There are numerous ways to change a watercolor wash from a flat wash to an area with texture.
I have used cadmium red as the base for these washes since it is a bright color.
In the top row on the left, I made a flat wash and left it alone.
In the top right rectangle, I sprinkled table salt into the damp pigment. Little star-like shapes appear in the wash and the salt may be brushed away after the wash is completely dry. Larger crystals of salt will leave bigger star shapes.
In the middle row, I sprinkled the damp wash with water (on the left) and alcohol (on the right). These produce “run backs” in the paint, with alcohol producing a more subtle result.
In the bottom row, the damp wash was covered by pieces of crumpled plastic wrap (left) and wax paper (right) which are removed after the paint has dried. The plastic wrap produces a more angular abstract texture than the wax paper.
Many other items may be used to introduce texture and are all part of a watercolor artist’s arsenal of illusions in turning paint and paper into a piece of art.