A painting medium it will not mix such as oil and water, or water and resin, unless combined by the addition of an emulsifying agent. Emulsifying agents can be &#39;natural&#39; such as egg-yolk, albumen and lecithin. Source: Ralph Mayer, "A Dictionary of Art Terms and Techniques" <br><br>A liquid in which small droplets of one liquid are immiscible in, but thoroughly and evenly dispersed throughout, a second liquid. eg. Acrylic Emulsion<br><br>Casting of light-sensitive chemicals on papers, films, printing plates and stencils.<br><br>A suspension of small globules of one liquid in a second liquid with which the first will not mix. A photosensitive (light sensitive) material which consists of a coating of silver halide grains in a gelatin layer, on photographic metal plates (for a daguerreotype), glass plates, film, fabric, paper, or other surfaces.(pr. &#601;-MUL-sh&#601;n)Also see emulsifier, negative, photography, positive, and stain.