Art Alternatives - Gallery Stretched Canvas (1.5in) - 18x18 - Natural, unbleached medium-weight cotton duck is stretched around specially designed, kiln-dried stretcher bars, and held in place with a flexible spline allowing these canvases to be painted on all four edges as well as the canvas surface. The surface is triple-primed with acid-free acrylic titanium gesso and staple-free on the sides. Gallery Stretched Canvas features a thick 1-1/2 in. edge. It is suitable for oil and acrylic painting.