The use of gouache is not restricted to the basic opaque painting techniques using a brush and watercolor paper. It is often applied with an airbrush. As with all types of paint, gouache has been used on unusual surfaces from Braille paper to cardboard. A variation of traditional application is the method used in the "gouaches découpées" (cut collages) created by Henri Matisse. His "Blue Nudes" series is a good example of the technique. A new variation in the formula of the paint is "acrylic gouache".