Turn-molds: The turn-mold is more of a process than a mold and could be produced in about any full height round mold. All turn-mold bottles (also called a “paste mold”) are round in cross section since no other shape could be turned or twisted in the mold to produce the seamless body distinctive of these bottles. The inside surface of a turn-mold was coated with a “paste” of organic fiber (often sawdust) which was also wetted between each blowing. Upon contact with the very hot glass the water turned to steam. The steam formed a cushion that the bottle “rode” on while the parison was expanded and rotated by the glassblower. The combination of the steam cushion and the rotation contributed to a distinctive glossy or polished glass surface to a turn-mold produced bottle that other types of bottles do not have, with the exception of fire polished free-blown bottles (Toulouse 1969b; Munsey 1970). However, turn-mold bottles will be very symmetrical throughout; free-blown bottles will not be symmetrical (Jones & Sullivan 1989).
In addition, the granular texture of the paste on the surface of the mold and/or imperfections on the mold surface, in conjunction with the bottle rotation, very often caused the formation of concentric horizontal rings on the body of the bottle. It is known that some turn-molds were made of apple or cherry wood at the Whitney Glass Works (Glassboro, NJ) as late as the early 20th century (Lohmann 1972). Wooden molds would also be more likely to have uneven inside surfaces due to the effects of the extreme heat of the molten glass. Because of the rotation of the bottle in the mold and the wetted paste coating, whittle marks (discussed earlier) are rarely if ever seen on turn-mold bottles (Toulouse 1969b; Munsey 1970).
Because of the rotation of the bottle in the mold (not the opposite as the name “turn-mold” would suggest) embossing on the body of the bottle was impossible; labeling or the occasional blob seal was the only way to notify the product purchaser of what product the bottle contained (Toulouse 1969a) Virtually all turn-mold bottles also have no embossing on the base, though some limited embossing has reportedly been observed. This would have entailed a secondary molding base plate that replaced the original mold base plate after the bottle was rotated in the mold but before it cooled and solidified (Toulouse 1971; Lockhart pers. comm. 2004). In any event, base embossed turn-mold bottles are very uncommon and none have been observed by the author of this website.
It is possible that many or most of the turn-mold bottles sold by American glass makers were imported and not actually produced in the U.S. May Jones, in the first volume of her nine volume bottle history booklets called collectively the The Bottle Trail, quotes a Owens-Illinois Company provided history that notes that their predecessor (Illinois Glass Company) imported the turn-mold bottles they sold and that “…in the United States, turn mold bottles were not generally produced” (Illinois Glass Company 1903, 1908, 1911; Jones 1961). As noted earlier, it is known that the Whitney Glass Works (Glassboro, NJ) – a large producer of bottles – did manufacture turn-mold bottles with wooden molds as late as the early 20th century (Lohmann 1972). In addition, Toulouse (1969b) notes that patents were granted in the U.S. in the 1870s and 1880s for “seamless bottles.” So it appears certain that some turn-mold bottles were produced in the U.S. Although it is likely that many or even most turn-mold bottles were not made in the U.S., they are ubiquitous on U.S. historic sites that date from the 1880s through about World War I, though turn-mold bottles have been documented possibly by as early as the 1850s, but almost certainly by the mid-1860s (Switzer 1974; Beaudet 1981; Gerth 2006). For more information click turn-molds.
via Glassblower.Info – Cast Iron Molds and Paste Molds.
