Oil washes are a favourite of vehicle and armour painters because they're incredibly forgiving. Unlike acrylic washes, oil stays workable for a long time, so you can apply it generously, then wipe it away from the areas you want clean. The result is crisp, dark recesses and smooth, clean panels with natural-looking transitions.
What you need
- Artist oil paint in a dark colour (black, dark brown or a mix)
- Odourless mineral spirits or a similar low-odour thinner
- Gloss varnish and matt varnish
- A cheap brush reserved for oils (don't use your good acrylic brushes)
- Cotton buds, make-up sponges or small squares of paper towel for wiping
- A non-porous palette: a ceramic tile or metal tin lid
Safety first
Even "odourless" thinners give off fumes. Work in a well-ventilated room, keep the lid on the thinner when you're not using it, and consider gloves. Rags and paper towel soaked in oil and solvent should be laid flat to dry outside, or stored in a sealed metal or glass container, before disposal. Keep everything away from children and pets.
Step 1: Paint and let it cure
Paint the model in acrylics as normal, but leave out the metallics if you plan to varnish (more on that below). Let the acrylic dry completely, ideally overnight.
Step 2: Gloss varnish
This is the step people skip, and it's the one that matters most. A matt surface is microscopically rough, so the oil clings to it everywhere and stains. A gloss surface is smooth, so the wash flows into recesses and wipes cleanly off raised areas. Varnishing also protects your acrylic layer: the thinner won't dissolve acrylic, but the friction of wiping can rub unprotected paint away.
Apply one thin, even coat of gloss varnish and let it dry fully.
Step 3: Mix the wash
Squeeze a small amount of oil paint onto your palette. Many painters first leave it on a scrap of card for a short while to soak up some of the excess oil, which helps it dry faster and more matt. Then add thinner a little at a time until you have a fluid, ink-like wash. Too thick and it won't flow; too thin and it can go grainy or blotchy.
Pure black can be harsh. A dark brown, or black mixed with brown, often looks more natural on lighter colours.
Step 4: Apply
You have two options:
- Pin wash: touch the brush tip into panel lines, around rivets and into recesses. Capillary action pulls the wash along the line. Neat and precise.
- All-over wash: brush the wash generously over the whole area. Quicker, and it adds an overall tone.
Step 5: Wipe off
Let the thinner evaporate until the wash looks less shiny, usually somewhere between 15 minutes and an hour depending on the paint and thinner. Then gently wipe the raised surfaces with a clean bud, sponge or paper towel, wiping downwards, the way rain streaks would run. Dampen the wiping tool with a little thinner to remove more; use it dry to remove less.
Wipe gently. You're lifting oil off a smooth gloss surface, not scrubbing. If you remove too much, just apply more wash. If it's dried too far, a brush dampened with thinner will reactivate it.
Step 6: Dry and seal
Oil paint can be touch-dry in a few hours but takes much longer to cure fully. A warm, dry room or a gentle stream of warm air speeds it up. Once it's dry, apply matt varnish to remove the gloss and lock everything in. You can then add metallics, final highlights and details in acrylic on top.
Why metallics go last
Matt varnish dulls metallic paints dramatically. Paint your metals after the final matt coat, or mask them before varnishing.
Beyond panel lines
- Streaking: dot oil paint below rivets and drag it downwards with a thinner-damp brush for rain marks.
- Grime and dust: brown and ochre oils blended onto lower areas of vehicles.
- Metal tones: a black or dark brown oil over silver gives a convincing oily, mechanical look. It works especially well on robotic armies; see our Necrons guide.
- Smooth gradients: because oils stay workable, they blend beautifully. This is useful for reflective effects like non-metallic metal.
Troubleshooting
- Stains on flat areas: the surface wasn't glossy enough. Add another gloss coat next time.
- Grainy finish: the wash was over-thinned or the paint wasn't mixed well. Use more paint and less thinner.
- Acrylic rubbed off: varnish before you wipe.
- Still tacky after days: the oil was too rich. Blot it on card before mixing next time.
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