An acrylic-based pigmented water-resistant inks (on most surfaces) with a 3 or 4 star rating for permanence high degree of lightfastness and are fully intermixable. Alternatively dilute colors to achieve subtle tones very similar in character to watercolor. Such washes will dry to a water-resistant film on virtually all surfaces and successive layers of color can be laid over. Works well through airbrushes and technical pens. 1 oz. Prussian blue.