Art Glass

During the early 20th-century art glass was generally made by teams of factory workers, taking glass from furnaces containing a thousand or more pounds. This form of art glass, of which, Tiffany and Steuben in the U.S., Galle in France and Hoya Crystal in Japan, Royal Leerdam Crystal in the Netherlands and Orrefors and Kosta Boda in Sweden are perhaps the best known, grew out of the factory system in which all glass objects were hand or mold blown by teams.

Most antique art glass was made in factories, particularly in the UK, the United States, and Bohemia, where items were made to a standard, or "pattern." This would seem contrary to the idea that art glass is distinctive and shows individual skill. However, the importance of decoration – in the Victorian era in particular – meant that much of the artistry lay with the decorator. Any assumption today that factory-made items were necessarily made by machine is incorrect. Up to about 1940, most of the processes involved in making decorative art glass were performed by hand.

source: wikipedia