BLACK MAGIC INK 70 is the new secret recipe, to go all city. Supplied in a shockproof plastic dark bottle, is the top choice for refilling our GROG Purple Label markers. BLACK MAGIC INK 70 comes filled with 70 ml of alcohol and water-based dye invisible ink, optimized for CUTTER markers, which reacts only under UV lights until it turns into a deep dark brown satin finish. Ideal for both indoor and outdoor sessions, it works on porous surfaces only.