Underpainting With Oil Paints

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A thin oil underpainting on Wallis paper.

Starting pastel paintings with a thin, wet, loose underpainting is something many artists enjoy. It sets up a foundation on which to respond with the subsequent application of pastel. Though not meant to be the finished painting, the underpainting often plays a major part in the final appearance. Depending on the medium used and the surface it applied to, it can have a variety of appearances.

Personally I have utilized some form of underpainting from the earliest years of my painting adventure. Over those years, I have experimented with a variety of surfaces and media. Thin watercolor and oil washes have becoming two of my favorites. Two things need to be analyzed when choosing your means of underpainting: how the medium will respond to the surface: and how it will interact with the pastel. Do a little research and experimentation on your own before committing major efforts to a procedure that may prove to be non-archival.

What lead me to experiment with very thin washes of oil paint was the introduction of acrylic-based sizing and binders in the manufacture of pastel surfaces. These allow for no migration of upper layers to the substrate surface below: in essence, isolating it from any harmful chemical interaction. Papers such as Wallis sanded paper even state that they accept oil paint. I don’t advocate thick applications of oil. Besides taking a major amount of time to dry, it would introduce a considerable amount of oil (commonly linseed oil) that could negatively interact with the pastel. My working procedure is to thin the oil colors to the consistency of weak tea using a highly refined mineral spirit like Gamsol by Gamblin, or Turpenoid by Weber. I apply these very thin washes with a brush, allowing them to run and interact to produce an interesting underpainting (see the example above). This is merely a stain and I can’t stress enough how thin it must be!

After the mineral spirits evaporate, which happens very quickly, pastel can then be applied. You may ask: why oil? Why not just use pastel spread with mineral spirits? The reason is ease of application. I can better control the placement of color and bleeding of the colors with tiny amounts of oil paint mixed and made wet on a separate palette. Pastel made wet on the painting surface is much more unruly. It’s nearly  impossible to tell the two apart, much like a watercolor underpainting compared to wet pastel. Since many pastel artists work in other wet media, they are often more comfortable getting a painterly underpainting by applying the initial color with a brush, but it really is just a matter of personal choice.

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2 thoughts on “Underpainting With Oil Paints

  1. Richard McKinley

    Jeanne, The issue with acrylic is its ability to create a plastic film. Acrylic paints are polymer (plastic) based and capable of leaving behind a thin film that easily resists pastel. If extremely thinned it is capable of working on some porous surfaces. Due to its rapid drying time any thick applications can not be thinned later creating areas that wont accept pastel well. Watercolor, gouache and other water-based mediums do not dry permanent, and are there for rewet-able. If very thin oil paint is used (as described above) and becomes a little thick, it can be thinned with more mineral spirits, as it dries slowly. My best advice is to experiment and see what works best for you. Everything discussed has come from years of trial and error.

    Glad the blog is providing information and motivation. Pastel is a wonderful medium, enjoy!

  2. Jeanne Guerin-Daley

    How about using thin washes of acrylic paint as an underpainting? How would that compare with watercolor? Is there a reason you don’t mention that?

    Also, thank you for all your posts. As someone who only recently discovered the joy of using pastels, I am very interested in exploring the possibilities of the medium, and your advice has taught me so much in such little time!

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