Once your project is completely dry, you can seal acrylic paint with heat by putting your piece into your dryer (by itself to ensure the paint doesn’t bleed at all), or with an iron. If you choose to use an iron, set the iron on medium heat with no steam. Turn the pillow cover inside out. Place a press cloth inside, between the front and back of the cover and iron the reverse side of your stenciled design. Iron for about 3 minutes, moving the iron back and forth. Be careful as the fabric will be hot.