Heat Didn't Shrink That Shirt:
Allow the water to boil.
Next, heat is your biggest enemy, especially when it comes to clothes made of cotton, mohair or wool.
Drying it inside is a much safer way.
The cold water will wash the t-shirt and will not cause it to shrink.
The best known characteristics of cotton are that it is natural, breathable, comfortable, and that it shrinks.
Looking for preshrunk shirts will save you from the shrinking problem.
However, you should have in mind that preshrunk shirts might shrink a little, but still, not as much as the rest of the shirts.
Turn off the heat from the stove, then carefully dump the boiling water and the shirts from the pot into a sink or tub.
Carefully pour the water from the pot down the drain.
As for drying, ideally, your clothes made from natural fiber materials should never be introduced to the inside of your dryer.
When you wash the entire shirt, use only cold water.
Simply rub the soap across the area and rub the t-shirt repeatedly under the running water.
Place the cotton shirts in the water.
However, there are ways to get the t-shirt to remain at its original size and to keep shrinkage at bay.
Cotton can shrink under the right conditions, so if you have a cotton shirt that is a tad too big, you can shrink it.