Water miscible oil paint
Water-miscible oil paint is oil paint either engineered or to which an emulsifier has been added, allowing it to be thinned and cleaned up with water. These paints make it possible to avoid using, or at least reduce volatile organic compounds such as turpentine that may be harmful if inhaled. Water-miscible oil paint can be mixed and applied using the same techniques as traditional oil-based paint, but while still wet it can be removed from brushes, palettes, and rags with ordinary soap and water. One of the ways its water solubility comes from is the use of an oil medium in which one end of the molecule has been engineered to be hydrophilic and thus bind loosely to water molecules, as in a solution.
A precursor to water-miscible oil paint is "tempera grassa", an egg tempera method where oil paint is mixed with the tempera and the egg acts an emulsifier to be used for glazing underpaintings and providing added luminosity to paintings.
Handling in comparison with other media
The traditional rule of gradation of layers — "fat over lean," or flexible over less flexible — applies to water miscible oil paint as it does to traditional oil, and in this respect the two kinds of paint behave in the same way. However, their handling is slightly different: when thinned with water to a considerably liquid phase, water miscible oil paint tends to feel and behave like watercolor ; by contrast, when used as a short paste without water for heavy impasto work, it tends to drag, developing a consistency somewhat "gummier" or tackier than the more buttery one characteristic of oils. At midrange water miscible oil paint is gouache-like, sharing the properties of both transparent watercolor and opaque oil. Also gouache-like is the overall effect, which tends to be matte as compared to the glossier oil, but this too is a property that will vary, depending on the pigment used and on any mediums mixed into it, as well as on the pastiness of the paint. The handling of water miscible oil paint, in summary, changes considerably as it passes from one phase to another.