20ml Dark Cave ink for dip pens, offering a smooth writing experience. - Brand: Dipton - Ink Type: Dip pen ink - Color: Dark Cave - Capacity: 20ml Thank you for viewing. Not for fountain pens, this ink is suitable for glass pens. Dark cave ink is a shimmering ink that produces a metallic sheen of a different color from the ink color in areas where the ink pools. Used, but the capacity has not decreased much.