Water miscible oil paint
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Water-miscible oil paint (also called water-soluble oil paint or water-mixable oil paint) is oil paint either engineered or to which an emulsifier has been added, to be thinned and cleaned up with water. These paints make it possible to avoid using 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. Its water solubility comes from the use of an oil medium in which one end of the molecule has been altered to bind loosely to water molecules, as in a solution.
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 (although, unlike watercolor, and to a greater extent than traditional oil, it may lose adhesion to the ground or support if over-thinned); 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 (between short paste and long paste) water miscible oil paint is gouache-like, sharing the properties of both transparent watercolor and opaque oil (in the manner of watercolor, for example, some colors will darken upon drying, the more so as more water is mixed into the paint, and in the manner of oil, the paint film will have some thickness to it). 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 (or diluents) mixed into it, as well as on the pastiness of the paint (as a general rule, the pastier, the glossier). The handling of water miscible oil paint, in summary, changes considerably as it passes from one phase to another: this makes it a versatile medium but, by the same token, it also requires the artist to develop by experience specific skills with which to successfully manipulate it and exploit its range to achieve the desired effect.
Although the practice of mixing water-mixable oils with acrylics is possible (as some brands claim), it is not recommended if the painting's longevity is a concern. The reason is that once the acrylic dries, its impermeability isolates the oil from oxygen, preventing it from oxidizing properly.
There are several manufacturers producing water miscible oil paint, including: Daler-Rowney —(Georgian Water Mixable Oil) Daniel Smith (Water Soluble Oil Colors), Grumbacher (Max Water Mixable Oil) Holbein Works (DUO), . Lukas (BERLIN), Martin F. Weber Co. (wOil), Reeves (tube sets and complete painting set), Royal Talens (Cobra Artist and Cobra Study), and Winsor & Newton (Artisan Water Mixable Oil Color).
Although this type of paint may be thinned with water, artists may prefer to use specially prepared mediums for improved texture and control. These mediums improve flow (i.e., make the thinned paint less runny and more easily controlled) and can slow or speed up drying time. Mediums are offered by many of the paint manufacturers.
Royal Talens also has produced a water mixable painting paste that acts as a thickener as well as transparetizer which will not change the consistency of the paint. There are many documented issues with accelerator products in this category causing cracking and damaging the archivability of the medium.
Winsor and Newton has created a special line of oils, mediums, varnishes, and thinners to complement their “Artisan” brand of water mixable oil colors. This line includes thinner, linseed oil, safflower oil, stand oil, painting medium, fast drying medium, and impasto medium, as well as gloss varnish, matt varnish, satin varnish, and varnish remover.
Daniel Smith also offers a range of suitable mediums.