Alder Wood (Traditional) Moving Sand Art Pictures: Volcanic Clear / SmallMoving sand pictures. The double strength glass is framed with a quality knotty alder wood frame. The black sand is heavier than the white sand so the two will never mix, some of the sands are transparent and some opaque giving the pictures a cool 3 d effect. Pictures may take from minutes to several hours to finish a magical landscape, tiny air bubbles hold up the sand creating unique natural scenes with every turn. Choosing the perfect gift for any