The following is an excerpt from “Origine des Potiers de Grès d’Alsace,” Bulletin du Cercle Généalogique d’Alsace No. 60, written by Marcel Schmitter.

Alsatian stoneware pottery is characterized by its color (gray and blue), by its hardness and by the use of salt varnish.

It is distinguished from other stoneware pottery in France for its color of its material and the predominant use of the color blue. It is part of the Rhinean (from the Rhine River) clay.

In Germany, the manufacture of pottery is present in the 14^th century. The most well-known of old centers were: Raeren, Frechen, Siegburg, and Hoehr. The latest, situated south-west of the Westerwald, was given the appellation “Kannenbäckerland” (the land of pitcher bakers). The region is reputed for the abundance and quality of the clay. By the end of the 16^th century, several reputed potters came from neighboring centers and set up there. It resulted in considerable development of this industry until the start of the 18^th century.  There followed a period of saturation. A number of potters left to try their fortune elsewhere. Because of this, new centers were set up in other regions where the conditions were favorable. Some of these potters set-up in Alsace at the beginning of the 18^th century.

The following are additional notes that V. Schmitter emailed me in Feb. 2008:

In the article "Alsatian pottery" there was a translation error. The french word "grès" has two different meanings :

In the geological domain "grès" is a type of sedimentary rock composed predominently of  sandlike quartz grains cemented by lime, silica and other materials. The english name of this rock is sandstone.

In the ceramical domain "grès" is a heavy, dense, nonporous type of pottery obtained by baking the clay objects at a higher temperature (1250°C) than conventionnal pottery (900°C). In this case the english word is stoneware. In the past, before the expansion of the canning industry, stoneware pottery was mostly used as containers for foodstuff.