WEBVTT 00:00:00.010 --> 00:00:05.139 >> Skewness, or torque, is the annoying characteristic of some fabrics and 00:00:05.149 --> 00:00:10.990 garments to twist after laundering. As a result of skewing, side seams, sleeves, 00:00:11.009 --> 00:00:14.849 legs, and other parts of a garment will become displaced, leading to an 00:00:14.869 --> 00:00:22.169 unsatisfactory appearance. "AATCC Test Method 179: -- Skewness Change in Fabric 00:00:22.189 --> 00:00:27.119 and Garment Twist Resulting from Automatic Home Laundering." This test method 00:00:27.139 --> 00:00:31.640 determines change in skewness in woven and knitted fabrics, or twist in 00:00:31.660 --> 00:00:36.019 garments, when subjected to repeated automatic laundering procedures commonly 00:00:36.039 --> 00:00:40.919 used in the home. Washing and drying procedures used for shrinkage tests, and 00:00:40.939 --> 00:00:45.859 other home laundering tests, are specified for this method. For some fabrics, 00:00:45.879 --> 00:00:50.039 the degree of twist in the garments is not solely depended on its behavior in 00:00:50.059 --> 00:00:55.179 the unsewn state. It also may be dependent on the manner of garment assembly. 00:00:55.199 --> 00:00:59.879 Notice that one pant leg on this garment has skew and the other does not. 00:00:59.899 --> 00:01:04.500 Garment twist is defined as a rotation, usually lateral, between different 00:01:04.519 --> 00:01:08.739 panels of a garment, resulting from the release of latent stresses of the woven 00:01:08.759 --> 00:01:13.019 or knitted fabric forming the garment, that build up in manufacturing during 00:01:13.039 --> 00:01:19.320 laundering. Twist may also be referred to as torque or spirality. Skewness is 00:01:19.340 --> 00:01:23.680 defined as a fabric condition resulting when filling yarns or knitted courses 00:01:23.700 --> 00:01:28.219 are angularly displaced from a line perpendicular to the edge or side of the 00:01:28.239 --> 00:01:38.849 fabric. Change in skewness in fabric, or twist in garment, is measured using 00:01:38.869 --> 00:01:43.670 benchmarks applied to the specimens before laundering. The displacement measured 00:01:43.689 --> 00:02:13.689 from the original marks is the basis for determining skewness. Two test methods 00:02:14.989 --> 00:02:19.609 are used for determining skewness. The first method makes use of a square that 00:02:19.629 --> 00:02:23.909 is drawn on the fabric or garment prior to laundering. After laundering the 00:02:23.930 --> 00:02:32.839 distortion of the square is measured. The other method makes use of lines that 00:02:32.859 --> 00:02:36.839 intersect at a right angle. After laundering, the displacement of the 00:02:36.859 --> 00:02:42.539 intersecting lines is expressed in percentage skew. Three specimens are tested 00:02:42.560 --> 00:02:47.489 for each sample, to increase the precision of the average. When testing fabrics, 00:02:47.509 --> 00:02:52.089 where possible, cut specimens from different areas of the fabric so that each 00:02:52.109 --> 00:02:56.759 specimen will contain different groups of lengthwise and widthwise yarns. 00:02:56.780 --> 00:03:02.679 Identify the fabric face. Mark the lengthwise direction on each specimen. 00:03:02.699 --> 00:03:07.599 Whenever dimensional change, appearance, and skewness measurements are required 00:03:07.620 --> 00:03:13.239 for fabrics, the specimen dimensions can be the same for that used in "AATCC 00:03:13.259 --> 00:03:18.869 Method 124: Smoothness Appearance of Fabrics After Repeated Home Laundering," or 00:03:18.889 --> 00:03:24.869 in "AATCC Method 135: Dimensional Changes of Fabrics After Home Laundering." In 00:03:24.889 --> 00:03:30.529 these cases, marking by skewness method one is used. Method one makes use of 00:03:30.549 --> 00:03:36.209 benchmarks placed on fabric swatches, or on large panels of a garment. Here, a 00:03:36.229 --> 00:03:41.549 knit fabric has a 15 by 15 inch square template placed with the vertical edges 00:03:41.569 --> 00:03:45.969 