The coolest setting on an iron is usually around 275 degrees Fahrenheit, while the hottest setting is usually around 445 degrees Fahrenheit. Fabrics like acrylic and nylon should be ironed on a low setting so that the fabric doesn’t get damaged.
Acetate and silk are two other fabrics that should be ironed on a low setting. Find the temperature knob on the front of the iron to turn it to a low setting. If the knob has a number scale to show temperature settings, turn it to 1 or 2 for the coolest temperatures. Some irons also tell you what kind of fabric each setting is best for.