Robert Oster Thunderstorm Fountain Pen Ink — 50 mL

Robert Oster Thunderstorm is a dark blue-grey to blue-black, the color of a sky carrying more weather than light. Fine nibs can make it look nearly black; broader writing reveals the blue and grey beneath.

Reviewers agree on its dark, well-lubricated character but differ on sheen: some find none in ordinary writing, while heavy swabs can show maroon or greenish sheen. Medium-to-high shading is more reliable than sheen as a normal writing property. Flow is moderate and water resistance is low.

Ink character

• Color: dark blue-grey / blue-black
• Shading: medium to high
• Sheen: variable; most evident in heavy pooling
• Shimmer: none
• Flow: moderate, well lubricated
• Water resistance: low
• Best suited to: work notes, long-form writing, correspondence

Thunderstorm is one of the quieter Robert Oster colors: professional at a glance, but full of blue-grey variation when you spend time with the page.