Understanding oil painting terms transforms the act of applying pigment into a deliberate dialogue with history and technique. For the working artist, the vocabulary of the medium is not merely academic; it is the functional language of manipulation, describing how a viscous medium behaves on a support and how light interacts with a cured film. This glossary moves beyond simple definitions to explore the practical implications of each term, empowering painters to make informed decisions that directly impact the texture, luminosity, and longevity of their work.
The Language of Consistency and Application
Before color even touches canvas, the artist must contend with the physical behavior of the paint itself. Oil paint exists in a spectrum of states, from stiff peaks to fluid washes, and mastering the vocabulary of consistency is the first step toward control.
Fat Over Lean
The foundational rule of oil painting dictates that each successive layer must contain more oil than the layer beneath it. "Fat" refers to paint with a high ratio of oil to pigment, making it slick, translucent, and slow to dry. "Lean" paint, conversely, has more pigment and less oil, behaving more like tempera and drying quickly. Ignoring this principle risks the cracking of the paint film, as a stiff, dry layer (lean) cannot flex with a soft, flowing top layer (fat).
Mediums and Solvents
To manipulate consistency, artists utilize a specific lexicon of additives. A solvent such as turpentine or mineral spirits reduces the paint's viscosity, making it more "open" (drying slowly) and easier to spread for initial blocking-in. Mediums like linseed oil, walnut oil, or alkyd resins increase the fat content, enhancing gloss and transparency. Liquin Original or Galkyd are examples of modern mediums that accelerate drying while maintaining a buttery texture, bridging the gap between traditional oil and faster-working industrial materials.
The Surface and the Image
Just as language relies on grammar, oil painting relies on the physical interaction between the ground and the image. The terms describing this interaction define the structure of the artwork.
Ground and Underpainting
The ground is the preparatory layer applied to the support—usually canvas, panel, or paper. Traditionally, a white lead ground was standard, but modern acrylic gesso is now ubiquitous. An underpainting is the initial layer of color laid down to establish values and major shapes. Techniques like grisaille (monochromatic underpainting) or verdaccio (green-toned underpainting) are used to build a tonal foundation before color is introduced, effectively mapping the composition before the final color is applied.
Scumbling and Glazing
These are two fundamental methods of layer manipulation. Glazing involves applying a thin, transparent layer of "fat" paint over a dry, "lean" underpainting. This is how artists achieve the deep, jewel-like luminosity characteristic of Old Masters, as the light passes through the transparent color and reflects off the opaque layer below. Scumbling is the opposite: applying a thin, opaque layer of lighter color over a darker dried layer. This technique is excellent for creating atmospheric effects, such as mist or the subtle variation of skin texture, where the underlying tone subtly peeks through the top layer.
The Palette and the Pigment
Color theory in oil painting is governed by the physical properties of the pigments themselves. Knowing the behavior of your colors is essential for mixing and longevity. Hue and Chroma Hue is the color's name on the spectrum—red, blue, or yellow. Chroma, or saturation, refers to the intensity or purity of that hue. High-chroma colors appear vivid and bright, while low-chroma colors appear muted or grayed. Artists must understand that mixing high-chroma pigments often results in a rapid decrease in chroma, requiring careful balancing to achieve the desired subtlety without sacrificing depth.
