Van Dieman's Professional Natura Dualis - Underflow Dual Tone Fountain Pen Ink captures the subtle power of nature’s hidden currents. This ink features dynamic dual and multi-shading effects, halos, color splits, and rivering that evoke the steady, deliberate movement beneath the surface. Inspired by the quiet strength of tides, Underflow offers a cool, flowing experience on paper that invites close observation and appreciation of its evolving character. Ideal for those seeking an ink that balances visual complexity with refined control.