Wet-Lime Plaster Arayash Burnishing & Mineral Pigment Frescoes in Shekhawati Havelis

At the scientific core of Arayash (or Mohrakashi) lies the ancient limestone cycle. The raw material begins as pure calcium carbonate limestone quarried from regional geological deposits such as Gotan in Rajasthan. Burned in kilns at temperatures exceeding 900 degrees Celsius, limestone sheds carbon dioxide to become caustic quicklime (calcium oxide, CaO). When water is added in large slaking cisterns, a violent exothermic reaction produces calcium hydroxide putty (Ca(OH)2), or slaked lime.

Unlike modern fast-setting cements that cure through hydraulic crystallization, slaked lime hardens solely through carbonation: it must absorb carbon dioxide directly from the atmosphere to revert to solid calcium carbonate (CaCO3). To formulate Arayash, this aged lime putty is combined with pulverized white marble dust (sang-e-marmar) sourced from the renowned quarries of Makrana—the same translucent white stone used to build the Taj Mahal. The marble dust provides both an ultra-pure structural aggregate and microscopic nucleation sites that guide the growth of calcite crystals into an interlocked, monolithic stone matrix.

What elevated Rajasthani lime plaster to world renown was the sophisticated empirical addition of organic botanicals, known locally as the master mason's 'secret brew'. Working in extreme desert temperatures that would flash-dry standard European lime mortars within minutes, Shekhawati builders developed an organic cocktail to modulate the plaster's rheology.

Chief among these additives was gur (fermented dark jaggery) and methi (fenugreek seed mucilage). When boiled in water, fenugreek seeds release dense galactomannan polysaccharides, while jaggery introduces complex carbohydrates. These natural polymers act as powerful water-retention agents and setting retarders, keeping the microscopic pore capillaries filled with moisture for hours. Additionally, sour curd (dahi) and egg whites were introduced into the final coat; their milk proteins (casein) and albumins formed insoluble calcium proteinate complexes, rendering the finished Arayash surface naturally hydrophobic, water-shedding, and resistant to desert rainstorms.

The signature hallmark of Arayash is its reflective, mirror-smooth sheen—a finish so lustrous that historical accounts describe haveli owners using unpainted white Arayash walls to reflect candlelight into dark chambers. This optical glassiness is never achieved by applying modern varnishes or clear coats; it is produced purely through the mechanical action of agate burnishing (ghunti).

As the pigment layer settles and the plaster achieves a firm, leather-hard consistency, the artisan takes up a smooth, water-worn river stone—typically red agate, carnelian, or jade. Applying firm, rhythmic, overlapping circular strokes, the mason burnishes the damp surface. This intense compressive pressure collapses the micro-voids between marble particles, expels microscopic air bubbles, and forces free calcium hydroxide water to the surface. As the stone slides across the plane, it aligns the microscopic flat platelet crystals of calcite into a uniform horizontal plane. When light strikes this aligned crystalline surface, it reflects with optical specular brilliance, giving the wall the tactile smoothness and cool luminescence of polished marble slab.

Understanding the difference between fresco-buono (true wet fresco) and fresco-secco (dry painting) is critical to the conservation of Shekhawati's architectural heritage. In fresco-secco, paints mixed with animal glue, gum arabic, or egg yolk are applied onto dry, cured plaster. Over centuries of intense desert thermal cycling, these organic binders oxidize, become brittle, and decompose, causing the paint layer to flake away in scales.

In true Arayash fresco-buono, no glue or organic binder is used with the mineral pigments. The pigments are mixed solely with pure lime water and painted directly into the wet, un-carbonated plaster. As the slaked lime converts into calcium carbonate crystals, it grows around and over each pigment particle, encapsulating it permanently within the rock crystal matrix. Because the pigment becomes an integral part of the stone wall itself, it cannot peel, flake, or blister. Conserving these murals requires maintaining this chemical breathability, strictly avoiding modern acrylic coatings that trap moisture and ensuring that historic Arayash can continue to respire naturally with the desert seasons.