If you’ve ever stared at a Christmas tree and thought, how can something so simple feel so magical?—a big part of the answer is light. Not just “pretty light,” but physics-and-perception light: photons bouncing, colors mixing, pupils adjusting, and your brain doing a little holiday trickery.

Today’s topic is one of my favorites for Art + Science: why Christmas lights glow the way they do, and how you can use that knowledge to make your drawings and paintings look lit from within.

1) Why Christmas lights look “warmer” than daylight

Most Christmas lights lean toward warm colors—soft yellows, oranges, and reds—because our brains associate warm tones with firelight and coziness. But there’s also a real science reason they feel gentle:

• Warm whites have more energy in the red/yellow wavelengths and less in the blue.

• Cool whites lean more blue and can feel “sharper” or “cleaner,” like midday sun.

Art trick: If you want cozy, push your highlights slightly toward yellow/orange and keep shadows slightly cool (blue-violet). That warm/cool contrast makes glow pop.

2) LEDs: tiny semiconductors doing a holiday performance

Most modern Christmas lights are LEDs. They aren’t “hot filaments” like old incandescent bulbs. Instead, they work because electrons move across a semiconductor junction and release energy as light.

What’s the artist takeaway?

• LED colors can be super saturated

• They often have harder edges and cleaner color separation

• They can produce a “neon-like” intensity that’s fun to paint

Art trick: Don’t blend LED colors too much at the source. Keep the bulb’s brightest part crisp, then let the glow soften outward.

3) The glow isn’t the bulb—it’s the air (and your eyes)

Here’s the secret: a glowing light looks like it has a halo because of:

• Bloom (light scattering in the camera lens… and in your eye)

• Atmospheric scatter (dust, humidity, tiny particles)

• Retinal/brain response (bright points “spread” a bit in perception)

Art trick: The glow is a gradient that fades into the background. The bulb is the sharp core. Think: core → halo → atmosphere.

A simple glow recipe (works in any medium):

1. Paint the background first (darker than you think).

2. Add the bulb shape in a bright midtone version of the color.

3. Add a smaller almost-white highlight inside it.

4. Add a soft halo around the bulb (same hue, lower opacity).

5. Add subtle reflected color on nearby surfaces.

4) Color mixing: why red + green lights can muddy fast

When colored lights overlap (especially in photos), your brain expects richness—but paint can turn into mud if you mix pigments directly.

Science note: Light mixes additively (RGB). Paint mixes subtractively (CMYK-ish). That’s why overlapping colored lights in real life can feel luminous, but mixing those pigments physically can dull.

Art trick: Instead of mixing red and green together into a brownish blend, layer them:

• Keep red light and green light as separate glows

• Where they overlap, lighten the overlap area slightly rather than mixing muddy pigment

• Use a neutral “bridge” (soft warm gray) to transition if needed

5) A quick “glowing ornaments” mini exercise

Try this 10-minute study:

Materials: any (digital, watercolor, acrylic, markers, pencil)

1. Make a dark background (deep navy, pine green, or charcoal).

2. Place 5–7 light dots across the page (vary size).

3. Pick 2 light colors only (example: warm white + red).

4. For each light:

   • Bright center

   • Soft halo (bigger than the center)

   • Tiny white specular highlight

5. Add one ornament ball beneath a light and paint a soft colored reflection from the nearest bulb.

If you do nothing else: dark background + bright core + soft halo will instantly read as “glow.”

6) A little wonder: your brain is part of the art

Your eye adapts to darkness, and bright points feel brighter because of contrast. That means you can create “wow” with less paint than you think.

Art trick: Make the scene darker and quieter overall, then place only a few true bright highlights. The glow will feel brighter because your composition supports it.

A simple holiday prompt (for your sketchbook or studio)

“The Quiet Physics of Christmas Eve”
Draw or paint a corner of a room lit only by tree lights. Include:

• one reflective ornament

• one shiny ribbon

• one soft texture (blanket, sweater, pet fur)

• 5–10 lights with varied glow sizes

Optional science twist: add a tiny “note” in the margin labeling your glow layers:
core / halo / reflected light / ambient shadow