Optics, Light, & Luminosity
A Little Bit of Optics, A Lot of Visual Poetry
There’s a reason encaustic feels alive.
It doesn’t just sit on the surface, it glows from within. Like breath caught beneath the skin. Like moonlight trapped in wax. If you’ve ever run your fingers over an encaustic painting and felt the illusion of depth, that shimmer, that pulse, it’s not magic.
It’s physics.
Reflection. Refraction. Scattering.
The trinity of light that makes wax so seductive.
When light hits a surface, three things happen:
Reflection—light bounces off.
Refraction—light bends as it passes through.
Scattering—light diffuses as it moves through a semi-transparent medium.¹
With encaustic, all three occur simultaneously. The surface reflects like satin, the layers refract like glass, and the wax scatters light like mist trapped in amber.
This is what gives encaustic its signature “wet look.”
It’s uncanny resemblance to human skin.
Its a strange power to look lit from within.
Snell’s Law and the Refractive Index:
The Secret Science Behind the Glow
Light travels at different speeds through different materials. When it transitions between two mediums, say, from air into wax, it bends. This bending is known as refraction, and the angle of that bend is determined by each material’s refractive index (RI).²
Snell’s Law (simplified):
n₁ × sin(θ₁) = n₂ × sin(θ₂)
Where:
n = refractive index of each medium
θ = angle of the light ray in that medium
The refractive index of encaustic medium (beeswax + damar resin) averages around 1.44.³ This is high enough to trap light for a glowing effect, while still allowing internal light travel, key to encaustic’s luminous appearance.
Encaustic vs. Varnish: More Than Skin Deep
In oil painting, a varnish layer is often applied to restore saturation and unify surface gloss. That varnish acts like a topcoat; it enhances, but it sits above the painting.
Encaustic is fundamentally different.
The wax is the painting. It’s both pigment and binder, surface and substance. Each fused layer interacts optically, not just as a sealant, but as an internal reflector.⁴
Encaustic = varnish + depth + soul.
Subsurface Scattering: The Secret of Skin
This light-diffusing optical effect is called subsurface scattering. It’s the same phenomenon that gives human skin, marble, and wax their lifelike glow.⁵
Light enters the wax, bounces between layers, then exits, filtered, softened, and warm. The result is a glow that feels organic. Skin-like. Even otherworldly.
A Final Note on Poetry and Physics
Understanding optics doesn’t kill the magic.
It teaches you how to command it.
With every layer of wax, you're not just painting,
You’re sculpting light.
You're bending photons into poetry.
Footnotes
CIE (International Commission on Illumination), “Fundamentals of Light and Color,” Technical Report CIE 015:2018.
Hecht, Eugene. Optics, 4th ed. Addison-Wesley, 2001.
Velo, M. “Optical Properties of Beeswax and Damar Resin in Encaustic Media.” Journal of Art Materials and Chemistry, Vol. 12, No. 2, 2015.
R&F Handmade Paints, “The Encaustic Technique,” Technical Resource Library.
Jensen, Henrik Wann. Realistic Image Synthesis Using Photon Mapping. A K Peters, 2001. Subsurface scattering is widely cited in both computer graphics and conservation science.