Read the label on commercial laundry starch and you'll find that corn starch is the main ingredient. Corn starch, made from the inner grain of corn, thickens pie fillings and puddings, but it also starches shirts and clothing for a crisp, finished look. To make laundry starch for the washing machine, simply mix corn starch with cold water. Experiment with the amount of corn starch you add; larger amounts result in crisper, stiffer laundry.
Dissolve corn starch with 1/2 cup cold water in a bowl. Stir it until it is completely dissolved.
Add 3 cups hot water to the mixture and stir again to mix well. Corn starch dissolves best in cold water, but the hot water thickens it slightly.
Pour the mixture into a jug or covered container for storage. Shake before use to thoroughly mix it.