Gouache is a unique painting medium. It is a water-based paint that can be used like watercolor with thin washes, but it is opaque enough to be used like acrylic. These characteristics allow gouache to be used in a variety of different ways on a variety of different surfaces.
Gouache has been around for quite some time, tracing its roots back to the 14th century. It's body is thicker than watercolor paint and the ratio of pigment to binder is much higher making the paint more opaque than watercolor. It can be used with heavy solvent (water) to produce watercolor effects, or it can be applied with no thinning at all to produce completely opaque applications.
Because it is opaque, paint can be applied in layers to a certain degree. When layering is used, expect some of the color applied on under layers to show through. Gouache can be "reactivated" when water is added, so each layer "reactivates" the color underneath a bit.
When used as a watercolor, transparent washes can be used. Although, even coverage of pigment is a bit harder to achieve with gouache. I suspect this is due to the larger particles of pigment in gouache.
I have found most success when using gouache as a watercolor in the early stages of a painting, and then switching to more opaque applications as the painting develops. Each artist will approach gouache differently, but this approach allows me to create an underpainting first. I can develop the values first and then layer local color over them.
Gouache can be used in conjuction with other materials as well. Other water-based paints including watercolor, acrylics, and tempera will all "play well" with gouache. Drawing media like colored pencils and soft pastels also layer nicely over dried areas of gouache.
Gouache can be used on a variety of surfaces. Most comonly, heavy paper such as watercolor paper or Bristol paper is used. Other suitable surfaces include masonite and canvas.
The featured video is excerpts from a 1 hour Live Lesson on painting with gouache. To see the full one hour demonstration (available to members) click here...