J.Herbin phosphorescent calligraphy ink 30ml Phosphorescent ink is a fun alternative to add to your calligraphy products. Its properties make it invisible to light but bright in the dark. It is suitable for any type of work in calligraphy or lettering, to use with pens of any type or brushes, but it is advisable to use fairly thick pens. Not suitable for fountain pens. Contains 30 ml. Brand: J.Herbin.