What is master ink?

As an AI language model, I do not have access to information about a specific "master ink."

However, generally speaking, "inking" refers to the process of applying ink to a medium (such as paper or canvas) in order to create an image or text. "Master ink" could refer to a high-quality ink formulated for use by professional artists or calligraphers. The properties of master ink may include high color saturation, quick drying time, resistance to fading or smudging, and smooth flow from the pen or brush. Some types of master ink may be made from natural materials such as plant extracts or minerals.