Centuries-old Roman "wow glass" reveals stunning photonic crystal patina

A shard of ancient Roman glass, known as the "wow glass," has been found to possess a rare golden-hued patina with unique optical properties. The patina is the result of the corrosion process slowly restructuring the glass to form photonic crystals, which create iridescent colors. Photonic crystals are tunable materials that can block certain wavelengths of light while allowing others to pass through. Scientists are studying natural structural coloration to develop commercial applications, such as plant-based films that cool when exposed to sunlight and chameleon-like films that change color when stretched. The shard was discovered near the ancient city of Aquileia, Italy, which was once a thriving center for trade and glass processing.