art mediums defined: etching - An intaglio process in which the lowered printing areas are bitten and etched by acid. The drawing and preparation of the plate can be accomplished with a variety of techniques. gouache - Watercolor paints mixed with casein to become opaque. intaglio - A general term covering the printing process such as engraving, aquatint, mezzotint, etching. Any process in which the image is cut, engraved or etched below the surface of the plate. lithograph - A process based on the natural repulsion between grease and water. Image is drawn on stone, aluminum, or zinc plates, or both with greasy drawing materials. The image is then chemically processed so that the drawn area accepts grease (ink) and the non-image area water. The process is repeated for each color needed. serigraph - This process is also known as silkscreen or screen print. A stencil process employing a frame which silk or synthetic fabric is stretched. Stencils such as photo, hand drawn or hand cut are placed on the stretched fabric and act as a block out when the ink passes through the screen by means of a squeegee onto the paper, the non-stencil areas create the image.