A pillow can feel dry outside while the middle is still wet.
The Middle of a Pillow Dries Last
How to wash pillows and a comforter, and how to tell they're dry all the way through.
Press a pillow that just came out of the dryer, and the outside feels dry. The middle can still be damp.
Damp filling is what turns a fresh pillow musty, so most of this post is about drying. A few steps before it make drying easier.
Read the care label
Read the care label on each pillow and on the comforter. Memory foam can't go in a washer or dryer, so wipe it with a damp cloth and mild soap and let it air dry.
Water and heat break foam down, and a foam pillow can stay wet inside for days.
Wash gently with a little detergent
Wash two pillows together, or the comforter alone, on a gentle cycle with a small amount of mild detergent. Use a large washer if the comforter doesn't fit loosely.
Two pillows keep the drum balanced. A crowded drum can't rinse the soap out, and soap left in the filling makes it clump.
Run an extra rinse
Run an extra rinse if your washer has one.
Thick filling holds on to soap, and a second rinse carries more of it out.
Dry on low heat with dryer balls
Empty the lint filter, then dry on low heat with wool dryer balls or clean tennis balls in the load. Stop about every 30 minutes to fluff and turn the pillows.
A clogged lint filter can start a fire. Low heat protects the filling, and the balls break up clumps so heat can reach the middle.
Check the middle before you use it
Squeeze the center of each pillow and press into the middle of the comforter. If any spot feels cool or damp, or the filling stays in clumps, dry it for another cycle.
Damp filling grows mildew, and a musty smell is the first sign.
Short on energy?
Just read the care label on your pillows. That's enough for today.
The larger lesson
The washer does the easy part. The dryer decides whether a pillow ends up fresh or musty, because filling holds water in the middle long after the surface feels dry.
If the middle is dry, the rest is too.