I bought crushed walnut shells at a nearby chain pet store. They are in the reptile supplies area, used for pet bedding. It was a much larger bag than I needed, but it didn't cost much at all. I had not heard about washing it, but I don't see why you would. Some people are concerned about those with nut allergies receiving a pin cushion filled with walnut shells. If I were making pin cushions to sell or give to a large group of people, I would just make people aware that they contains nuts products. The shells make a really nice pin cushion filler.