First check the fabric care label and follow any instructions. And remember to turn your cashmere sweater inside out before washing.
To machine wash, use the gentlest possible cycle and add a detergent that rinses clean and does not contain any dyes.
Better yet, wash your cashmere by hand. Cashmere is quite delicate, and hand washing helps prevent damage. Mix a mild detergent or a baby shampoo with cool or lukewarm water, and let your sweater soak for about five minutes before rinsing clean.
To dry, lay the wet cashmere on a towel on a flat surface. Don’t wring it out—that can cause the fibers to stretch. Instead, carefully roll up the towel and cashmere item together (like a jelly roll), starting from the end closest to you. This will gently squeeze out any excess water.
Unroll the towel and lift the item off, carefully bringing it back to its original shape. Lay it flat on another dry towel to let it air dry completely.