2.2 Painting Media & Methods

Painting Media & Methods

Painting is a deeply chemical process. Understanding the behavior of paint requires recognizing its three universal components: pigment (the dry powder that provides color, derived from minerals, organics, or synthetic chemicals), the binder (the substance that holds the pigment particles together and adheres them to the surface), and the solvent or vehicle (the liquid that thins the paint and alters its viscosity). The type of binder used defines the medium and dictates the artist's working methods, drying times, and preservation requirements.

Oil Painting

Oil painting, popularized in the Northern Renaissance by artists like Jan van Eyck, revolutionized art due to its versatility and depth.

Chemistry and Application

The primary binder in oil paint is a drying oil, most commonly linseed oil (though walnut or poppy oil are used for lighter colors to prevent yellowing). Oil paint is thinned with solvents like turpentine or mineral spirits. Unlike water-based media, oil paint does not dry through evaporation. Instead, it cures through oxidation, a chemical reaction where the oil absorbs oxygen from the air and hardens. This process is remarkably slow, allowing artists days or weeks to blend colors, create soft transitions (sfumato), and rework areas.

Oil Techniques

• Glazing: Applying multiple thin, transparent layers of paint over a dry, opaque underpainting. Light passes through the glazes and reflects off the opaque layer, creating a luminous, stained-glass effect.
• Impasto: Applying paint so thickly that the physical texture of the brush or palette knife stands out from the canvas. It adds tactile dimensionality to the work.
• Alla Prima: Also known as 'wet-on-wet', this technique involves finishing a painting in a single sitting while the paint is still wet, rather than building it up in dried layers.
• Fat Over Lean: A critical rule in oil painting. Each successive layer of paint must have more oil (fat) and less solvent (lean) than the layer beneath it. If a lean, fast-drying layer is painted over a fat, slow-drying layer, the surface will crack as the lower layer shifts during oxidation.

Acrylic Painting

Developed in the mid-20th century, acrylics offer a modern alternative to oils. The pigment is suspended in an acrylic polymer emulsion (liquid plastic). The vehicle is water. As the water evaporates, the polymer particles fuse together (polymerization), creating a continuous, flexible, water-resistant plastic film.

Acrylics dry incredibly fast—often in minutes. This rapid drying time is excellent for artists who work quickly and build many layers in a single session, but it makes smooth, slow blending difficult. Retarding mediums can be added to slow the drying time. Because they are essentially liquid plastic, acrylics can be applied to almost any non-oily surface without the need for sizing, and they are immune to the cracking issues that plague improperly layered oil paintings.

Watercolor and Gouache

Watercolor and gouache are aqueous media where the binder is gum arabic, a natural resin harvested from acacia trees. The solvent is water.

Traditional watercolor is transparent. The white of the paper serves as the primary light source; artists build up darker values by layering washes. Once applied and dried, watercolor can be easily reactivated with a wet brush.

Gouache is effectively opaque watercolor. It contains the same gum arabic binder, but inert white pigments (like precipitated chalk) are added to the formulation. This allows gouache to dry to a flat, matte, fully opaque finish. Artists can paint light colors over dark colors in gouache, a technique impossible in transparent watercolor.

Tempera and Encaustic

Before the dominance of oils, tempera and encaustic were standard mediums.

• Egg Tempera: Uses egg yolk as the binder. It is thinned with water and applied in tiny, cross-hatched strokes on rigid panels (usually coated in gesso). It dries almost immediately to a hard, matte finish. Because it lacks flexibility, it will crack if painted on a flexible canvas.
• Encaustic: An ancient technique (famous for the Fayum mummy portraits) where pigment is suspended in a binder of hot beeswax and damar resin. The artist must paint while the wax is liquid on a heated palette. Each new layer must be fused to the layer beneath using a heat gun or torch. Encaustic is highly durable and completely impervious to moisture.

Fresco

Fresco is a mural painting technique intimately tied to architecture.

• Buon Fresco (True Fresco): Pigment mixed only with water is applied directly to a freshly laid, wet lime plaster wall. As the plaster cures, it reacts with carbon dioxide in the air to form calcium carbonate. The pigment becomes physically locked into the crystalline structure of the wall. It is permanent but requires artists to work in small, daily sections called giornate before the plaster dries.
• Fresco Secco (Dry Fresco): Painting on a completely dry plaster wall. Because the wall cannot absorb the pigment chemically, the artist must use a binder (like egg tempera or glue). Fresco secco is far less durable than buon fresco and is prone to flaking off over centuries (e.g., Leonardo's The Last Supper).