There is only one reason your t-shirt is not changing color: YOU ARE TOO COLD!!!!! 1. You must wear the t-shirt to make it change color. 2. If you want the t-shirt to be more reactive because either you are in a cold climate or you are cold, put your t-shirt in a machine dryer on warm until the t-shirt changes color. This will heat up the cotton fibers so it is more reactive.

YES. Wash with light colors in a machine dyer on Warm, no bleach.

YES. You can dry your t-shirt in a machine dryer on Warm. DO NOT DRY IN DIRECT SUNLIGHT. PRELONG EXPOSURE TO SUNLIGHT WILL DESTROY THE COLOR CHANGING EFFECT.