The soft fine wool of a cashmere sweater is easily stretched out of shape. Dry cleaning the sweater will prevent it from stretching or shrinking in the wash, but it does little to return a sweater to its original size. A gentle wash and a reshaping will help restore a cashmere sweater to its original condition. If reshaping is not sufficient, make some minor alterations to tighten stretched-out bands, cuffs and necklines.
Lay the sweater on a flat surface and push it into its original shape as best you can. It is okay to make folds in the sweater, you are just trying to estimate the original size.
Measure the length of all the seams on the sweater. Measure the width of the sleeve at the elbow and the cuff. Measure the width of the sweater under the arms and at the bottom. Write these measurements on an index card with a description of the sweater.
Wash the sweater in cold water with gentle, cold-water detergent. Wash either by hand or using the delicates cycle in the washing machine. If you use the machine, place the sweater in a large mesh bag. Do not allow the machine to spin.
Squeeze the sweater slightly to remove some of the excess water. Do not wring or twist it.
Lay the sweater on a large fluffy towel and roll it up. Repeat this process several times until the sweater is dry enough to handle. You may gently squeeze the rolled up towel.
Lay the sweater out flat on a double layer of towels. Gently shape the wet sweater to the measurements on the notecard. Allow the sweater to dry.
Turn the sweater inside out. If the neck, cuffs or bottom band are still too large, thread a needle with a large eye with thread elastic and knot one end. Sew the elastic through the stretched out rib knit band to gather it together. Sew by running the thread through the ribs that stick up on the inside of the sweater. Sew perpendicular to the ribs. Add a line of elastic every 3/4 inch along the ribbed band. Turn the sweater right side out.
Save the index card for the next time you wash the sweater. Turn the sweater over when it is almost dry to speed the drying process.