How to Write Watercolour Image Prompts - Nano Banana 2

Loose watercolour is wet-on-wet: soft blooms, colours running into each other, edges that dissolve, large areas of untouched white paper. Tight watercolour is wet-on-dry: crisp edges, controlled washes, fine ink linework over the top. Botanical illustration and children’s book art both count as watercolour, and they look nothing alike.

Say which one you want in the prompt. “Loose wet-on-wet watercolour, colours bleeding into each other” and “tight botanical watercolour with fine ink linework” are two different pictures, and neither of them is what you get from typing “watercolour painting” on its own.

Paper texture is the companion detail. Cold-press paper with visible tooth catches pigment unevenly and gives that slightly grainy look. Hot-press is smoother and lets edges stay crisp. Naming one tells the model something concrete about how the surface should behave.

Subject matter also fits the medium better or worse. Watercolour handles landscapes, plants, animals and loose figures beautifully, and struggles with hard mechanical surfaces — which is a useful thing to know before you spend twenty attempts trying to get a watercolour spacecraft to stop looking like an airbrushed poster.