parallel to the edge of the fabric. The parameter of the template is marked to 00:03:45.989 --> 00:03:51.019 define the size of the specimen. Then the specimen is marked with 10 inch pairs 00:03:51.039 --> 00:03:55.779 of benchmarks parallel to the length of the specimen and two 10 inch pairs of 00:03:55.799 --> 00:04:00.699 benchmarks are marked perpendicular to the length of the specimen. Next, the 00:04:00.719 --> 00:04:05.959 benchmarks are labeled as A, B, C, and D in clockwise direction, starting with 00:04:05.979 --> 00:04:10.219 the lower left corner. A line is then drawn through each of the four sets of 00:04:10.239 --> 00:04:40.240 adjacent benchmarks so that a square is formed. Finally, the specimen is cut 00:05:23.529 --> 00:05:29.360 down to the 15 by 15 inch marks for laundering. When testing fabrics, test three 00:05:29.379 --> 00:05:34.910 specimens whenever possible. When testing garments using this method, test three 00:05:34.930 --> 00:05:39.509 garment specimens, or a total of three areas of two garments, to increase 00:05:39.529 --> 00:05:58.089 precision of the average. Use the largest panels in the garments. After 00:05:58.109 --> 00:06:06.230 laundering, follow the procedures found in AATCC Test Methods 124, 135, 143, and 00:06:06.250 --> 00:06:12.589 179 for preparation and condition prior to testing. After conditioning, lay each 00:06:12.609 --> 00:06:17.129 test specimen -- without tension -- on a flat, smooth, horizontal surface for a 00:06:17.149 --> 00:06:22.509 measurement. Method one, which uses a square with the corners marked A, B, C, 00:06:22.529 --> 00:06:27.810 and D, measures the sheer distortion of the square by analyzing the diagonals of 00:06:27.829 --> 00:06:33.120 the square. The analysis of the skewness square requires the measurements of the 00:06:33.139 --> 00:06:38.100 diagonal lines and a percent skewness calculation is made from those diagonal 00:06:38.120 --> 00:06:44.019 lengths. Diagonal line AC is measured in inches and recorded to the nearest one 00:06:44.039 --> 00:07:12.620 hundredth of an inch. The diagonal length for BD is also measured and recorded. 00:07:12.639 --> 00:07:17.199 As stated, method one calculates the percentage change in skewness of the 00:07:17.219 --> 00:07:22.759 displaced square. The lengths of the diagonal lines AC and BD are measured to 00:07:22.779 --> 00:07:28.480 the nearest tenth of an inch. In this option, the diagonals AC and BD are used 00:07:28.500 --> 00:07:34.050 in a formula that expresses sheer distortion of a plain. The value is expressed 00:07:34.069 --> 00:07:40.230 to the nearest 0.1 percent, as follows. The difference between the diagonals is 00:07:40.250 --> 00:07:45.870 multiplied by a factor of two and then divided by the sum of the diagonals. This 00:07:45.889 --> 00:07:51.230 number is multiplied by 100 to give the percentage of skewness. For example, if 00:07:51.250 --> 00:08:00.050 diagonal AC is 13.70 inches and BD is 13.65 inches, then the percent skewness 00:08:00.069 --> 00:08:09.589 would be 13.70 minus 13.65 times 2. And this product, divided by 13.70 plus 00:08:09.609 --> 00:08:16.319 13.65, and this value multiplied by 100, will give 3.7 percent skewness. A 00:08:16.339 --> 00:08:20.319 positive percent change indicates product skewness to the left, which is 00:08:20.339 --> 00:08:25.100 referred to as left-hand skew. A negative percent change indicates product 00:08:25.120 --> 00:08:29.909 skewness to the right, which is referred to as right hand skew. Marking method 00:08:29.929 --> 00:08:34.789 two uses different benchmarks as compared to method one for fabric specimens and 00:08:34.808 --> 00:08:39.950 garments. Using a suitable marking device, a horizontal reference line is drawn 00:08:39.970 --> 00:08:45.539 across the width of the specimen and is labeled YZ. Line YZ should be 00:08:45.559 --> 00:08:49.500 approximately three inches above the bottom edge of the fabric specimen, or the 00:08:49.519 --> 00:08:54.409 hem of the garment. If the bottom edge, or hem, is not straight, draw the 00:08:54.429 --> 00:09:00.169 reference line perpendicular to the vertical axis of symmetry of the specimen. 