Grades 3–5 · Arts & Music
Why does watercolor spread differently on wet paper?
Watercolor contains small pigment particles and a binder mixed with water. When the brush touches paper, it leaves this mixture behind. The movement of the water helps determine where pigment can travel.
In the diagramWater in the paper changes pigment movementRelatively dry paperWet paperinvented deposits; paper, pigment and drying also matterWater can move and evaporate while the pigment leaves a lasting mark.
On relatively dry paper, the wet mark often stays more closely within the area touched by the brush. The paper takes up some water, and the mark can keep a fairly distinct boundary.
On wet paper, the new paint joins water already spread across and within the surface. Flow can carry pigment beyond the first brush mark. Colors can meet and blend, leaving softer boundaries as the water moves and dries.
The final pattern depends on the paper, pigment and changing water supply. Water can evaporate while pigment remains. A soft-edged wash is therefore a record of material moving during drying, not just the exact outline of the brush.
About this explanation
Starting knowledge: Know that watercolor contains pigment carried in water and that paper can hold water between fibers.
Sources
- Winsor & Newton / Colart — A guide to: Watercolour techniques