Choosing Painting Mediums: A Focus on Working Properties

Throughout the years of consulting with oil painters and answering their technical questions, the subject of painting mediums has dominated our interactions. Understanding painting mediums can seem like a lifelong pursuit. This newsletter aims to take some of the guess work out of choosing the right painting medium by focusing on your own artistic intentions.

Oil painting mediums are simple. Mediums make oil colors thinner, thicker, glossy, or matte. Mediums can either speed up or slow down the drying time of oil colors. These are the working properties that Robert Gamblin focused on when he developed the array of Gamblin painting mediums. By focusing on working properties rather than ingredients, we can liberate painters from their reliance on toxic turpentine and old concoctions that make paintings darken and crack as they age. In consulting with painters who want to give up mediums that contain strong solvents, we ask “what does your medium do?” rather than “what is in it?”

All painting mediums can be placed into two groups: fluids and gels. Fluid mediums can be split into two categories: low viscosity and high viscosity. “Viscosity” refers to a material’s resistance to movement. Low- viscosity materials are very fluid, like water, whereas high- viscosity materials are thicker, like molasses. These two groups of fluid mediums have very different effects on paint layers.

Low-viscosity fluid mediums are great for creating thin washes of color, especially for underpainting techniques. When a moderate amount of low-viscosity fluid medium is added to oil colors, they retain the brush marks as the paint layers dry. The slowest-drying versions of low-viscosity mediums are simple mixtures of one part linseed or poppy oil mixed with an equal amount of Gamsol OMS. Gamblin Galkyd Slow Dry will allow painters to work wet into wet for approximately 24 hours. Galkyd Lite is a fast-drying, low-viscosity medium.

High-viscosity fluid mediums create self-leveling effects, giving the oil colors an enamel-like quality. A mixture of one part Stand Oil and one part Gamsol OMS would create a slow-drying, high-viscosity medium. Gamblin Galkyd is a fast-drying, high-viscosity painting medium. Galkyd is excellent for glazing techniques, as thin layers dry within 18 hours. TIP: Galkyd is the fastest-drying Gamblin medium. As an economic concern, consider adding a small amount of Gamsol to the Galkyd periodically to prevent the medium from drying in the bottle.

Gel painting mediums extend oil colors without making them fluid. They are useful in painting techniques where defined brushwork is desired. Neo Megilp is a soft gel medium which imparts a silky smoothness to the oil color. As a glazing medium, Neo Megilp adds “body,” which means your glaze will be thicker. You can add a thin layer to your canvas and then paint color into the medium. This was Turner’s technique for creating atmospheric glazes. Neo Megilp is moderate to slow in its dry time as compared to the other Gamblin mediums.

If Neo Megilp is a soft, slower-drying gel, Galkyd G-Gel is a stiffer, faster-drying gel medium. G-Gel is formulated for painters who want to create transparent impasto layers that hold brush marks. G-Gel makes impasto of approximately 1/4" thick.