Homemade laundry starch is usually a simple solution of powdered cornflour and water. Commercially produced liquid starches add preservatives, sizing and scents to this standard solution according to patented recipes that may differ with each manufacturer. Older starch formulas may have contained other plant-based stiffeners, such as wheat or potato starch. All starches add stiffness to clothing and make ironing easier.
Homemade Liquid Starch
Combine powdered cornflour with an equal amount of cold water. Add this paste to 2 quarts of boiling water. Allow the solution to cool to room temperature. Dip cotton shirts in the starch solution, wring them dry, and iron at a medium temperature (cotton setting). For four shirts, use 2 quarts of water combined with 1 1/2 tsp, 1 tbsp or 2 tbsp of cornstarch for light, medium or heavily starched results.
Homemade Spray Starch or Sizing
In a spray bottle, combine 2 tbsp powdered cornflour with 1 pint cold water and shake thoroughly. Spray clothing as you go and iron at a medium (cotton) setting. For fabrics that require a lower heat setting, sizing is required. To make sizing, combine one package of unflavored gelatin in 2 cups of hot water. Dip the clothing into the gelatin solution and allow the fabric to dry. Iron at a low (synthetic) setting. Sizing is substituted for starch when ironing synthetics and delicates.
Commercial Liquid Starch
The ready-made liquid starch you buy at your local grocer or convenience store is made using a formula similar to homemade liquid starch but with the addition of a few patented ingredients. Preservatives prolong shelf life, sizing extends the product's range of use and scent adds a pleasant aroma to the ironing experience. Commercial sizing is a variant of carboxymethylcellulose, a derivative of natural cotton.
Effects of Starch
Apply starch to clothes before or during the ironing process to add stiffness and a glossy surface that helps to prevent dirt from penetrating fabric surfaces. Starch helps a hot iron to glide smoothly over fabrics, making the ironing process less physically taxing. Many modern fabrics have been chemically altered so that wrinkling is less of a problem, and ironing with or without starch is no longer necessary to keep a well-groomed look.