Stretching a cotton shirt is a simple task because cotton is such a forgiving fiber, but stretching it evenly requires some know-how. People often need to stretch a cotton shirt after it accidentally finds its way into a hot dryer. You can stretch your cotton shirt width-wise or lengthwise.
Fill a large bowl or sink with warm water and about a tablespoon of baby shampoo. Wet the cotton shirt thoroughly by soaking in the warm water solution. Wring the shirt out to remove any excess water.
Spread the shirt out on a large flat surface, such as a countertop or table. Be sure the shirt is completely flat and does not have any large wrinkles.
Run an iron over any graphic-free area on the cotton shirt, using a low heat setting and moving slowly and gently across the fabric toward the outer edge.
Pull the cotton shirt with graphics lengthwise to make the shirt longer. This will automatically make the shirt more narrow through the body or sleeves. To make the shirt wider, gently pull the sides of the shirt away from each other.
Stretch the sleeves by gently pulling either lengthwise or crosswise, depending on desired outcome. If the sleeves are too tight around the arms, pull the sleeves crosswise to stretch. If the sleeves are too short but not too tight, pull the sleeves toward the cuff.
Place weighted objects, such as coffee mugs or bags of rice, on the edges of the fabric to keep the cotton shirt from shrinking back as it dries. Do not remove weights until the cotton shirt is finished drying.