Solvent-Free Plein Air Oil Painting: A Practical Guide for UK Artists

You don't need turpentine to paint with oils outdoors. Solvent-free plein air oil painting is genuinely workable, and for many painters it's actually simpler than the solvent-based setup they started with. This guide covers the three main approaches, how to clean your brushes in the field, and a practical session workflow you can follow on your next outing.

What Does Solvent-Free Actually Mean?

Oil paints straight from the tube contain no solvent. The pigment is bound in a drying oil, usually linseed, safflower, or walnut, and that's it. Solvent only enters the process if you add it yourself, typically as a thinner or brush cleaner.

The solvents most painters use are turpentine, white spirit, or low-odour alternatives like Zest-It or Sansodor. They're useful for thinning paint and rinsing brushes, but they're also flammable, smelly, and classified as hazardous liquids. For plein air painting specifically, that creates real inconvenience: open jars outdoors, fumes in a warm car, and restrictions when travelling by train, coach, or plane.

Going solvent-free means replacing those solvents with one of three alternatives:

• Drying oils (walnut, linseed, safflower) used sparingly as a medium
• Solvent-free alkyd gel or fluid mediums (such as Gamblin's range) that speed drying without any hazardous component
• Water-mixable oil paints designed to thin and clean up with water alone

Three Solvent-Free Systems to Choose From

Here's how to think about this. The three systems aren't equally suited to every painter, and you don't need to try all of them. Read through and pick the one that fits how you already work.

Option 1: Just Use a Drying Oil

The simplest approach is to stop adding solvent and use a drying oil instead. Walnut oil is the most commonly recommended choice for plein air work: it's paler than linseed, yellows less over time, and handles well with lighter colours. Linseed oil dries a little faster and gives a more durable film. Safflower dries more slowly, which can be useful for blending but is less practical when you're working in layers outdoors.

The key is restraint. A tiny amount goes a long way, and overloading your paint with oil causes it to stay wet for days and risks long-term film problems. If you already paint with regular oils and want to make the smallest possible change, this is where to start: just swap the solvent jar for a small dropper bottle of walnut oil and see how it feels.

Option 2: A Solvent-Free Gel or Fluid Medium

This is the approach most plein air painters settle on, and it's the one we'd recommend as a default. Alkyd-based solvent-free mediums like Gamblin Solvent-Free Gel and Gamblin Solvent-Free Fluid give you faster drying than plain oils, better paint extension, and support for both texture and glazing work, all without any hazardous liquid in your kit.

These mediums come in compact, leak-proof packaging that travels easily, and a little goes a long way in practice. The critical thing to understand is the 25% rule: because these mediums contain no evaporating component, they're essentially all fat. Using too much causes wrinkling, slow curing, and weak paint films. Keep additions well below a quarter of your total paint mixture, and you'll have no problems.

Gamblin Solvent-Free Mediums

Gamblin : Solvent Free Gel : Oil / Alkyd Painting Medium : 37ml

£6.60 · Jackson's

Gamblin : Solvent Free Fluid Oil / Alkyd Painting Medium : 125ml

£13.50 · Jackson's

Option 3: Water-Mixable Oil Paints

Water-mixable oils (WMO) are a distinct category of oil paint in which the binding oil has been modified to disperse in water. You can thin them with water, blend them with dedicated WMO mediums, and rinse your brushes on site using nothing but water from a bottle. Back home, soap and warm water finishes the job.

This system suits painters who are used to acrylics, or anyone working in a shared house or small studio where even drying-oil smells are unwelcome. The fat-over-lean principle still applies: more water makes a leaner layer, so keep water additions to early stages and use the dedicated medium for later, richer layers.

You don't necessarily need to replace your entire paint collection. A product like Schmincke Medium W can convert regular oil paints into a water-mixable system, though if you're starting fresh, purpose-made ranges like Schmincke Norma Blue or Cobra Artist give you the most consistent results. Both are widely available from UK suppliers.

Water-Mixable Oil Paints

Schmincke : Norma Blue : Water Mixable Oil Paint

£8.20 · Jackson's

Cobra : Artist Watermixable Oil Paint

£5.70 · Jackson's

Solvent-Free Oil Painting Outdoors: Fat-Over-Lean Still Matters

One of the most common questions when switching to solvent-free working is whether the fat-over-lean rule still applies. It does, and it arguably needs more conscious attention than before, because there's no solvent to create a naturally lean first layer.

The principle is straightforward: each successive layer of paint should contain slightly more oil than the one beneath it. A layer that's leaner than the one below it dries faster on the surface while the layer underneath is still moving, which causes cracking over time.

In practice, the solution is simple. Start with paint straight from the tube for your first pass, or with just a touch of oil or gel mixed in. Add a little more medium in subsequent layers, keeping gel and fluid mediums well below the 25% mark at all times.

It's worth noting that solvent-free gels and fluids are for extending paint and supporting texture, not for thinning it to a wash. If you need a very thin, transparent initial layer, applying paint straight from the tube and working quickly is more reliable than trying to make a glaze with gel. For WMO painters, a small amount of water works well for a lean first layer, with the dedicated medium introduced in later stages.

