Sakura Pigma Micron pens are both acid-free and archival, giving the artworks created with them with lasting quality. They will not run if liquids are spilled on or applied to the artwork after the ink has dried. These pens are ideal for any application requiring precision and permanence, such as papercrafts, journals, illustration, crafts. Manga artists, professional illustrators and watercolorists can use them to create lines with precision.Even through the thinnest paper Pigma ink will not feather or bleed. Pigma ink is derived from a single pigment to ensure color consistency, and is fadeproof against sunlight or UV light. Pigma inks will not clog or dry out.Please note that Sakura Pigma Micron pens are not refillable. The Micron Pens have colored coded ends for easy color identification.pdf=PigmaInk.pdf More information on Pigma Ink