Water miscible oil paint 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
Gum arabic insoluble in water upon exposure to ultraviolet light. In the final print, the acacia gum permanently binds the pigments onto the paper. Gum arabic is also used to protect and etch an image in lithographic processes, both from traditional stones and aluminum plates. In lithography, gum by itself may be used to etch very light tones, such as those made with a number five crayon. Phosphoric, nitric or tannic acid is added in varying concentrations to the acacia gum to etch the darker tones up to dark blacks. The etching process creates a gum adsorb layer within the matrix that