In the manufacture of ceramics, feldspar is a group of minerals and the second most important ingredient after clay. Feldspars are used as fluxing agents to form a glassy phase at low temperatures in glazes. They improve the strength, toughness, and durability of the ceramic body, and cement the crystalline phase of other ingredients. No other raw material is closer to being a complete stoneware glaze on its own than feldspar.
Gunnar Nylund was undoubtedly one of the masters of this technique, which played a crucial role in Rörstrand’s fame. His mastery also came from his collaboration with the chemist Nathalie Krebs, with whom he founded the Saxbo workshop.