Experiment 60—How to Determine the Count of Yarn in Cloth
Apparatus: Scales, ruler.
Material: Samples of fabrics.
Reference: Textiles, pages [144-146].
The United States Government imposes a tax on certain imported fabrics and yarn. In the case of cotton, the rates of duty are to be ascertained according to the average number of the yarns in the condition in which it is imported.
The length of the yarn is to be counted as equal to the distance covered by it in the cloth, all clipped threads to be measured as if continuous and all ply yarns to be separated into singles and the count taken of the total singles; any excessive sizing is to be removed by boiling or other suitable processes. The number of the yarn is the English number of 840 yd. to a lb. for a No. 1 yarn.
The average number of yarn may be found without unraveling the fabric, and is the quotient of the total thread length, by the weight in the proportion of 840 yd. of yarn equaling 81/3 grains, which is equivalent to a No. 1 yarn.
The following simple formula may be used:
Multiply the count of threads per square inch by the number of square inches in the sample used, this product to be multiplied by 100; then divide the product thus obtained by the weight of the sample in grains multiplied by 432. The quotient will give the number of the yarn.
For example, take a sample of cotton cloth 4 in. square, which equals 16 sq. in., having 28 warp and 28 woof threads, a total of 56 threads to the square inch, and weighing 8.6 grains. The formula applied would be as follows:
56 × 16 × 100 ÷ 8.6 × 432 = 24, the number of the yarn.
The formula may be further simplified by weighing a square yard of the cloth and dividing the number of threads per square inch by 1/300 of the weight per square yard in grains.