How can a pen create both delicate and forceful lines?

A pen creates varying line qualities primarily through the interaction between the tool's physical construction and the artist's manual control.

The ability to produce delicate or forceful lines depends on several factors:

• Pressure and the Split Tip: The pen functions via a capillary effect. When using a split-tip pen, the amount of drawing fluid transferred to the surface is directly influenced by the pressure exerted by the artist's hand. Stronger pressure on a split tip can cause it to fork or spread, resulting in a powerful, hard stroke, while lighter pressure produces thinner, more delicate lines.1
• Tool Selection: Different pens offer different ranges of expression. A reed pen is known for its characteristically powerful and hard strokes, often used for bold, plastic accents. In contrast, a quill pen features a supple tip that allows for a wider scale of expression, ranging from soft, thin lines to energetic, broad strokes.1
• Stroke Differentiation: Artists can manipulate the "waxing and waning" of a line—thickening or thinning it—to indicate spatial changes, light, or shadow. By varying these stroke layers and combining different types of pens, artists can achieve subtle plastic characterizations and expressive depth.23