Four quadrant dating
For example, in the bare iron pontil section below is pictured an early 1850s mineral water bottle with an iron pontil that visually appears to be just a worn circular area in the middle of the base.Very little iron was left behind though this example does have some pontil rod induced "ridging" that indicates its use.The common mode heretofore employed has been to use a straight bar or rod of iron with a head or ball upon one end, to which, when it is dipped into the melted glass, a quantity of glass adheres.While in a semi-fluid or plastic state, and while the bottle is also in a plastic state, immediately after being withdrawn from the mold, the glass upon the rod or punty is brought in contact with the base or bottom of the bottle and immediately it adheres thereto, and the glass soon chilled, the bottle is made fast to the punty, so that the operator may finish the neck of the bottle in any desired form.
This likely happened with any of the empontilling methods discussed below but in particular is thought most likely with the sand pontil, glass tipped pontil, and bare iron pontil since examples of all have been noted that were very obscure and difficult to see (empirical observations).(The image to the left is of a late 19th to early 20th century turn-mold barber bottle that has a distinct blowpipe pontil scar with some residual iron, i.e., like a "combination" pontil .) Many specialty bottles were imported from Europe, though that fact may be hard to ascertain. Some early 19th century bottles - particularly decorative bottles intended to be kept indefinitely - were often fire polished as the final step in the production process.However, many specialty bottles, most notably liquor decanters, had the pontil scars ground away leaving a shallow depression where the scar used to be (Munsey 1970). Pontil rods were (and may still be) used up until recent times at Mexican decorative glass factories and by small scale art glass producers in the U. Fire polishing was reported to have been developed by the English in 1834, though some American flasks from an earlier period appear to have been fire polished.It is the most succinct period description of the use of a pontil rod the author has run across.
As discussed on the Glassmaking & Glassmakers page, various non-fusing, bottle base grasping tools (snap or snap-case tools) were already in use by glassmakers in the U. by the early 1850s (if not a bit before) to some degree and were dominant by the time of this patent was granted in November 1865; a patent for the refinement of such tools not for the concept itself: In the manufacture of glass bottles great difficulty has been experienced in holding the bottles in a proper manner for finishing the necks.
Occasionally, it appears that when the pontil rod was removed from the base of a bottle little or no glass and/or iron residue was left behind to indicate that a pontil rod was used.