Derwent-Inktense Pencils. Derwent Inktense Pencils are our best water-soluble pencil ever! You can use them dry but mix them with water and the color turns into vibrant ink. Once it is dry the color is fixed and because it is permanent and great for using on fabric such as silk and cotton. This package contains seventy-two pencils in an assortment of colors within one tin. Conforms to ASTM D4236. Imported.