One of the best creative mediums I've discovered as an artist is Powertex!  Powertex Textile Hardener is an environmentally friendly,  liquid sealent that when painted on virtually any surface (fabric, canvas, yarn/rope, clay, paper, leather, styrofoam, natural/organic materials, wood, cement, ...) makes the object waterproof/weatherproof.  It's simple to use by painting, sponging, or dipping, has no offensive odor, and dries quickly.  Available in Terra Cotta, Bronze, Ivory, Grey, or Transparent, there is a color option for almost any sculpture or mixed media project.   I love to use Powertext to create unique artwork for display in my yard.    A couple of outdoor art projects I've protected with Powertex include a large lizard made from Makin's Clay over an armiture of recycled materials, and a colorful whimsical butterfly made with recycled materials and colorful fabrics.   Bronze was used on the lizard.  While some of the transparency of the shear fabric used on the butterfly wings is lost after applying the transparent Powertex, the beautiful graded colors still shine through.  To learn more about the entire line of Powertex products visit their website at www.PowertexUSA.com.