The Physics and Psychology of Stained Glass in Islamic Architecture: Qamariyyat and Shamsiyyat

In Islamic religious and palatial spaces, openings in the upper perimeter of walls or dome drums served as more than mere perforations for illumination. Master craftspeople developed stucco openwork grills embedded with colored glass, referred to historically as Qamariyyat (lunar, circular openings evoking soft light) and Shamsiyyat (solar, radiating lancet or arched apertures).

These apertures performed a twin function: solving a strict optical and thermal physics problem in sun-drenched climates while choreographing psychological and sensory transitions inside the space.

1. Thermal Radiation Filtering: Selective Wavelength Absorption

Direct daylight in desert and Mediterranean climates carries intense radiant heat alongside blinding illumination. Ordinary unshaded glass panes act as heat traps, drastically raising indoor ambient temperatures.

The Infrared Barrier: By utilizing thick, hand-blown stained glass, artisans introduced metallic oxide colorants (such as cobalt for blue, copper for turquoise and green, and manganese for purple/violet). These metal oxides absorb portions of the near-infrared and ultraviolet spectrum, blunting solar radiant heat transfer.

Reduction of Visible Light Transmittance (VLT): Reducing raw daylight transmittance to an engineered fraction softens the transition from harsh outdoor desert daylight (often exceeding 80,000 lux) down to a serene 200–500 lux interior level.

2. Deep Stucco Matrices: Built-In Solar Baffles

The true structural innovation of a Qamariyya is its thick framing material:

High-Depth Gypsum Tracery: Unlike slender European leaded cames (came glasswork), Islamic stucco traceries were cast in deep plaster molds, frequently measuring 5 to 10 cm in thickness.

Self-Shading Lattice: These deep, beveled plaster profiles act as micro-louvers. Direct low-angle and high-noon sunlight strikes the beveled edges of the plaster rather than penetrating directly through the glass, diffusing scattered rays into the room.

Thermal Buffering: Plaster is a natural insulating material with low thermal conductivity, preventing heat from conducting across window frames into interior surfaces.

3. The Psychology of Sacred Chromatics

The spatial distribution of colored glass followed a deliberate experiential logic:

Saturated Blues and Deep Greens (Contemplation and Coolness): Predominating in higher clerestories and prayer niches, cool wavelengths reduce ocular fatigue and physiologically induce a sensation of coolness in hot climates.

Amber, Ruby, and Gold Accents (Warmth and Divinity): Used sparingly as focal points, warm hues mimic the warm glow of sunrise or sunset, catching airborne dust motes in gentle volumetric shafts of light without causing distracting glare.

The Dynamic Prayer Carpet of Light: As the sun traverses the sky, the colored beams travel slowly across plain stone walls and floor carpets. This kinetic light movement marks the passage of time toward daily prayers, turning interior surfaces into living sun-dials.