Can I Disable Canvas Textures?

Hi everybody.  I'm using Painter X and I was wondering if there's a way to turn off the texture of canvas and paper.  Sometimes i want a completely smooth surface, like when I'm using the scratchboard tool for comic-book style inking.  The texture of the ground layer can sometimes interfere with the look I'm trying to achieve.  I've tried using all the textures in my library and none of them are as smooth as I need.