Short answer: Priming (undercoating) is a thin base layer you apply to a bare miniature before painting. It does two things at once: it lets paint grip the plastic, resin or metal chemically, and it creates a slightly rough “tooth” for colour to sit on. That is why it is the first step of any serious paint job; skip it and your paint scratches and flakes off.
So let us walk through that step properly. This guide pulls together primer types, colour strategy and how to avoid classic traps like frosting. If you are just starting out, begin here; if you are advanced, it still helps you sharpen your technique.
What is priming and why does it matter?
At its simplest, priming (undercoating) is a thin, adhesive base layer you apply before you paint. It does two core jobs. First, it lets acrylic paint grip the surface chemically. That matters because if you paint a miniature without primer, you can scratch the dried paint off with a fingernail, or watch it flake while you handle the model.
Second, primer leaves behind a slightly rough “tooth” (the micro-texture paint clings to). Paint settles into that tooth instead of running, forming a clean film. There is a bonus too: it unifies every part into a single colour, so your eye reads the sculpt clearly and you can see where light and shadow belong. Once your prep work is done (for cleaning parts, see Cleaning, Mold Lines & Degreasing) it is time to prime.
Spray, brush or airbrush: which primer type?
All three primers do the same job, but which one you choose changes both the result and how practical it is. Let us look closely at the three main routes in front of you.
- Spray primer (rattle can): The most common and fastest route. Options include Citadel Chaos Black / Corax White / Grey Seer / Wraithbone, Army Painter Colour Primer, Vallejo, Tamiya Surface Primer and Stynylrez. The upside is speed and a smooth thin coat. The downside is that it is sensitive to air and humidity, and sprayed from too far away it leaves a chalky, frosted surface.
- Brush-on primer: Primers like Vallejo Surface Primer and Stynylrez can also go on with a brush. This is ideal for places where you cannot spray (a flat, winter, poor ventilation). The one rule is to apply thin, patient coats so you do not leave brush marks.
- Airbrush primer: This gives the smoothest, most controlled result. Airbrush-ready primers like Stynylrez, Vallejo Surface Primer and Badger spray straight through. It is the best for thin coats, full coverage and detail preservation; the trade-off is the equipment and a bit of a learning curve.
Let us also bust a common myth: “you cannot paint without a spray can” is simply not true. If you live in a flat or fight bad ventilation, brush or airbrush primer is a fully valid and often cleaner path.
Which primer colour should you choose?
Primer colour directly shapes your final scheme, so a random choice can cost you hours later. The logic to keep in mind is simple: a dark primer manages shadow, a light primer manages brightness.
- Black: For dark schemes, metal-heavy models and anyone after deep shadow. It steers you from dark to light and gives automatic shading; but it dulls bright colours and demands more coats.
- White: Essential for bright colours like yellow, red and orange, and especially for Contrast/Speedpaint paints (fast paints that build volume in a single coat). It makes colours glow, but it forgives nothing; every flaw stays visible.
- Grey (Grey Seer / neutral grey): The balance of the two. It gives both brightness and a touch of shadow; it is the safest starting point and the base Games Workshop recommends for Contrast.
- Coloured / brown / bone: Wraithbone (a bone beige) is a warm base for Contrast and saves time on leather, wood and natural tones. For single-colour army schemes, a primer in that colour (e.g. Macragge Blue, Mephiston Red, Death Guard Green) doubles as both primer and basecoat, merging two steps into one.
To go deeper on colour choice, read Undercoat Colour Strategy; to turn priming into a light-and-shadow tool, jump to Zenithal Priming.
How do you spray prime, step by step?
Since spraying is the most common route, the technique is worth getting right from the start. Three things decide the result: temperature, distance and coat count. Let us take them in order.
- Air and humidity: The ideal range is 15–25°C with low humidity. In cold or damp air the spray frosts (dries into a white powder) and the primer will not hold.
- Shake: Shake the can hard for at least 1–2 minutes. Once the mixing ball inside starts to rattle, keep going a little longer.
