There are many in the world of art who believe that oil paintings are superior or somehow worth more than those painted using acrylics. This belief is borne out of the fact that oils have been around longer and are the medium of choice for many well-known professional fine artists. As well, many universities and art schools tout oils as being the best choice for an artist to paint with and incorrectly tell their students that oil paintings have a much longer archival life than acrylics.
However, there is little or no evidence to support any of the above theories. Scientific studies have been conducted on both acrylic and oil in side-by-side comparisons and both fare about the same under a carefully controlled light, temperature and moisture tests.
As well, it has been shown that many oil paintings may fare worse than acrylic since many of the ingredients used are organic and have a decay rate much faster than acrylics which are now made from synthetic polymers.
Many paintings from the 1800s are decaying rapidly and a constant need for restoration has created an entire business revolving around this need. Restorers charge exorbitant fees for their work and rightly so. I can't imagine having to handle a masterwork and recreate sections.
Some would even argue that oils look better "due to that nice sheen they have" but with the advent of acrylic varnishes - both in gloss and matte - that argument doesn't hold much credence.
Much of the current "oils are superior" type of thinking is left over from an earlier era - the 1940s and 1950s - when the first acrylic paints came into use by artists. At that point, acrylics were new and still evolving into the excellent product they are today. Early acrylic paints had a tendency to break down, lose color and even flake off of the canvas or substrate. Many argue that oils carry a heavier pigment load, but my own research has shown that the largest and best acrylic paint manufacturers use the same amount of pigment (and in some cases, more) as oil painting manufacturers. This becomes abundantly clear when the manufacturer produces both types of products. It would be laughable to imagine that they would, for any reason, hold back pigment on their acrylic lines.
I've gone to many galleries where the proprietor announces with much gusto that they only carry oil paintings and refuse to carry acrylic. It always comes as a surprise and, in my opinion, the loss is theirs. Imagine ignoring an entire swath of artists whose works may better the ones they currently carry simply based on what looks, to an informed mind, like superstition.
Talking to artists who work exclusively in oils, one sometimes meets with the same stubborn refusal to budge from their ideologic position. I find it humorous and at the same time somewhat puzzling, mainly because of the constant waiting that an artist goes through when working with oils. For that reason alone, many oil painters will have several paintings in progress at once, which in my opinion, leads to a loss of consistent thought processes that many artists use working on one piece.
Thankfully, there's a new breed of artists who work in both mediums. Many use acrylics for the underpainting but prefer oils for their final layers due to the ability to rework areas and make corrections days later. As well, some artists will work in acrylic only on some works because of the drying time and the ability to layer paint quickly over older layers. Many artists have changed from using oils to using acrylics because of the well-known toxicity of oils and the mediums and thinners used along side them. Most importantly, the toxins in many oil paints and oil-based mediums are not only bad for the environment but bad for we humans as well and can be blamed for headaches, sinus problems and other illnesses including cancers.
In any case, the old "oils are better than acrylics" thinking may still take some time to diminish and fade away altogether. It is my hope that the art-buying public will educate themselves and not be led astray by those galleries and artists who are stubbornly living in the past. Those in the know thankfully realize the truth and because of that fact they are open to an entire bright and colorful world of art created in acrylic or oil or both, depending on their particular bent.
This debate is nearly as old as acrylic paints themselves and you will get various opinions on the subject depending on who you ask, especially artists. Various oil painters will defend oils and acrylic painters will defend acrylics for the most part. I happen to like both, but choose to use acrylics because of health concerns and the fact that they fit my style and process. Each has their own merits and it really comes down to personal taste for the artist using them.
However, the same should never be applied when buying art. I only hope that those of you who actually collect or purchase art will buy it for what you see in the end result, not for what was used to create the work.