial.
=Experiment 44--Test for Vegetable and Animal Fiber=
Apparatus: Acid, fire.
Materials: Warp and filling threads of cotton and woolen fabrics.
Reference: _Textiles_, page 239.
_Directions_
One of the most useful tests is to see whether an article is made of wool, cotton, or silk, and if a composition of two or more materials, to estimate the percentage of each. Practical experience can teach one much in this respect, and in many cases inspection is quite insufficient. A more reliable test is to burn a piece of material and notice how it burns.
Take a sample of a woolen and cotton fabric; separate the warp and filling and untwist one piece of warp and one piece of filling yarn.
Burn a piece of untwisted yarn and notice whether it burns slowly and curls up into a black crisp cinder leaving a disagreeable smell, or burns with a flash leaving a light ash behind.
_Questions_
1. Describe the burning process.
2. What is the burning test for vegetable fiber?