Black Pottery of Verdú Curiosity · Verdú, Urgell, Lleida Image of Verdú, not of the place itself. Traditional ceramic technique practised in Verdú (Urgell, Lleida), documented in the town since the 13th century and devoted above all to black ceramic water jugs, called locally “sillons”. The darkening of the clay, originally reddish, occurs during firing, when the kiln becomes enriched with carbon and hydrogen in the absence of oxygen, causing a chemical reaction that blackens the piece; polished or burnished afterwards, it takes on more or less glossy black tones. Besides the change of colour, these chemical changes give the clay a consistency and hardness closer to stone, which increases its durability. It is a primitive technique, found in Asia, Europe, America and Africa with pieces dated as far back as before 1000 BC. Photo: Wikipedia / Wikimedia Commons (CC BY-SA) What to see and do in Verdú