First, the design department designs the shape of the object. A plaster model is then developed in the form workshop. This model is used to produce the shape, a hollow shape gypsum into which the liquid clay is then poured. The plaster draws water from the mixture that contacts the walls and forms a crust.
Once the crust reaches a thickness of about 8 mm, the mold is turned “upside down” in order to remove the excess liquid clay. The object then dries 4 to 5 hours, is then removed from the mold and left to dry for a further 24 hours. In the production department, the seams and other imperfections are removed.
Now, the piece is fired over night at 1050 ° C (1920 ° F). The ensuing white terra cotta is called biscuit. The motif that matches the decor designed by the artist is printed on the piece with black ink. These black lines prevent leakage and the mixing of the colors. To this day, this is the only known technique of enameling applied to ceramics.
Each area created by the black lines is now covered with a glaze by hand. A mixture of crystal powder and colored oxides is applied drop by drop. The glaze droplets dry on contact with the biscuit, therefore it is impossible to paint on the decor. The result is thus completed by the time-consuming method of pushing one drop onto the next. Each piece is completed by a single craftsman.
Once the piece is decorated, it is baked overnight at 750 ° C (1380 ° F). Most of the pieces have to be then be retouched and spend another night at the same temperature in the oven. Only then are the precious metals deposited and the piece has to be fired again at 600 ° C (1200 ° F). Finally, the vase is washed with a mixture of burnt sienna, earth and water, so that the crackle is visible in the glaze.
This very special ceramic technology is extremely difficult to handle, but it leads to a unique result: Longwy pieces are covered with a very thick layer of colored glaze much thicker than other ceramics. This gives the decor both volume and the deep color, which is otherwise not reached in ceramics.