Sfumato

Using smoke / Fire to add shading or tone to his pictures Charles creates a unique style that echoes ancient cave paintings and Chalk Cuts.

Britannica Definition:
From Italian sfumare, “to tone down,” or “to evaporate like smoke”), in painting or drawing, term designating fine shading that produces soft, imperceptible transitions between colours and tones. It is used most often in connection with the work of Leonardo Da Vinci and his followers, who made subtle gradations, without lines or borders, from light to dark areas.