moonsand used to be an indoor activity, but I hated the mess so much that I made it an outdoor activity, I had the kids do it on a blanket in the grass...the moonsand that was left behind, never washed away, or went away EVER...after a year and a half..even when we went to sell our home, the moonsand was still in the grass.....WE sold our house, complete with moonsand filled grass..