Each Pitt Artist Brush Pen uses the finest quality, permanent Indian ink, which is acid free and archival. The Waterproof ink incorporates high quality pigments with unsurpassed lightfastness. The quality brush provides flexibility for sketches or detail work.Ink drawings have a long history amongst artists. It has great covering properties along with resistance to ageing, and you can combine these pens with other painting methods. This has always been an interesting medium for artists and graphic designers. These Pitt Artist Brush Pens are excellent for colouring, sketching and mixed media.Ink drawings have a very long artistic tradition. This has always been an interesting medium for artists and graphic artists, it lends drawings expression and durability and can also be combined with many other drawing techniques. Faber-Castell has combined all the advantages of artist\'s inks with the benefits of a modern, easy-to-use disposable pen - the PITT artist pen. The pigmented and very lightfast drawing ink is ideal for sketches, drawings, layouts, fashion design and illustration.Pigmented India Ink Extremely Lightfast Waterproof & Permanent Odorless, Acid-Free & pH Neutral- Set of 6 Terra