paillon

from The Century Dictionary.

• noun Bright metal foil, used in decorative art to show through a thickness of enamel or painting to alter its color or give it brilliancy; by extension, gilding applied upon a surface, as of wood, papier-maché, etc., upon which painting is to be done in translucent colors.

from the GNU version of the Collaborative International Dictionary of English.

• noun A thin leaf of metal, as for use in gilding or enameling, or to show through a translucent medium.