Acrylic vs. Oil: What Is Inside The Paints

In this series of articles, I’d like to look at these two mediums from a professional and responsible artist’s point of view, thinking about the artwork itself and the impacts that working with these mediums includes. There is no straightforward answer to what’s better and I don’t think such a question can be valid; this article is aimed to make an informed choice for this or that art project. I’ll try to be as straight to the point as possible.

Oil Paints

Historically, oil paints are made from pigment and oil. However, fresh-made paints, especially if they contain mineral pigments, will start separating within a very visible time frame (some paints show separation even after a week from the manufacturing date). Copper Oxide pigments separate in 5-7 days, and earthy pigments, depending on their particle size, within 1-3 months. Organic pigments, due to their lightweight nature, may not show any significant separation even after a year of manufacturing. Pigment use is a separate topic, so I’m not going to pull it here.

As it can take 5 or even more years between manufacturing time and actual purchase and consumption time, manufacturers need to make sure that their paints are still presentable. So, to stabilize paints (depending on pigments) they use wax pastes as well as barium sulfate. To increase the quality of the painting and the elasticity of the film, some resins can be added. Usually, it’s turpentine gum (don’t mix it up with turpentine oil), dammar, mastic etc. To shorten drying time a small amount of turpentine oil may be added.

Some paints, depending on pigments and grade (studio, artist, pro) may have fillers that usually have a mineral nature: kaolin, marble dust, calcite, barite, talc, etc.

Professional paints have pigment, oil, wax, resins and a minimal amount of fillers.

Acrylic paints

Here, everything is much more complicated. Long story short, here is a list of ingredients:

1. Pigment. The same as for oil. The different pigments used for acrylic and oil will be covered in a separate article. 
2. Binder. It’s either acrylic dispersion or emulsion or both. They contain styrene and/or an alkyl methacrylate. The alkyl methacrylates used are methyl methacrylate, isodecyl methacrylate or stearyl methacrylate. Many terms, but all these can be simplified as monomers that form polymers after the carrier (water) evaporates.
3. pH adjuster and dispersant. When we paint in acrylic, we expect that paint will be easily spread, and mixed with other colours. That’s why ammonia is an essential acrylic paint component. Pigments, as we know, are solid particles and tend to settle down on the bottom of the pain container with time. Ammonia helps to disperse the pigments evenly throughout the paint, thereby providing nice consistency and colour uniformity.
4. Surfactant. These chemicals prevent paints from early cracking and provide an even drying process. Here we have ammonia again, glycerine, and propylene glycol.
5. Fungicide. As acrylic has water inside and some organic and inorganic ingredients, paints need to have preservatives that stop mould growth. Here, it can be ammonia, formaldehyde, or petroleum by-products.
6. Paints, that contain mica powder as well as very thick paints may contain solvent to prevent separation and prevent paints from drying in tubes.

Ingredients used in paints deal with safety and health issues.