From the XIth to th XIVth century, the techniques evolve/move but especially of new materials produced by specialized craftsmen are employed: the phenomenon is all the more significant since it goes hand in hand with other comparable innovations in other sectors, and in particular in the frame. Thus stone construction, there or it is available, or out of brick, near clay layers, appear and spread themselves with the emergence of the feudal company. In addition, the product obtained, the house, changed nature: it becomes a permanent, transmissible masonry during some generations and sheltering consequently a family. A new mentality, a new form of relation between the human ones and their house appear then.

The brick is present in Europe among Romans, but it does not re-enter in manners of the High Age means, that which concern to us appears towards 1170, along the coasts of the North Sea in mobilities of the religious commands Cisterciens and Prémontrés, large builders of monasteries and churches. In Flanders, the first traces of manufacture of bricks are due to the cistercians of the abbey of the Dunes of Coxyde towards 1220. These monks essaimèrent, and in XIIIème century those of Clairmarais have a tilery like perhaps those of Bergues and Bourbourg. It thus seems that these religious commands are the first to have manufactured bricks on an industrial scale, which is explained especially for reasons of a nature financial and practical, the chain implemented not being profitable immediately, although all the elements necessary were on the spot (clay, water, sand, wood). The production of bricks required a complex infrastructure making it possible to coordinate all the stages of the production: winning and preparation of the clay, moulding, drying and cooking of bricks out of grinding stones, transport - supported in maritime plain by a significant network of navigable water ways.

The cooking of bricks requires a temperature higher than 900°C during several hours. The oldest technique seems to be the grinding stone: made temporary structure of bricks they-even, piled up in lines alternated with fuel. With 4 to 10 m on side on 3 to 6 Mr. height, these structures of at least 40.000 bricks, were covered with clay to form a true room of cooking. This mode of cooking will perdura until the beginning of the century in, then the still many ones, brickyards of the area. At the time, the brick of " Bernard saint " is different from our since its basic module is of 29x14x9,5 cm. This one progressively will be reduced and approached the current module (approximately 20x10x7,5 cm), while taking to a dominating place initially in the religious architecture and soldier then civil (markets, belfries, town halls) and urban with the typical Flemish frontages with pinion in degrees (Arras, Furnes...). They replace by là-même constructions with wood sides, just like it thatch was replaced little by little for reasons of security and solidity by the tile.

The littoral origin of the plain makes that local clay is strongly sandy giving after cooking a brick or a yellow tile of hue to orange typical of the Flemish buildings of this microcomputer-area, and, although massively replaced by red bricks during the rebuilding which followed the Second World war, the yellow brick is and remains a symbol identitaire extremely.

Our experiments on the realization of bricks primarily related to the preparation of clays of different sources: steeping, malaxation, addition of sandy grease-remover according to the composition of clay, realization of moulds and mouldings. Our tests (not very conclusive) of cooking out of grinding stone having quickly convinced us that the difficult art of cooking could be made only on one such quantity of bricks that we defer for the moment such an experiment.