Although not especially uncommon, a particular feature of today’s glass is a sumptuous example of its kind, and it’s not at all unreasonable to laud such finery when the occasion presents itself. It’s a mid-18th Century cordial glass, fairly simply engraved with flowers and leaf fronds, but exhibiting a pair of very splendid and gloriously bright mercury-twist corkscrew bubble-tapes enclosed within its stem.


Air-twists are one of the most alluring decorative touches added to antique glassware, but it is entirely likely that the premise behind them was discovered inadvertently. The production of crystal glass was – given the nature of the raw materials and the immediate proximity of the creative process to fire – an essentially grubby procedure, and no matter how clean the craftsmen might try to keep their workplace, the molten mass of glass with which they worked would inevitably become contaminated with minute specks of dust or dirt which would instantly vaporise in the searing heat; this would leave the tiniest of pockets in which air could become trapped. Similarly, the act of moulding and working the glass could also enfold air within the melt. It was usual for such a paraison (the technical term for a piece of work-in-progress molten glass) to require considerable manipulation as it was formed into something approximating its finished shape – marvering or rolling, stretching and twisting. It would have been observed that once the paraison included a bubble, it was almost impossible to get rid of the imperfection; the material – at working temperature – was too thick to allow the air to escape, and too thin for it to be simply squashed out of existence. It would also have been noticed that as the paraison was stretched, so the bubble distorted, and as it was twisted, so the bubble followed suit, becoming an integral part of the mass of glass rather than an independent ‘foreign body’, drifting around at its own volition.


It didn’t take long for the glassmakers to realise that these imperfections could be purposefully introduced with some semblance of control (by pricking the melt with needles or nails), and then manipulated to their advantage to create decorative features. Initially, these were mostly in the form of more conventional bubbles, known as tears (rhyming with ‘beers’), but as soon as it became apparent that they could be worked into more aesthetic forms, the trend for air-twist decorated stems quickly gathered pace.


Inevitably, increasingly complex uses of the technique were developed; combinations of canes each containing their own spirals gave rise to ‘multiple series’ twists and using both bubble-generated and opaque enamel features in one composite stem led to ‘mixed twist’ examples. It was also noted that the nature of the bubbles themselves gave rise to different effects. Very fine, round bubbles generated imperceptibly delicate gauze twists, less elongated rounds created miniature tubes known as cannulae throughout the otherwise solid stems, and if the bubbles were compressed to some extent, they took on a life of their own. Given an elliptical profile, a bubble would have two opposing planar surfaces, both of which had the ability to refract and reflect light, with the flattest variety known as tapes giving the most pronounced effect. As with any reflected light, there is the potential for increased brightness, even if only as a perceived effect, and that is what these tapes produced – the impression that, within the glass stems, there was a bright, reflective tape with a mirror-like finish. Now, early mirrors were made by coating glass with mercury and it was not, therefore, an enormous reach in understanding for these new, shiny, eye-catching features to become known as mercury twists, as if their appearance relied upon the same curious alchemy that permitted the beaus and belles of the day to regard themselves with vainglorious delight in their new-fangled mirrors.