I have used pumice in my dental practice for over 40 years. It is used to polish acrylic appliances (ortho. retainers, dentures, partials). I used two grades and both were far finer than the finest sand. You are using a far different pumice. I have never seen sand act like cement. Its just........sand. It drains the same after one day or one year. I have never seen a "cement" beach.
