Prang - DIX51000 Soft, grit-free, molded chalk features an intensely rich, colorful and smooth laydown on paper, cardboard and other smooth or toothed surfaces. They blend easily for an array of colors. Versatile chalk works well on wet or dry mediums. Use them for posters, murals, stage props, sketching and other art projects. They are not recommended for chalkboards. Flake chalk into water for a unique marbling effect. PMA-certified, nontoxic construction is safe for children.