Answer:
Cross-hatching technique
Explanation:
The portrait seems to be done in the pencil using the cross-hatched technique.
It is the variation of the hatching technique which uses lines positioned at different angles to produce different tones, textures, and illusions of depth. The lines can meet at any angle, but the simplest one is at 90°. The darker shadows and tones can be created also by the thickness of the line, the spacing between them, or adding layers.
