This attachment process was called “empontilling.” The rod had to be long enough so that the heat transference from the extremely hot (2000° F.) bottle did not reach the hands of the pontil rod holder.
A pontil rod held the bottle during the steps in the bottle blowing process where the blowpipe is removed (“cracked-off”) from the bottle and that break-off point is “finished”, i.e.
The base of a bottle which was held with a pontil rod will almost always retain some evidence of the pontil rod attachment.
(For more information on the production processes of making bottles, please see my “Historic Glass Bottle Identification & Information Website” (HBW for short) at org/bottle/.
This type of pontil can be very subtle and hard to identify at times (it is also hard to photograph).
It often must be confirmed by running ones finger over the base and feeling for the presence of a finger grabbing “sandpaper effect.” It feels and visually appears to be a generally round, sparse scattering of very fine sand, glass, or quartz grains imbedded onto and into the surface glass of the base.
In actuality, the residual red, reddish black, gray, or black deposits are iron, typically oxidized iron – ferric (red) and ferrous (gray, black) oxides (Toulouse 1968; Mc Kearin & Wilson 1978).
When a blowpipe was used as a pontil, it left behind a distinctive ring shaped scar that is usually sharp edged, hollow in the middle, and round to slightly oval with an overall diameter that is roughly the size of the bottles upper neck.
In particular see the “Glassmaking & Glassmakers” page at org/bottle/) Four types of pontil scars There were four main types of empontilling methods – all of which leave more or less distinctively different base markings. Glass-tipped pontil scar (image #1) – This type pontil scar was formed by the use of a solid iron bar as the pontil rod.
One slightly widened end of the bar was tipped with molten glass then applied and fused to the base of the bottle.
This is circumstantial proof that one blowpipe was usually used for both blowing and empontilling.
Image #2 shows a very large and distinct blowpipe pontil on the base of a “Jenny Lind calabash” bottle that dates from about 1850. Sand pontil scar (image #3) – The sand pontil scar was also a common method of empontilling a bottle to hold it for finishing, though less common on American made bottles than the other three primary methods described here.