Holbein Acrylic Ink keeps a consistent color from when it flows off your nib till the ink is dry. This super smooth-flowing ink comes in bold, brilliant colors and works great whether you’re using a dip pen, a fountain pen, a technical pen as small as .01mm, a brush, or a refillable marker. It mixes well and works with most other water-soluble media. Each bottle contains a mixing ball for easy reconstitution. Conforms to ASTM D-4236. *Pearl colors are not for use in markers or fountain and technical pens. Price, permanence, and opacity vary by color.