Scientists find the secret of Spain's dazzling white pots

Scientists have discovered the secret formula that enabled Spanish court ceramicists to produce porcelain of dazzling whiteness envied throughout Europe more than 200 years ago.

Scientists have discovered the secret formula that enabled Spanish court ceramicists to produce porcelain of dazzling whiteness envied throughout Europe more than 200 years ago.

Fine porcelain of the Buen Retiro was produced from 1760 in jealously guarded secrecy in a factory in Madrid's Retiro park that had only one entrance, guarded by a soldier. The factory was seized and turned into a fortified arsenal by Napoleon's occupying forces in 1808, then bombarded, sacked and burnt to the ground by the Duke of Wellington's troops in 1812 in one of the fiercest battles of the Peninsular War.

Buen Retiro porcelain was a powerful competitor of Sevres, Meissen and fine English porcelain, and Spaniards always suspected that British and French troops destroyed the factory, its equipment and its records, to kill Spanish competition in this precious commodity.

The ceramic scientist Salvador de Aza said: "A cup and saucer cost the equivalent of £800 each in today's terms. Royal houses throughout Europe developed their own techniques to try to discover the secret."

Spanish production ceased with the destruction of the factory, and countless efforts since then have failed to reproduce the unique formula.

The secret was discovered by accident when an impromptu race-track set up in the Retiro caused subsidence and revealed ancient factory vaults, including remains of pots that could be analysed.

Scientists found the porcelain contained a number of minerals, including alpha-quartz and alpha-cristobalite, to which was added the locally available sepiolite, which provided the characteristic translucent whiteness.