Encaustic is the oldest painting medium still in use today as it dates back to ancient Greece. Encaustic is comprised of molten beeswax, damar resin and dry pigments or oil paint and is applied to a rigid canvas, wooden panel or metal surface with brushes and palette knives. The wax hardens immediately and must be fused with heat for permanency. Once fused, the durable enamel-like surface is impervious to moisture, dust, shrinkage, fading, yellowing and even cracking (unless the artwork is exposed to freezing temperatures or the support has too much flex). Encaustic paintings do not need to be varnished or protected by glass; a final light polishing with soft cotton is all that is needed to bring out the soft, satiny sheen. The only requirement is that they be hung out of direct sun as high temperatures tend to soften the wax.