Ultraviolet barrier and high build primer/filler EkoFill is a water base latex material mixed with flumed carbon. This combination not only makes a high build primer that remains extremely flexible, but also provides an excellent ultraviolet barrier for your fabric or composite surface. EkoFill is a perfect primer/filler over polyester fabric, glass cloth, gel coat, composite materials, etc. It has excellent adhesion to these surfaces and superior high build properties to fill in small imperfections or the weave of a fabric. It sands easily to an ultra smooth finish. Just perfect for Stewart Systems Waterborne Two-Part Polyurethane Topcoats. Probably the most important reason for using EkoFill is that it is a proven ultraviolet barrier for those sun sensitive products used for aircraft construction. As most of you may or may not know, there are two common conditions that will destroy most synthetic fibers. One being excessive heat above 400¦F, the other being ultraviolet rays (sunlight). The flumed carbon in EkoFill is a perfect and natural way to protect your project from harmful UV Rays and like all our products it is safe to use, pleasant to smell and you clean-up with water.