6. THE PONTIL-MARK
I mention this last because it does not apply to all old glass; it does not apply to glass that was cast or moulded, but it applies to all old blown glass, and is a very important test and guide indeed.
UNDER-SIDE OF WINE GLASS FOOT, SHOWING THE PONTIL-MARK AND THE HEMMED OR “FOLDED FOOT” EDGE
The pontil-mark is either a depression in the glass, shallow, about the size of the third finger-end, or a lump about that size, standing up from the level of the glass around it. The pontil-mark indicates first that the piece of glass was originally blown, and second that before removing the blow-pipe the workman, as usual, attached the blown glass to a pontil. The pontil or punt is an iron rod, joined to the vessel by a little melted glass while the vessel is still hot. When the time comes for taking away the pontil, it is done by contact with cold water, which causes the glass to contract around the pontil-end and the pontil to become detached. Glass vessels which were blown, only, show the depression or the lump accordingly: blown-glass vessels which were afterwards “cut” show it in part only, or not at all, if the glass-cutter removed it: vessels neither blown nor cut, but cast in a mould, do not show it because they never had it. In the eighteenth century and the first quarter of the nineteenth, glass moulding seldom took place; so that the presence of the pontil-mark, whether it be a hollow or a lump, usually indicates age in the vessel which shows it.
In the oldest glass the pontil-hole is flaked with something which rather resembles mica. In the oldest wine glasses the pontil-lump stands out knobbily. In every case there are signs of the local fracture. As a rule, the older the glass the bigger and rougher the pontil-mark.