- Distance: Hold the model roughly 15–25 cm from the can. Too close means you drown the detail; too far gives a gritty surface.
- Coats: Apply several thin “dust” coats from different angles instead of one thick layer. As you do, rotate the model; a painting handle makes this far easier.
- Test: Spray onto card or a plastic spoon first to confirm the can sprays evenly and is not spitting.
If the model is prepped, priming takes only minutes; drying then runs from 30 minutes to a few hours. Always make sure it is fully cured before you paint over it.
The most common mistakes
Priming looks easy, yet this is exactly where most models get ruined. So steer clear of these classic slips.
- Spraying too thick: It swallows detail; faces, fingers and fine text are the first to drown.
- Spraying in damp or cold air: You get a chalky, non-stick frosted surface. The fix is a dry, warm environment.
- Painting before the primer cures: Top coats will not bond and will flake later.
- Wrong primer colour: Black primer under yellow is a nightmare; you will pile on coat after coat just to get saturation.
- Spraying without shaking: You get an uneven, coarse, speckled finish.
Pro tips
Once the basics are solid, a few small habits push your priming to an advanced level.
- If you cannot spray, do not worry; brush or airbrush primer is fully legitimate and often works cleaner in a flat.
- On metal models primer does one extra job: it protects against corrosion and against paint sliding off the bare metal.
- Zenithal priming is an advanced version of this step that adds shadow and light from the very start; glaze (a thin transparent layer) or Contrast over it to pull volume out fast.
- If you are heading straight into basecoats (your first solid colour layer), Basecoating and Contrast & Speedpaint Systems are the natural next reads.
The golden rule the hobby community repeats is blunt: no serious miniature gets painted without primer. Primer is not just a “pre-step”; it is the foundation that decides the longevity and clarity of every layer above it.
Frequently Asked Questions
Is primer really necessary, or can I skip it?
In practice, it is necessary. Paint over bare plastic or resin and the acrylic cannot grip chemically; once dry it scratches off with a nail, flakes while you handle it, and never forms a clean film over fine detail. In short, primer is the single layer that guarantees the longevity of everything you paint above it.
Should I use black or white primer?
It depends on your scheme. Pick black for dark, metal-heavy models where you want deep shadow; pick white for bright colours like yellow, red and orange and for Contrast/Speedpaint paints. If you are unsure, grey (Grey Seer) is the safest middle ground, because it gives both brightness and a hint of shadow.
Why is my primer coming out chalky or white (frosting)?
The cause is almost always the air. In cold or humid conditions, or when you spray from too far, the spray dries before it reaches the surface and leaves a powdery film. The fix is simple: spray in a dry room at 15–25°C, hold the can 15–25 cm from the model, apply thin coats, and shake the can well first.
Can I prime with a brush only, no spray?
Yes, and it is a fully valid method. Primers like Vallejo Surface Primer and Stynylrez brush on well. It is ideal in a flat, in winter, or with poor ventilation. The only trick is applying thin, careful, patient coats so you do not leave brush marks or pooling.
How long should I wait after priming?
Usually 30 minutes to a few hours is enough. Temperature and humidity shift the time, so wait longer when it is cold. Rush and paint over a half-cured primer and the top coats will not bond properly and may flake later. To be sure, hold it under light and check that no wet sheen remains.
Is one primer enough for everything?
A neutral grey primer handles most jobs and is the safest start. Even so, white or Wraithbone for Contrast/Speedpaint, and black for deep shadow, make a real difference. For single-colour armies, a primer in that colour (e.g. Macragge Blue) merges two steps into one by acting as primer and basecoat at once.
Key takeaway and next step
To sum it up in one line: a primer of the right colour, applied thin and fully cured, locks in the foundation of everything you paint; a badly applied one ruins the model from the very start. Get temperature, distance and coat count right and the rest comes easy.
So, are you looking for the right spray, brush primer or airbrush supplies for undercoating? Terminal Wargaming has the paints, brushes & hobby supplies you need.