The production and structure of air twist glass stemware – some of the most beautiful of Georgian drinking glasses

Air twist glasses always feature in our sales catalogue, and this particular type of glass really does exhibit the inventiveness and quality of English 18th century glassmaking at its finest.

The inherent beauty of glasses with this type of stem comes from the likelihood that the process by which they could be made was in all probability discovered by mistake, and then developed in to an adroitly-applied elaboration. It therefore avoids the contrivance of something that had been deliberately sought after by judicious experimentation, and has the kind of purity of form that earnest research fails to impart to its results.

Georgian glass was, of course, the product of an almost entirely manual process and inherent in any such procedure was the possibility of mistakes or imperfections creeping in at one of the numerous stages. It had taken decades of experimentation by Ravenscroft and his fellow innovators to perfect the manufacture of high quality, lead crystal glass with as few flaws or inadvertent inclusions as possible, but one foreign body that it was impossible to exclude entirely was, quite simply, air.

If molten glass was rolled (or marvered) inexpertly, or if a speck of something combustible were to drop on to it and vaporise, then an air bubble could result. It was quickly realised that such bubbles could be added purposefully, giving rise to wholly intentional features known as tears (to rhyme with beers, rather than bears) and – then – that these bubbles, once trapped, could be stretched and drawn along the length of a stem as it was rolled and lengthened. Perhaps when a rod of still-malleable glass was rolled unevenly, it was then noticed that the “bubbles” themselves would distort along with the rest of the material to such an extent that they could be deftly manipulated by the glassblower, and that if the rods were to be twisted – which was already part of the production process to add integral strength – then the bubbles would follow the direction of the distortion and twist and stretch in to spiralling, helical inclusions the full length of the rod.
It became immediately apparent, once the basic functionality had been grasped, that multiple bubbles could be introduced in to a single rod or stem and very soon after the first air-twist glasses were produced, increasingly complex designs appeared which resulted in Multi-Series Air Twist stems – the fables MSAT’s which are amongst the most sought after of this rightly revered form of Georgian glassware.

The addition of the bubbles themselves could be effected by different methods. The mass of molten glass (known as the parison or paraison) could have “pockets” in which air could be trapped added to it by either being pincered, folded or by being pricked by sharp points before it was worked in to a rod. The latter method allowed the bubbles to be positioned in exact, relative positions, which therefore meant that the resulting stem would exhibit multiple, concentric threads which looked remarkably well aligned. However, the actually manipulation and stretching of the mass might not be so precise, and hence we are left examples where the rising twist of the spiralling threads seems erratically proportioned. To my eye, though, this lack of absolute uniformity imparts a really striking and quite obviously hand-finished appearance to the glasses, and gives them an enduring charm that you’d never get with the precision of a machine-made piece.

Further refinements to the technique saw the introduction of a process involving the combination of two or more initially separate rods with their own threads already included. These would be reheated, pressed together in long moulds and then re-marvered and twisted around one another, increasing the complexity of the structure and producing examples which would have, for example, a central double helix surrounded by a fine spiralling gauze. It has been noted that something in the region of 150 different combinations of air-twist components have been recorded !

The structure of the actual bubbles themselves was also to prove important. Simple, round bubbles would be extruded into extended tubes, exactly as if something had burrowed through the glass rod leaving hollow cannulae or pipes. These were therefore referred to as vermicular or vermiform – meaning nothing more or less than “wormlike”. If a flatter, more elongated bubble was imparted to the paraison before being worked, the extended thread would be left more like a flat tape than a round tube, and the planar “surfaces” imprisoned in the clear crystal would refract light producing a very bright, almost reflective appearance, as if the thread had been coated with silver, or mercury, as was the case with early mirrored glass. Although the metal was not actually part of the process, these became known as mercury twists, a name that is still used to describe them in spite of its inherent inaccuracy.

The use of air-twist decoration became inordinately popular toward the middle of the 18th century, and it is often prescribed as being at least partly as a result of the drawing-up of the Glass Excise Acts of 1745/46 that imposed punitive taxes on manufacturers based on the amount of raw materials they processed. It is mooted that producing items with partly “hollow” stems would reduce the amount of material used, and thereby the taxes which would be levied, but to my mind the reduction in weight of a finished piece would be so negligible as to be virtually undetectable by the somewhat archaic measuring equipment of the day, so this assertion should be treated with a degree of scepticism. It may well have been little more than a somewhat spurious claim on the part of the glass making trade in order to rail against the taxes by claiming an overall reduction in material usage and relying on a degree of ignorance from the revenue officers when presented with such “hollow-stemmed” items for consideration. What is less contentious is the fact that the feet of glasses made at this time became less substantial, and it was here that the necessary economies were made. I prefer to think that rather than being the means to a parsimonious end, the use of air twists was simply an expertly executed decorative method which resulted in some startlingly creative pieces, as collectable now as they would have been treasured when new – fashionable simply because they looked quite stunning !

Click on the link below to see our both our current and archived listing of air-twist glasses, which includes some extraordinarily fine examples…

air wist glass