Wash it Regularly
It is a good idea to wash your HankyBooks regularly. When they’re used and then left out for a long period of time, dirt tends to settle in. You don’t want that.
Just keep it simple. If you don’t use your HankyBook that much, throw it in your laundry whenever your laundry cycle would call for you to wash your clothes anyway – it’ll keep it nice and clean, and the fabric actually gets softer as you wash it. If you do use it a lot – well, simple enough, wash it frequently (but try to wash it with full loads of laundry to conserve water and energy).