Delftware: blue, white and forgeries

Delft is not porcelain but faience: a porous clay covered with an opaque tin glaze on which the decoration is painted before firing. Hence its fragility and its charm.

The first reflex is to look for a chip on the rim. An old piece then shows a soft, yellow-beige body. If the break is white and hard, you are holding porcelain or a twentieth-century industrial copy.

Painted underglaze decoration shows slight bleeding and variations in the intensity of the blue: the brush loads then runs out. Regular printed decoration with a dot screen belongs to the late nineteenth century.

Marks — workshop initials, numbers — have been copied abundantly. They confirm a piece; they never guarantee it alone. Weight, dull sound and wear to the foot remain the best clues.