Leonardo’s Hidden Fire: How Da Vinci Scorched Wood Centuries Before Japan

Florence, 1492—A Secret in Smoke

On a rain-slicked afternoon, Leonardo da Vinci slipped inside the workshop of Santa Maria Nuova’s hospital and asked the carpenters for their worst off-cuts. Witnesses thought the polymath was planning another flying machine. Instead, he built a small furnace, raked the boards across the coals, and watched the surface blister into midnight black. The charcoal crust that formed was no accident; it was armor.

The Forgotten Recipe

Five centuries later, conservation chemist Dr. Francesca Gallo found a brittle sheet tucked inside the Codex Atlanticus. The ink—Leonardo’s mirror-script—described a process of "ricoprir legnami col fuoco per non temer l’acqua né il tempo" (covering timber with fire so it fears neither water nor time). Carbon dating of surviving panels in the hospital attic matched the 1490s. The method? Rapid charring, oil quenching, and a final beeswax polish—three steps that create a weather-proof, insect-repellent shell.

"We always credited 18th-century Japanese yakisugi as the birth of fire-treated lumber," Gallo told our correspondent. "Turns out Leonardo beat them by almost 300 years."

From Atelier to Architecture

Leonardo’s goal was utilitarian: hospital beds needed wood that could be scrubbed with vinegar and boiling water without warping. Yet the aesthetic—ebon grain, silvery highlights where the scorching kissed lighter sap—soon graced choir stalls and ceiling beams across Tuscany. By 1500, a guild of maestri di bruciatura (burn masters) exported the technique to maritime Venice, where shipbuilders prized the charcoal skin for resisting salt rot.

Science at 800 °C

Modern tests at the University of Bologna recreated Leonardo’s recipe. Boards of alpine larch were exposed to an 800 °C flame for 55 seconds, plunged into cold linseed oil, then buffed with beeswax. Results:

• Moisture absorption dropped 62 % compared to untreated lumber.
• Termite mortality in controlled colonies reached 100 % within 48 hours.
• Surface hardness rivaled modern thermally-modified ash, a benchmark for premium cladding.

Global Echoes

Japan’s shou sugi ban and Finland’s torching share the principle of carbonization, but none pre-date Leonardo’s scrawled notes. The discovery rewrites not only art history—adding a pragmatic chapter to the da Vinci legend—but also offers green architects a Renaissance-tested, chemical-free method for durable façades.

The Phoenix Timber Revival

Italian start-up FuocoVivo now sells Leonardo-branded charred boards to eco-developers from Brooklyn to Brisbane. Each plank is laser-etched with a tiny Vitruvian Man, a nod to the master who once turned scrap wood into timeless design.