Upon first inspection, watercolor and gouache (pronounced “gwash”) may appear to be nearly identical mediums. However, when given more attention, one can see that both paints have individual characteristics that make them easy to distinguish. A primary difference between the two paints is that gouache is more opaque than watercolor. When a layer of watercolor is applied, the white paper and any preliminary drawings underneath will show through, whereas when a layer of gouache is applied, the paper will not show through nearly as much. Due to the transparency of watercolor, the light is able to travel through the pigment and reflect off of the white paper, giving it a luminous quality that differs from gouache’s matte finish.
Despite these differing properties, watercolor and gouache are nearly identical in makeup. Both paints consist of pigment and water soluble binder, which allows the paint to be altered even after it dries with the addition of water. The opacity of gouache comes from the white pigment or chalk that is added along with the colored pigment and binder in order to make it less transparent.
Aspects of technique and purpose of both of these materials can also be compared to find meaningful distinctions. For example, gouache is known to be the medium of choice for many illustrators, while watercolor is more commonly used by other types of artists. This is due to the fact that gouache dries very quickly, allows the painter to easily create large solid blocks of color, and can be used to depict minute details; all traits that are very important to illustrators. Watercolor, on the other hand, is not as controllable and dries much slower. For example, in the piece
by Billy Al Bengston, which is currently on display in Argyros Forum, the fluidity and unruly nature of watercolor is visible. Overall, watercolor and gouache have a number of similarities and differences in appearance, makeup, and purpose that are easy to identify once you are aware of them.