Four quadrant dating
Farnsworth & Walthall (2011) found in their monumental study of Illinois bottles produced between 1840 to 1880, that bottles made by East Coast glass houses were smooth based beginning about 1856, whereas bottles produced in and around Pittsburgh, PA.("Midwestern" glass houses) did not produce smooth base bottles (i.e., used snap case tools) until about 1860.The point here is that close scrutiny is often necessary to conclude that a pontil rod was not used in the manufacture of what appears to otherwise be a very early bottle.The rest of this section is an overview of the main types of pontil scars: glass tipped pontil scar, blowpipe pontil scar, sand pontil scar, and bare iron pontil scar.Certainly there were differences between individual glass companies in both of these large glass making regions, but the noted trend was supported by their exhaustive research of hundreds of bottles and the companies that used them. Certain classes of "specialty" bottles were made using glassmaking techniques from earlier times.
Pontil scars on all types of "utilitarian bottles" (discussed below) became ever increasingly unusual as the 1860s progressed and largely disappeared by the late 1860s or early 1870s as various "snap" or snap case tools dominated the task of grasping the hot bottle for finishing (click on the previous link to view the discussion on the main Bottle Bases page)., which sunk off the eastern U. coast later in 1865, also showed that a large majority of the bottles were not pontil scared (Gerth pers. The first use of the snap tool in the United States may have been in the late 1840s (in Europe possibly as early as the 1830s) though its use was definitely evident by at least the early to mid 1850s.
To view a picture of an early American flask that appears to have been fire polished click sunburst flask.
This flask, classified as GVIII-2 by Mc Kearin & Wilson (1978), was produced in Keene, NH. Though likely fire polished, this bottle still has the pontil scar in evidence.3.
By our invention we obviate all the difficulty attending the old method for finishing the necks of bottles.
Pontil rods and the resultant pontil scars go back to antiquity, having been used for bottle making as early as Roman times (Mc Kearin 1941).