Fastness Under Friction. Stockings, hosiery yarns, corset stuffs, and all fabrics intended to be worn next to the skin must be permanent under 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 colored articles of clothing, as in the case of underwear.
The simplest test is to rub the fabric or yarn on white unstarched cotton fabric. In comparing the fastness of two fabrics it is necessary to have the rubbing equal in all cases.
Resistance to Perspiration. With fabrics coming in contact with the human skin it is necessary in addition to fastness under friction that they should withstand the excretions of the body. The acids of perspiration (acetic, formic, and butyric) often become so concentrated that they act on the fiber of the fabric.
In order to test the fabric for resistance, place the sample in a bath of 30 per cent dilute acetic acid (one teaspoonful to a quart of water) warmed to the temperature of the body, 98.6 degrees F. The sample should be dipped a number of times, and then dried without rinsing between parchment paper.
Fastness against Rain. 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 cold water.
Resistance to Street Mud and Dust. Ladies’ dress goods are expected to withstand the action of mud and dust. In order to test a fabric for this 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 changes in color.
Fastness to Weather, Light, and Air. Various people have attempted to set up standard degrees of fastness—for every shade of color is affected by the action of sun, light, and air—and as a result fabrics that remain without appreciable alteration for a month of exposure to direct summer sunlight are classified as “fast,” and those undergoing slight appreciable change under the same conditions as “fairly fast.” “Moderately fast” colors are those altering considerably in fourteen days; and those more or less completely faded in the same time (fourteen days) are designated as “fleeting.”
Directions for testing fastness of Color in Sunlight. 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 in the dark 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.
Brown in woolen materials is likely to fade. Brown holds its color in all gingham materials.
Dark blue is an excellent color for woolens and ginghams. Light blues on the other hand usually change.