(Excerpts from ART HARDWARE: The Definitive Guide to Artists’ Materials, by Steven Saitzyk © 1987 revised 1998)
It is easier to learn how to paint with oils than with most other media. At the same time, it is the most difficult of media to master, primarily because it is so versatile. There are so many styles of painting, formulas for media, pigments, and tools in oil painting that many find they do not have the patience necessary to master this medium. There are many quicker, less complicated media of expression, such as acrylic polymer emulsion paints, which have become oils greatest rival today. However, their history is quite brief dating back only to the end of WWII. By convention that small time span would make acrylic emulsion paints still experimental since it has yet to fully stand the test of time. They have been tested under artificial conditions in what are called accelerated ageing tests, and indications are quite good, but it is not the same as real life situations.
Many painters have begun in, or switched to, acrylic because of the lower costs, availability in larger volumes, fast drying, easy clean‑up, absence of hazardous thinners, and minimal-yellowing characteristics. In general, acrylics are primarily used as an alternative to oil, and because they are considered superior. The nature of acrylic emulsion prevents the paint from being made with the same high concentration of pigments as oil paints. Some pigments traditionally used in oil paint are not made into acrylic colors because their unique qualities cannot be seen in a polymer medium. The available color range of acrylics is narrower because many pigments cannot survive the alkalinity or cannot stay in suspension. Manufacturers of acrylics emulsion paints have recently put great effort into expanding their narrow range of available media by adding body and particles to the media, but it is more surface than substance when it is compared to the versatility of oils. Emulsion paints also dry with a much darker appearance than the wet color, which can be deceiving for the beginner. If acrylics were compared to the classification of grade levels used for oils, the finest of them would reach no higher than professional grade. That said, there are painting styles that lend themselves so well to acrylic emulsion paints, where it would be very difficult without scientific testing to see any difference between oils and emulsion paints.
The only other medium that oils have been compared to is the medium I have painted with for many years and that is egg tempera. When used properly, it can be more brilliant, luminous, non-yellowing, and permanent than oils. However, the techniques for egg tempera are even more difficult to master, and it is a far more fragile medium.