From the manufacturer:
Turn nearly every surface, wood, metal, ceramic, plastic, glass, board and more, into one ready for painting with watercolors!
Rescue a watercolor painting, Titanium White Watercolor Ground acts like a "white out" for artists allowing you to cover up with the Ground and start over in an area with fresh white.
You can paint with watercolors on colored Watercolor Grounds; Buff Titanium, Mars Black, Iridescent Gold, and Pearlescent White.
Transparent Watercolor Ground allows the surface of your substrate, for example wood grain or decorative paper, to show through when you paint over with watercolors.
Add texture to your surface with Watercolor Ground.