Sketcho Oil Crayons can be blended with your fingertips or layered to give the effect of oil paint. Sketchos are recommended for drawings and outdoor sketching. These versatile oil crayons can be used in a variety of ways, are great for the classroom or for at home projects, and are AP Certified non-toxic. Great art starts with great products. Louis Prang developed child-safe art products that uphold the highest standards of quality in materials and colour. These standards are maintained today in a comprehensive line of Prang art products for both children and professionals.