as always, when doing any type of therapeutic tool, i would make it washable. the blanket sites show polystyrene pellets or glass beads inside them... while they may be advertised as washable, it is much better not to have to wash them any more often than necessary or the pellets will break down in time. why not make the weighted part of the blanket between two sheets and then make something similar to a duvet cover with all the cute things you want to do that will button or zip or velcro off and wash quickly and easily.