The main theme in his artwork is the body- he is interested in the forms, curves, their saturation and the space being a tension zone. The body as a source of volume and space, where the light is absorbed on falling by the skin. His paintings attempt to convey the ephemerity, fineness and corporeality of the epidermis, requiring special attention. Castillo reaches for the vibration of the living body through the blendage of multifarious colours thus impressing vivid manifestation of the figures - they radiate sensuality. The extraordinary technique he applies plays a great part in the creation of his masterpieces. The canvas, used in his works is squashed and clayed, sticked with glue, which conveys the feeling of antique leather or pergament.