According to Wikipedia, blow molding is the process of using air to blow hot material into a hollow shape. This was first used with glass, with a molten glass blob being blown through the end of a blow pipe into shapes of bottles and other useful forms. This process was used by the Syrians,Egyptians and Europeans. In 1851, S.T. Armstrong filed a U.S. patent reference to blow molding a plastic material other than glass. In the mid 1930s, ICI (Imperial Chemical Industries) developed low-density polyethylene (LDPE), which was commercialized in 1939 and perfected in 1945 for squeeze bottles. In 1938, Ferngren and Kopitke produced a blow molding machine and sold it to Hartford Empire Company. This was the beginning of the commercial blow molding process. During the 1940s the variety and amount of products were still very limited and therefore blow molding did not take off until later. Once the variety and production rates went up the amount of products created followed soon thereafter. In 1950, Kautex Werke (Reinhold Hagen, Germany) developed and soon offered the first commercially available blow molding equipment. In 1953, high-density polyethylene (HDPE) was discovered. With the appearance of HDPE in the marketplace, a virtual explosion of blow molded products occurred in both Europe and North America.
In the 1950s, blow molded Christmas figurines for outdoor use began to be produced and the proliferation of these popular figurines has continued to the present day. The blow mold industry has been affected by the introduction of inflatable outdoor display units, but the older figurines remain popular with collectors.