Here are the instructions for the cover of our memory foam mattress:
Remove cover (well, duh!).
Hand wash or machine wash on delicate cycle.
Use cold water only.
DO NOT BLEACH.
Air dry on flat surface or machine dry using cold air only.
Thorough drying may take several hours.
Dry cleaning recommended.
Here's how I washed it yesterday, having not noticed the above instructions on the bottom edge of the mattress:
Washed in regular machine cycle.
With HOT water!
...and I used bleach, too.
Dried in the dryer on the normal hot cycle.
It was dry in about 20 minutes.
And yet, it came out alive and fit back on the mattress just fine.
In closing, let me just say that this is the best mattress I've ever slept on. So next time, I'll be sure to take better care of its precious cover.