With the 2008 acquisitions of the Belgian manufacturer Demeyere (stainless steel cookware) and the French group Staub, which produces cast iron cookware, Zwilling moved to expand the cookware segment of its business. In 1976 Henckels introduced The Four Star line which is a fully forged knife with a molded handle made of polypropylene and a tang which extends into the handle. The majority of Zwilling knives have blades constructed from high carbon, stainless steel which is ice hardened for sharpness and stain resistance, along with a partnership allowing some products constructed using a micro carbide powder steel with clad layers and is manufactured in Japan. Henckels knives are manufactured in several ways. A large selection of the knife range are forged from a single piece of high carbon stainless steel, which is cold hardened to improve stain resistance. This hardening process consists of cryogenic tempering, and involves immersing the finished knife blades in liquid nitrogen. This process is required to get full hardness from most stainless knife steels, as it completes the conversion of austenite to martensite. The process of forging is intended to produce improved cutting-edge retention, weight, balance, and reduced opportunity for metal fatigue. Nearly all of Zwilling's knives are manufactured in Solingen, Germany. In 1909 Henckels set up its first subsidiary in the U.S., followed by Canada, the Netherlands, Denmark, Switzerland, Japan, Italy, France, Spain, China. In 2008, subsidiaries were set up in Great Britain and Brazil.