What is the primary feature of non-waterproof ink?

The primary feature of non-waterproof ink is that it absorbs into the paper. This property allows the ink to spread slightly upon application, creating soft edges and a more fluid appearance in line work, which is particularly favored in calligraphy and sketching. Because it is designed to be absorbed rather than sitting on top of the paper, non-waterproof ink is often used for techniques that involve blending and shading, where the deeper penetration into the paper enhances these effects.

In contrast, other types of inks, such as waterproof inks, remain on the surface and do not absorb, making them ideal for certain applications where water resistance is required. The options regarding glossy finishes, ink washes, and color range pertain to characteristics found in different types of inks but do not directly define the absorptive nature that characterizes non-waterproof ink. Thus, the absorption property is the key distinction that defines non-waterproof ink's primary feature.