To make polyester stiffen and stand out, starch is required. Starch is extracted from food sources such as corn, rice and wheat. According to Nathan Schiff, PH.D., from FabriCare, the best starch is derived from rice. Read ingredients and purchase starches derived from rice when possible for best stiffening results, although they may be more expensive and difficult to find. Stiffening some polyester blends can be challenging, as they are not particularly stiff on their own. Adding liquid laundry starch to the final rinse of the wash cycle can also help impart stiffness to polyester.
Lay the garment right side out and thoroughly steam iron each section of the garment where you want creases to be stiff and stand out. Clothing should be clean and preferably recently washed. Set the iron to the appropriate setting for polyester fabrics.
Generously spray starch onto the creases you just steamed into the garment. Turn off the steam function on the iron. Slowly move the hot dry iron up and down the crease for up to five minutes. Add more starch as needed to get the desired stiffness. Each time you add starch, use the hot dry iron for a few minutes. The more you starch and iron, the more the polyester will stiffen and stand out.
Starch and iron the collar and along the buttonholes, if your polyester garment is a shirt. Actively stretch the polyester fabric while ironing it to prevent wrinkles, and to ensure that these areas on the garment really stand out.
Define the pleats on the back of a shirt by steaming, starching and ironing them. An alternative is to create a military crease, which can make shirts and a variety of uniforms look professional. Hold both small ends of the collar to each other and fold the shirt along the center of the back. Pinch a crease from top to bottom, lay the shirt on the ironing board and steam iron. Add starch and then dry iron the pleats to desired stiffness.
Lay sleeves flat on the ironing board right side out. Steam the sleeves moving along the seam upwards to create a crease opposite the seam at the top of the sleeve. Apply starch and follow with a hot dry iron to create a stiff crease that stands out.
Iron the rest of the garment and flatten out any pocket flaps with the iron for an overall appearance that looks good and stands out.
Take polyester to the dry cleaner and have him professionally stiffen the material. Use a fabric stiffener purchased from a craft store for use on costumes and clothing that is not important. The fabric stiffener will permanently stiffen the fabric.
Allow your iron to cool down for a few minutes before putting it away. Prevent starch build up on the iron by regularly cleaning the appliance's face.