Dr. Ph. Martin’s Hydrus Fine Art Watercolor is a range of lightfast, transparent, brilliant, acid free, archival grade, pigment based, non-clogging, intermixable, non-toxic, lightfast, high quality artist watercolours, designed specifically for use with technical pens, fountain pens, calligraphy pens, and drawing pens. These inks are formulated for use in dip pens but also works well with brushes and airbrushes. They are ideal for design and illustration.