00:09:00.189 --> 00:09:05.769 Place a bench mark -- A -- perpendicular to, and midway, on line YZ. Place one 00:09:05.789 --> 00:09:10.850 leg of a right angle marking device along YZ so that the second leg is on a 00:09:10.870 --> 00:09:16.509 perpendicular upward from point A. At a distance of 20 inches up the right angle 00:09:16.529 --> 00:09:22.439 marking device, directly above point A, draw a benchmark parallel to line YZ. 00:09:22.459 --> 00:09:27.659 Draw a vertical benchmark starting at 19 inches from point A perpendicular to 00:09:27.679 --> 00:09:33.480 line YZ to intersect the previous benchmark. Label the intersection of the 00:09:33.500 --> 00:09:42.460 benchmarks S.B. If the specimen size is insufficient to mark a 500 millimeter -- 00:09:42.480 --> 00:09:47.580 20 inch -- length, mark the longest available length, which is at least 75 00:09:47.600 --> 00:09:53.659 millimeters -- three inches -- below the upper edge of the test specimen. As 00:09:53.679 --> 00:09:58.519 described earlier, the second method uses intersecting perpendicular lines that 00:09:58.539 --> 00:10:03.259 can be expressed as an inverted T marking on garment panels and some fabric 00:10:03.279 --> 00:10:08.289 specimens. The percentage skewness is obtained by how much the inverted T has 00:10:08.309 --> 00:10:13.509 distorted. After laundering, a right angle marking ruler is placed with one leg 00:10:13.529 --> 00:10:18.490 of the ruler placed along the line YZ, so that the vertical second leg passes up 00:10:18.509 --> 00:10:24.210 through point B. A new benchmark is drawn along the perpendicular on line YZ. 00:10:24.230 --> 00:10:30.529 The intersection of the new benchmark and the line YZ identifies point A prime. 00:10:30.549 --> 00:10:35.149 The length of the line AA prime is measured and recorded to the nearest tenth of 00:10:35.169 --> 00:10:39.970 an inch or smaller increment. This distance is the displacement of the right 00:10:39.990 --> 00:10:53.009 angle. The length of line AB is also measured and recorded. Finally, the 00:10:53.029 --> 00:11:02.899 skewness to the left or right is indicated. The percent skewness in this method 00:11:02.919 --> 00:11:07.279 is a simple proportion of the amount of the displaced distance of point A as 00:11:07.299 --> 00:11:13.159 defined by AA prime to the length of the vertical line segment AB. Skewness is 00:11:13.179 --> 00:11:20.129 reported to the nearest 0.1 percent. The equation used is as follows: AA prime 00:11:20.149 --> 00:11:26.269 is divided by AB and multiplied by 100 to give the percent change in skewness. 00:11:26.289 --> 00:11:33.389 In this example, line AA prime was 0.425 inches in length and line AB was found 00:11:33.409 --> 00:11:41.350 to be 18.85 inches. Therefore, the percent skewness is 0.425 divided by 18.85, 00:11:41.370 --> 00:11:47.230 multiplied by 100, and equals 2.3 percent skewness. An important factor in 00:11:47.250 --> 00:11:52.189 skewness is that the longer the garment, the more obvious the skewness. This 00:11:52.209 --> 00:11:56.490 illustration shows a couple of pairs of knit pants made from the same fabric and 00:11:56.509 --> 00:12:01.480 having the three percent skewness for both pairs. Normally this level of 00:12:01.500 --> 00:12:06.590 skewness is considered acceptable. Pair A has an inseam of 10 inches, while pair 00:12:06.610 --> 00:12:13.090 B has an inseam of 30 inches. Therefore, the side seam shown for A is displaced 00:12:13.110 --> 00:12:20.159 0.3 inches. The side seam for B is displaced 0.9 inches. Pair B appears to have 00:12:20.179 --> 00:12:25.840 much more skewness. However, the percentage change is the same. This example 00:12:25.860 --> 00:12:30.043 shows that panel lengths in garments may appear to be worse than the actual 00:12:30.063 --> 00:12:31.749 skewness measured.