Another version of optical mixing is to combine pigments onto the canvas without blending, letting the brush create streaks and swirls that retain distinct hues but from further away blur to the eye, and appear as a single hue. This is very common in Old Masters as well as Impressionist works, and besides creating far more interesting textural effects, avoids the novice's tendency to overmix and apply as if "painting a house," where large flat areas just look dull, one dimensional, and lackluster. Paint by Numbers is the worst form of this practice. Classic glazes maximize the brightness of the resulting effective hues, while semi-opaque thin glazes can create very interesting, scintillating effects that otherwise would be only the result of muddying to tertiary intermediate hues. Using overpainting instead of overmixing can give much more interesting results, as long as the underlayer is dry so it does not mix with the next layer. Modern mediums like Liquin greatly facilitate experimentation while reducing the risks from violating old rules about oil painting, thin over fat, etc.
