Oil painting mediums explained: what they do and when to use them

Oil painting mediums are one of the aspects of the medium that confuses beginners most. You can paint perfectly well with oil paint straight from the tube — but mediums open up a significant range of additional possibilities: controlling drying time, adjusting consistency, achieving specific surface qualities, and making certain techniques considerably easier.

First: the difference between solvents and mediums

Solvents — turpentine, mineral spirit, Zest-It — thin paint and clean brushes. They evaporate completely as the paint dries, leaving no residue. Used alone in small amounts for early lean layers, they are perfectly acceptable.

Mediums modify paint handling properties beyond simple thinning. They typically contain oil, resin, or both, and remain in the paint film when dry. The right medium depends entirely on what you want the paint to do.

Linseed oil

Linseed oil is the most traditional and widely used oil painting medium. Adding it to paint increases flow and transparency, slows drying time, and produces a slightly glossier finish. A small amount added to stiff paint makes it more fluid and easier to brush out smoothly.

Cold-pressed linseed oil — the type used by Wallace Seymour in their oil paints — is the highest quality variety: lighter in colour, more free-flowing, and considered to produce a more stable dried film than heat-processed alternatives.

When to use it: when you want to increase fluidity and transparency, slow drying time, or enrich surface quality in later layers. Add small amounts only — too much oil risks wrinkling and long-term instability.

Stand oil

Stand oil is linseed oil heated and thickened to a honey-like consistency. Paint mixed with stand oil tends to self-level as it dries, reducing visible brushmarks and producing a very smooth, enamel-like surface. It dries to a tougher, more flexible film than raw linseed and yellows less.

When to use it: for glazing, for achieving a very smooth painted surface, and in final layers where you want maximum durability and minimum yellowing.

Alkyd mediums

Alkyd mediums are synthetic resin mediums that dramatically speed up drying time — a thin layer can be touch-dry overnight rather than in two or three days. The most widely known is Liquin by Winsor & Newton. They also increase transparency and flow, making them useful for glazing.

For beginners particularly, alkyd mediums can be transformative. Being able to work over a previous layer the next day rather than waiting several days makes the painting process feel considerably more manageable.

When to use it: whenever faster drying is useful — which for most beginners is most of the time. Particularly good for underpainting, building up layers quickly, and glazing.

Wallace Seymour Fast Drying Oil Glaze Medium

This is the medium we most commonly recommend alongside Wallace Seymour oil paints at Craft and Canvas. Because Wallace Seymour oils are made without added driers, drying times naturally vary across the palette. The Fast Drying Oil Glaze Medium, added at 10 to 20%, brings drying times into balance and adds a beautiful depth and translucency to the paint. It works particularly well for glazing and for painters who want more predictable drying times.

When to use it: with Wallace Seymour oils throughout the painting process, specifically when glazing, balancing drying times, or increasing the translucency of a colour.

Impasto mediums

Impasto mediums are thick gels added to oil paint to increase its volume and body without diluting the colour. They allow paint to be built up into heavy, sculptural textures — raised brushmarks, palette knife passages — that retain their three-dimensional quality as they dry.

When to use it: for texture work, expressive palette knife painting, and any technique where physical surface quality is part of the intention.

Varnish

Varnish is applied to the finished, fully cured painting. It protects the paint surface from dust, atmospheric pollutants, and physical damage, and unifies the surface sheen. A removable, non-yellowing varnish is strongly recommended — it can be taken off and replaced if the painting is cleaned in future. Apply only when the painting is fully cured — typically six months to a year after completion for thickly painted work.

Frequently asked questions about oil painting mediums

Do I need to use a medium at all? No — oil paint can be used straight from the tube. Mediums become useful as your practice develops and you want more control. Starting without mediums and introducing them one at a time as you identify a specific need is a perfectly sensible approach.

How much medium should I add? Less than you think. A small amount — typically 10 to 20% of the paint volume — is sufficient. Too much medium weakens the paint film.

What is the best medium for a complete beginner? An alkyd medium such as Wallace Seymour Fast Drying Oil Glaze Medium or Liquin is the most immediately useful, because it solves the most common frustration — slow drying — while also improving the flow and transparency of the paint.

Can I use linseed oil from the kitchen? No. Food-grade linseed oil (flaxseed oil) will not dry correctly in a paint film. Always use artist-grade linseed oil specifically formulated for oil painting.

Shop oil painting mediums and varnishes and the full Wallace Seymour range at Craft and Canvas, Hebden Bridge.