FUNDAMENTAL PRINCIPLES THAT GOVERN THE SHRINKAGE OF COTTON GOODS BY WASHING

This article outlines the reasons cotton fabrics shrink, and gives many numerical examples. The length of cotton fibers change less than 1 percent from 45 percent relative humidity to wet, but diameter swells 14 percent. Unlike wool or rayon, contraction of cotton fibers does not contribute to shrinkage. Yarns of ordinary twist (5) will shrink only 2 percent due to swelling of fiber diameter, insufficient to explain most shrinkage. Shrinkage arises because of crimp in the weave. When threads swell, the warp threads must crimp more; the cloth shortens. If, as in poplin, warp direction is pulled during wetting and drying, warp crimp interchanges to the weft threads. Crimp will revert on next wetting, with warp shrinkage of 10 percent or more possible. Quick immersion tests can be misleading, if the fabric is not easily wetted. Hot solutions will wet sized fabrics better. Ironing can restretch shrunken cloth. Successive washings reach a limited shrinkage, but most occurs in the first wash. An appendix describes models of wood, tubing etc that demonstrate these causes of shrinkage. Shrinkage due to crimp in wet linen has explained tenting in oil paintngs on canvas.