Gouache is a type of opaque painting that consists of pigment and a binding agent. These paintings are also often referred to as opaque watercolour. Similar to watercolours, gouache can be diluted with water and applied in semi-transparent layers.
Watercolor allows the artist to apply thin washes, or layers of color, building a surface of color one layer at a time. Gouache, on the other hand, can come in a small tube or as a pan (like watercolor), can be thinned (like watercolor) but even when it is thinned has a different characteristic to it. The opacity of gouache grants you certain things that watercolor won't, and vise versa.
With watercolor you can:
- Achieve luminous areas of color with many transparent washes
- Keep a pencil or (waterproof) pen drawing underneath the paint
- Play with color by layering and glazing
- Do quick field sketches
Gouache, on the other hand, allows:
- Greater ability to cover up mistakes, due to the opacity of the paint
- Effective covering of large spaces if you trying to get a flat area of color
- Great outlining and lettering
- Painting on toned paper
- An almost dusty, matte finish
Try using both similar projects to find out which you prefer. They can often be used interchangeably, together and layered on top of each other to achieve truly unique effects.
Both mediums can take extensive practice to master.