Oil paint has a higher pigment load than acrylic paint. As linseed oil contains a smaller molecule than acrylic paint, oil paint is able to absorb substantially more pigment. Oil provides a refractive index that is less clear than acrylic dispersions, which imparts a unique “look and feel” to the resultant paint film. Not all the pigments of oil paints are available in acrylics.
Due to acrylic paint’s more flexible nature and more consistent drying time between layers, an artist does not have to follow the same rules of oil painting, where more medium must be applied to each layer to avoid cracking. It usually takes 15–20 minutes for one to two layers of acrylic paint to dry. Although canvas needs to be properly primed before painting with oil to prevent it from eventually rotting the canvas, acrylic can be safely applied straight to the canvas. The rapid drying of acrylic paint tends to discourage blending of color and use of wet-in-wet technique as in oil painting. Even though acrylic retarders can slow drying time to several hours, it remains a relatively fast-drying medium and adding too much acrylic retarder can prevent the paint from ever drying properly.
Meanwhile, acrylic paint is very elastic, which prevents cracking from occurring. Acrylic paint’s binder is acrylic polymer emulsion – as this binder dries, the paint remains flexible.