Textiles Part 36

=Experiment 33--Determining the Direction of Warp and Filling=

Apparatus: Microscope.

Materials: Silk, cotton, and woolen fabrics.

Reference: _Textiles_, page 238.

When one examines a fabric the first thing to do is to determine the direction of the warp and direction of the filling.

Fabrics with Selvedge.--Examine any fabric with a selvedge and notice that the warp threads run in the same direction as the length (longest side) of the selvedge. What direction will the filling threads bear to the selvedge?

Fabrics with a Nap.--Examine a piece of flannel and notice the direction of the nap. Why will the direction of the nap be the same as the direction of the warp? Remember the way in which the fabric enters the napping machine.

Fabrics Containing Double Threads.--Examine a fabric containing double and single threads and notice that the warp contains the double threads. Why?

Fabrics Containing Cotton and Woolen Yarn.--Examine a fabric containing cotton and woolen threads running in different directions and notice that the cotton threads form the warp. Why?

Another way to tell the warp threads in a fabric is to examine warp and filling threads very closely and notice which set contains the greater twist? Why? See if they are separated at more regular intervals. Why?

Stiffened or Starched Fabrics.--Examine stiffened or starched goods very closely and notice the threads. If only one set can be seen they are the warp threads. The stiffer and straighter threads are found in the warp. Why? The rough and crooked threads are seen in the filling.

=Experiment 34--Determining the Density of a Fabric=

Apparatus: Pick gla.s.s.

Materials: Samples of cloth.

Reference: _Textiles_, page 238.

_Directions_

1. Examine different samples of cloth and determine the number of filling threads and warp threads by means of a pick gla.s.s.

2. Then examine different priced fabrics of the same kind and see whether the low or high priced fabric has the greater density.

=Experiment 35--Determining Weight=

Apparatus: Balances, die.

Materials: 4 square inches of cloth.

Reference: _Textiles_, page 239.

_Directions_

1. Fabrics are bought and sold by the yard. In order to express the amount of wool or cotton in a fabric the weight in ounces per yard is usually given.

2. In order to find the number of ounces per yard a piece of cloth of definite size, usually about 4 sq. in., is stamped out by means of a die, or cut by means of a tin plate exactly 4 sq. in. (2 in. on the side). This is then weighed on very accurate balances and expressed in grains. Find the weight per yard. Remember 7000 grains equal 1 lb.; 16 oz. equal 1 lb.

=Experiment 36--Determining Shrinkage=

Apparatus: Hot water.

Material: Sample of woolen fabric.

Reference: _Textiles_, page 239.

_Directions_

1. Take a sample of a woolen fabric 12 in. by 20 in. and pour hot water over it and leave it immersed over night. Then dry it in the morning at a moderate temperature without stretching. Then measure its length and divide the difference in lengths by the original length.

The quotient multiplied by 100 will give the per cent of shrinkage.

2. Repeat the same experiment with a worsted fabric, and with a cotton fabric.

3. Why does the woolen fabric shrink more than the worsted?

=Experiment 37--Test of Fastness[28] of Color under Was.h.i.+ng=

Apparatus: Porcelain dish, soap solution. Materials: Cotton and woolen fabrics. Reference: _Textiles_, page 242.

_Directions_

1. Colored goods and printed fabrics should withstand the action of was.h.i.+ng. They require more care than white goods and should be soaked in cold water containing very little soap and no soda. They should be dried in the shade as a very hot sun will fade them. If it is necessary to dry them in the sun be sure that they are dried wrong side out, as direct sunlight fades them about five times as much as reflected light.

2. All colored fabrics should stand mechanical friction as well as the action of soap liquor and the temperature of the was.h.i.+ng operation. In order to test the fabric for fastness a piece should be placed in a soap solution similar to that used in the ordinary household, and heated to 131 F. The treatment should be repeated several times.

3. If the color fails to run it is fast to was.h.i.+ng.

_Questions_

1. Why should more care be exercised in was.h.i.+ng colored goods than white?

2. How may colored fabrics be tested to show that they stand the action of soap solution?

3. Does a moderately warm temperature (131 F.) affect the fastness of colored fabric?

=Experiment 38--Test of Fastness of Color under Friction=

Apparatus: Yarn, white unstarched cotton fabric.

Materials: Fabrics worn near the skin.

Reference: _Textiles_, page 242.

_Directions_

Stockings, hosiery yarns, corset stuffs, and all fabrics intended to be worn next to the skin must be closely knitted to withstand friction and must not rub off, stain, or run, that is, the dyed materials must not give off their color when worn next to the human epidermis (skin), or in close contact with other articles of clothing, as in the case of underwear.