PITT artist pens use India Ink that is acid free, permanent, waterproof when dry and odorless. They will not bleed through paper like traditional markers. The durable nib gives the freedom to create verstaile ink brush strokes of broad, medium to narrow with an even application of color. It can be refreshed by simply removing the nib and turning it over to reveal a fresh point! Great for all types of surfaces including canvas, fabric, wood and ceramic.