In Marsal, near Nancy (Moselle), are the remains of Iron Age sites (7^th to 1^st century BCE) for the production of salt. They made use of natural salt sources and are known as the “Briquetage de la Seille” (Seille brickwork). Since 2014, field work has been carried out by participants on an international professional training scheme, led by a team of professional researchers and doctoral students. The excavation shown here, at Pransieu, is focused on artisanal production sites dating from the 6^th century BCE. The aim of this study is to understand the organisation of Celtic salt workers and identify the techniques used for salt production in the Iron Age.