Gouache is characterized as an opaque medium with which combination?

• A. Gum arabic binder without filler; cannot be rewet.
• B. Animal glue binder; always transparent.
• C. Gum arabic binder with a filler to increase opacity; can be rewet.
• D. Acrylic binder; dries instantly.

Answer: (C)

Opacity in gouache comes from a filler added to a gum arabic binder. The filler—like chalk or kaolin—increases light reflection, making the paint look opaque when it dries. At the same time, the gum arabic binder keeps the film water-soluble, so the dried paint can be reactivated with water for edits or future layers. This combination—gum arabic binder with a filler to boost opacity while remaining rewettable—fits gouache best.

Without the filler, you’d get a transparent watercolor feel; using an animal glue binder wouldn’t produce the typical gouache opacity; an acrylic binder would lead to a different, usually faster-drying, acrylic-based product rather than traditional gouache.