How to Unshrink Cotton Clothes
Even against a person's best efforts cotton clothing, such as T-shirts and trousers, can shrink. According to Cotton Incorporated (see reference 3), cotton will shrink after the first wash because a large amount of tension is applied to the fibres during construction.
Once the cotton piece is washed, these fibres relax and will shrink. It is possible to stretch or "unshrink" a cotton item to bring it back to its original shape and form.
Fill the plastic bucket with one quart of water. Pour one tbsp regular hair conditioner into the plastic bucket.
Place the cotton garment into the bucket, making sure that it is completely immersed.
Allow the piece to soak for 15 minutes. This will help relax the fibres once again, which will make them susceptible to stretching or "unshrinking".
Remove the piece and wrap it into a towel. Roll the towel to wring out the excess water from the cotton garment.
Stretch the item out to a desired size and secure it to a piece of cork board with drawing pins.
Allow the garment to dry. Periodically return to the cotton piece, remove the pins and restretch the piece, and replace the drawing pins until thoroughly dry.