Certain material seems to be more susceptible to wrinkles than others. And while some materials are hassle-free and wrinkles are easily removed, other types, such as collared polo shirts, can be a bit more tricky. This is especially true of getting creases out of the collars of polo shirts. Even though creases can be ironed out, they don't always disappear and tend to make their appearance at the back of the collar.
Wash the shirt according to laundering instructions. Put the shirt in the dryer, but do not allow it to dry completely. Put the iron setting on cotton and enable the steam mechanism. Place the shirt on an ironing board and iron the collar flat, using the steam button, as you press the iron onto the shirt. You can also do this with a shirt straight out of the washer; just allow it to drip dry afterward.
Mix equal parts vinegar and water in a spray bottle before ironing the collar a second time. Spray the mixture on the shirt. The steam mechanism should still be engaged. Go over the collar again, pressing hard on the collar as you run the iron over it.
Pass the iron over the shirt collar three to four times, spraying the vinegar and water mixture on it between passes. Allow the iron to linger on the collar in each spot for at least three seconds before you continue the task. Lay the shirt flat and allow to dry completely.