Cleaning Brushes in the Field Without Solvent

Many painters assume they need solvent to clean brushes. You don't. The oil-and-wipe method is genuinely effective, and with a bit of practice it becomes second nature.

A few additional notes worth keeping in mind. Safflower oil is the better choice for the cleaning jar over linseed: it's paler and won't gradually tint your light-coloured bristles yellow with repeated use.

Carry a sealable bag or tin for used oily rags. Oils that are oxidising as they dry can in rare circumstances generate heat in a bundled rag. It's an unlikely hazard outdoors, but don't leave a scrunched pile of oily cloths sitting in a warm kit bag on a sunny day. Lay them flat or seal them in a tin, and deal with them properly at home.

If you're using water-mixable oils, the process is even simpler: rinse brushes in clean water on site, then soap and warm water at home.

What to Pack: A Minimal Solvent-Free Plein Air Kit

The good news is that a solvent-free kit is lighter and less hazardous than a conventional one. Here's what's different versus the standard solvent-based setup:

• Paint: Any professional artist oil paints (they contain no solvent themselves), or water-mixable oils if using that system.
• Medium: A small 37ml tube of Gamblin Solvent-Free Gel or a leak-proof dropper bottle of walnut oil. Not both; keep it simple.
• Brush cleaner: A small lidded jar containing safflower or sunflower oil.
• Rags: Old cotton cloths or paper towels. Bring more than you think you'll need.
• Sealable bag or tin: For used oily rags.
• Panels: Acrylic-gessoed panels or canvas boards work well. Tone them at home with diluted acrylic, not a solvent wash on location.
• Palette knife: Useful for scraping back unwanted paint rather than dissolving it with solvent.

Drying oils for plein air use

M. Graham : Artist's Oil Medium : 118ml : Walnut Oil Medium

£14.70 · Jackson's

Natural Earth Paint : Walnut Oil (Refined) : 237ml

£14.20 · Jackson's

M. Graham Walnut Oil is well-regarded amongst oil painters and widely available from UK suppliers. Natural Earth Paint's refined walnut oil is a sound alternative, particularly if you get through a fair amount. Either works well in the field; use them sparingly and you'll find a small bottle lasts a good number of sessions.

A Note on "Non-Toxic": What It Does and Doesn't Mean

Removing solvents from your painting practice genuinely reduces your exposure to volatile organic compounds (VOCs). Turpentine and mineral spirits release fumes that can cause headaches, dizziness, and respiratory irritation with regular exposure. Eliminating them is a meaningful safety improvement, not a marginal one.

That said, "non-toxic" is a term that needs some qualification. The oil paints themselves are not without hazard: some pigments, including certain cadmiums and cobalts, require basic care. Wash your hands after every session, avoid touching your face while painting, and don't eat while you work. Pigment safety is a separate matter from solvent safety, and switching to solvent-free mediums doesn't change the picture there.

The oily rag point bears repeating here too. Drying oils oxidise as they cure, and this process releases a small amount of heat. In normal outdoor conditions this is barely relevant, but a thick bundle of oil-soaked rags left in a warm enclosed space is worth treating with the same common sense you'd apply to any flammable material. Spread them flat to dry or store them in a sealed tin.

Solvent-free products do avoid petroleum distillates, and that's genuinely better for both the painter and the environment. Just don't read "solvent-free" as "completely safe without any precautions." Safer, yes. Worth doing, absolutely. But still basic care required.

Solvent-Free Oils and UK Travel: What You Need to Know

Turpentine and white spirit are classified as flammable liquids, which creates real complications when travelling. Most UK airlines and many ferry operators restrict or prohibit them in hold and cabin luggage, and even coach operators sometimes flag them. In practice, many plein air painters simply avoid travelling with solvents altogether.

Solvent-free alternatives are far more convenient:

• Gamblin Solvent-Free Gel comes in a toothpaste-style tube or small bottle, with no flammability classification.
• Drying oils in small dropper bottles are similarly straightforward to carry.
• WMO painters travelling by air need only water on location, making their kit the most streamlined of all.

Always check with your specific carrier before flying. Regulations vary between airlines and can change, so a quick check before you pack is worth the two minutes it takes.

Getting the Most from Solvent-Free Oil Painting Outdoors

If you're switching from solvent-based working and want to ease in gently, the simplest first step is just to stop adding solvent. Replace it with a touch of walnut or linseed oil and try one session like that before you invest in anything new. Many painters find they need far less than they expected.

If you'd rather have better handling and faster drying from day one, Gamblin Solvent-Free Gel in the 37ml tube is a practical starting point for plein air specifically. It's compact, it travels easily, and because you use it sparingly, a small tube goes a long way.

If brush cleaning was your main reason for keeping solvent in the kit, give the oil-and-soap method a proper run of three or four sessions before deciding it doesn't work. The technique takes a little adjustment but it genuinely cleans brushes well, and most painters who stick with it don't go back.

Painting outdoors without solvents is not a compromise. It's a lighter kit, a less hazardous setup, and for many painters a simpler workflow. The paintings look the same. The experience is better.