According to another preferred embodiment of the present invention, a polyurethane mixture is provided, including a slurry that includes about 33% castor oil, about 61% calcium carbonate, about 2% ethylene glycol, about 2% glycerin, about 1% to 2% titanium dioxide, about 0.1% desiccant, about 0.1% to 0.2% organotin, and an isocyanate mixed with the slurry such that the isocyanate forms about 20% t