Short answer: Painting gems and lenses is how you make small round surfaces on a model — power stones, crystals, robot or vehicle lenses — read as glossy, light-catching glass. The trick is to fake three things at once: dark depth on one side, a gradient brightening on the other, and a single sharp white dot on the dark side. Then you gloss it. The result is a technique with a huge effect-to-effort ratio.
In this guide you will see, step by step, how to turn one tiny surface into a gem that makes people lean in. It looks like a mid-level job, but once the logic clicks a single gem takes only minutes. Below you will find the formula, the steps, the paints and brushes, the common mistakes, and a set of frequently asked questions.
What is it and what is it for?
Let us start with the basics. Painting gems and lenses is the technique of making semi-spherical or rounded surfaces on a miniature look like a deep, glowing stone or piece of glass. Power stones, crystals, goggle lenses, robotic eyes and vehicle lenses are the classic targets.
The best part is this: an illusion you build on a tiny area gives a payoff far out of proportion to its size. Paint a two-millimetre stone correctly and the eye locks straight onto it. And because the technique is relatively easy to learn, the result still looks like a professional's touch.
How does it work?
To understand why this works, look at a real surface for a moment. A real glass or gem carries three things at once: one side is dark (shadow and inner depth), the opposite side is light (where light passes through), and there is a sharp glint on top. That glint is called the specular highlight — the brightest reflection on the surface. Mimic that trio and the brain reads the surface as glossy glass automatically.
Some painters have boiled this logic down into a formula. The classic one, passed around the Creative Twilight and Hellfire Hobbies circles, goes like this: dark base, a gradient that brightens in steps, a single white reflection dot, and finally a glossy varnish. The gloss (something like Citadel 'Ardcoat) is the last but non-negotiable part, because it physically shines the surface and completes the illusion even in photos.
As Hellfire Hobbies puts it: "Finally, we place a white dot toward the dark area of the lens. This is what gives the lens its glass look; it simulates the reflection."
How do you do it step by step?
Now let us turn the theory into practice. The sequence below is for a red gem, but the same logic works in any colour. The key is not to rush — let each layer dry before you move on to the next.
- Dark base: First, paint the whole gem a dark colour (for red, a deep red or maroon). This base gives both the depth and the starting point of the gradient.
- Gradient: Next, brighten one half of the gem (usually the bottom, the lit side) in steps. Think 3–4 layers: dark red, red, orange-red, and an almost-white bottom edge. Keep the top half dark, because that is the inner depth.
- Smooth the transition: If your layers leave visible steps, erase them with layering and glazing. A smooth gradient is exactly what separates a gem from a crude rock.
- Reflection dot: Now place a single, small, pure white dot on the dark (top) side. The logic is simple: light comes from above, so the glint sits high, while the gradient brightens low. That contrast is what builds the depth illusion.
- Gloss varnish: Finally, coat the whole gem in gloss. This is where the glass feeling is born.
How is a lens different from a gem?
So what changes when you are painting a lens instead of a stone? Robotic and vehicle lenses follow the exact same logic; the gradient is just usually sharper and the single glint is kept more pronounced. The goal is to make the lens look more polished, more technological.
And if the lens or stone throws light around it, you can take the technique one step further. In that case, combine gems and lenses with OSL (object source lighting): bounce a faint colour onto the surrounding armour. That small touch makes the part look like it is genuinely glowing. To go deeper, see our OSL: Object Source Lighting guide.
Which paints and brushes do you need?
Good news: you do not need an expensive set. On a tiny surface, what matters is not how many paints you own but how well you control your brush.
- Paint: A dark base, a main colour, a transition tone and pure white are enough. Citadel, Vallejo, Army Painter or Scale75 all work.
- Gloss varnish: Citadel 'Ardcoat or any glossy varnish. This step is not up for negotiation.
- Thinner and glaze medium: These help you smooth the gradient. We cover controlled thinning in Thinning Paint: Two Thin Coats.
- Brush: A small detail brush with a sharp point (00 or 0). For the white dot, the tip has to stay genuinely fine.
- Optional: A thin Inking coat for saturation, and Edge Highlighting to define the rim.
The most common mistakes
Mistakes on a gem are small but always on show. Avoid these five traps and your work will come out far cleaner:
- Putting the glint on the wrong side: If the white dot lands on the same side as the gradient, the depth illusion collapses. The glint must always sit on the opposite side, in the dark zone.
- Making the dot too big: A fat white dot reads as an "eye." Keep it small and sharp.
- Skipping the gloss: A matte surface never feels like glass. Without varnish the job is only half done.
- Not smoothing the gradient: Stepped transitions make the stone look crude and cheap, so erase them with glazes.
- Inconsistent light direction: If every gem on the model glints in a different spot, the eye gets uneasy.
Pro tips
A few small habits make the result look expert:
- Use the same light direction and the same reflection position on every gem on the model, because consistency is what sells the illusion.
- On very small stones, a shortcut is enough: dark base, single white dot, gloss. At that size the gradient would be invisible anyway.
- Remember that the formula is identical in every colour. Blue uses dark blue–light blue–white; green and purple follow the same logic.
- When building the gradient with glazes rather than an airbrush, take your time; Glazing and Layering are the backbone of this job.
Frequently Asked Questions
Where exactly should the white dot go?
On the opposite side from the gradient, in the dark zone. Because light comes from above, the glint sits high while the gradient brightens low, and that contrast is what creates depth. If you put the dot on the same side as the gradient, the stone ends up looking flat and lifeless.
Is the gloss varnish really necessary?
Yes, if you want a glass effect. However good the paintwork is, a matte surface scatters light and the stone stays dull. Gloss varnish, on the other hand, physically makes the surface reflective and completes the illusion even in photos. Citadel 'Ardcoat is the classic choice.
Do I need every step on tiny stones?
No. On stones smaller than two millimetres the gradient is invisible anyway. At that size, a dark base, one small white dot on the dark side and a gloss coat are usually enough. Save your time for larger, more eye-catching surfaces.
Does the same formula work on blue or green gems?
Yes, the formula is colour-independent. You just build a gradient from a dark base to the main colour and on to near-white. Blue uses dark blue–light blue–white; green and purple follow the same logic. Only the white dot and gloss steps stay fixed across every colour.
What is the difference between a gem and a lens?
The logic is the same; only the presentation differs. Lenses usually get a sharper gradient and a more pronounced single glint, because they aim for a polished, technological look. Gems, by contrast, can have softer transitions. And if a lens glows, remember to bounce colour onto its surroundings with OSL.
Should I place the reflection dot with an airbrush or a brush?
The single white dot always goes on by hand, with a small sharp-pointed detail brush. An airbrush is far too broad for a highlight this small and crisp. So keep your brush tip genuinely fine and your paint at the right consistency — you want a controlled drop, not a runny one.
I struggle to smooth the gradient. What should I do?
Erase the transitions with glazes (transparent, heavily thinned paint) applied over and over. Work in thin, patient coats rather than one thick layer. Using a wet palette also keeps your paint at the right consistency and makes melting the steps far easier.
The key takeaway
In the end, painting gems and lenses really comes down to three things: dark depth on one side, a gradient brightening on the other, and a single sharp white dot on the dark side — then gloss. Once that logic clicks, you can repeat it in any colour and at any size.
Ready to try it? Just start with the right materials. Browse our shop for paints, brushes & hobby supplies and put a shine on your next model's stones.