Rules for Permanent Painting

Underpainting, Mediums, and Varnishing

Oil painting is a dialogue between intention and material. Each decision; every pigment chosen, every medium applied, shapes not only the immediate appearance but the long-term life of the work. Understanding how paint behaves beneath the surface is as crucial as the brushwork itself, and nowhere is this more evident than in the underpainting.

Underpainting

The underpainting is the skeleton of a painting, the first sketch in colour. It establishes tone, form, and rhythm, quietly guiding every subsequent layer. For this stage, slow-drying oils are best avoided. If the lower layers remain mobile while the upper layers begin to set, the surface is stressed, often leading to cracking or subtle shifts that betray the artist’s hand. Pigments such as Cadmiums, Ivory and Lamp Black, Zinc White, and Arylide Yellow are particularly prone to slow drying or weak film formation and are therefore better reserved for later passages.
Underpainting colours are typically thinned to encourage fluidity and rapid application. Yet thinning with solvent alone is a common misstep: without sufficient binding oil, the layer may remain underbound, prone to cracking or dusting. A lean oil medium, therefore, is essential to ensure cohesion, permanence, and a reliable foundation for subsequent layers.

Oil Mediums

The use of oil mediums has long been a balance between expedience and longevity. History is filled with experimental recipes and “secret” concoctions, many of which offer brilliance in the short term but instability over decades. Modern formulations, however, provide stability, permanence, and predictability that earlier artists could scarcely imagine. Even so, restraint remains key: the smallest effective amount of medium should always be used.
All permanent oil mediums contain drying oils; linseed, walnut, poppy, safflower, stand, are responsible for binding pigments but also for eventual yellowing or darkening. Non-yellowing oils, such as Stand Oil, are therefore preferred for critical work. The vast majority of Langridge’s range of mediums are based on Stand Oil, produced by heating linseed oil to 575°F in the absence of oxygen. This process polymerises the oil, producing a viscous, stable medium with excellent non-yellowing properties.

Practical Application

Begin with the underpainting using Low Toxic Underpainting or Underpainting Medium. Lean and responsive, it allows confident, rapid application while ensuring that colours dry evenly without sinking in or dulling. Once the underpainting has set, the choice of medium depends on the effect desired.
Low Toxic Paint Medium and Painting Medium improve flow and handling, making them ideal for work completed in one or two sessions. Its tactile “grab” allows wet-into-wet techniques with control and precision. Oleogel, Glaze Medium and Oil Glazing Gel, on the other hand, are designed for subtle spatial effects. By increasing transparency, they allow delicate modulation of existing layers, creating gentle gradations of light and shade without disturbing the underlying structure.
Cold Wax Medium, Wax Painting Paste and Impasto Medium are reserved for impasto or areas where bulk is desired. Silica and wax content imparts a naturally matt surface, increasing body without sacrificing opacity. They are far preferable to gelled oil mediums, which can yellow over time and exhibit surface irregularities.

Varnishing

A final varnish is the protective seal on a finished painting, but it is not a step to be rushed. Oil paint dries by absorbing oxygen; the process can take six months or more, depending on the thickness of the paint. Applying a final picture varnish too soon will impede the natural curing of the paint. For temporary protection during drying, Retouch Varnish may be applied.
Picture varnishes should always be removable. Over time, varnishes collect dust and discolour, and the ability to replace them without damaging the painting is essential. Oil-based varnishes, which cannot be safely removed, are therefore unsuitable as final coatings.

The careful combination of appropriate pigments, lean and considered mediums, and patient varnishing ensures that a painting not only achieves its intended visual effect but endures with integrity.