The Beta Series from Stillman & Birn features high performance paper designed for mixed media applications The extra heavy-weight paper has a white cold-press surface that is suitable for all dry media and ink, as well as watercolor. In fact, they state Beta "lets artists drench their sketchbooks in water and pigment and try audacious new techniques." The wirebound hardcovers are made with extra heavy-weight binders' board that is tough and resistant to warping. The paper contains both internal and surface sizing, is pH neutral, lignin and chloride-free, and 270 gsm thick. Each book contains 25 sheets.