Please be aware that in order to gain the maximum information about any particular bottle (e.g., dating, typing) the user must usually must review a number of pages within this website.
Unfortunately, the complexities of precisely dating bottles is beyond the scope of any simple key.
In short, there was (and is) nothing to stop a glassmaker from using an obsolete method in the production of a bottle.3.
Some technological changes were expensive and not adopted by glass makers until it became an "adapt or perish" issue and many glass factories just perished.
This bottle dating "key" is a relatively simple "first cut" on the dating of a bottle.
While running a bottle through the key questions, the user is frequently directed to move to other website pages to explain diagnostic features and concepts as well as to add depth and/or precision to the initial dating estimate.
Pontiled base fragments could also be from later produced "specialty" bottles which are described below.5.
Some bottle shapes are indicative of a particular manufacturing era, though many bottle styles/shapes were used for so many years - like the cylinder whiskey "fifth" or square snuff bottle - that the shape itself is not indicative of age.The shift to the fully automated bottle machine from mouth-blown and some semi-automatic methods in the early 20th century is the classic example (Toulouse 1967, 1969a). The same bottle could have been recycled and reused many times for many years before finally being discarded - entire or broken (Busch 1987).This was almost universal with many beverage bottle types (e.g., soda, beer, milk) but was variably common with just about any type bottle - especially prior to 1920.The information on this website will, however, usually produce a reliable manufacturing date range for a majority of American utilitarian bottles manufactured from the early 1800s to the mid-20th century.Using physical, manufacturing related diagnostic features, most utilitarian bottles can usually only be accurately placed within a date range of 10-15 years (i.e., 1870-1880 or 1885) . Like many industries making the leap from manual craftsman production to industrialization and automation, technological advances in bottle manufacturing were not immediately accepted by glass manufacturers or their workers.Of course, soda & beer were reused up until quite recently.