Shirt stiffener is a term used to describe a product that is used to make shirts look crisp and neat. STARCH is a common type of shirt stiffener, which is a white powdery substance made from wheat, corn, or potatoes. It is applied to the fabric of the shirt and then heated to create a stiffer texture. STARCH can also be used to make other fabrics such as curtains and tablecloths look more crisp and neat.