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Part 9. Opaque and Mixed Twist Stems, 1745 - 1780
Part 9. Opaque and Mixed Twist Stems 1745 - 1780.
Facon de Venese serpent stem goblet, the convoluted twists with opaque red, white and blue threads. Late 17th century, Ht. 29.3 cm. (Fitzwilliam C139.1912)
It would seem evident that the typically English opaque twist was derived from the air twist. However, the idea of using twisted drawn coloured threads goes back to antiquity and, as seen in Part 2, was extensively exploited a hundred years earlier by the Venetian glassmakers. This included the making of elaborate stems for drinking glasses like those on the right.
Opaque twist stem Masonic firing glass with terraced foot and dated 1767. Ht. 10.4 cmThe technology, however, has some similarities to that for making stuck shank air twists. The twist is prepared by gathering up into hot clear glass an arrangement of white or coloured rods laid out in a mould. This results in a short thick cylinder with the desired pattern of rods stuck to the outside. More clear glass is gathered over the top and smoothed in, after which it is then slightly drawn out to a thickness of about 4cm. as in the making of seaside rock. The rod is cut into short lengths called, from their appearance, carrots. These may be stored for later use or kept hot in the furnace and short lengths cut off to make a stem as required. If only straight stems with no knops are required then the atterned block may be fully drawn to the required stem thickness and pre-cut into lengths ready for use as was done in the stuck shank process for straight stems. The drawing and simultaneous twisting of long lengths requires considerable expertise although it greatly economises on the time spent by the glassmaker in his chair.
The process of gathering coloured rods from a mould may be repeated two or three times so that the twist patterns are disposed in clear concentric rings within the stem, sometimes twisting in opposite directions. These are identified as single, double or (rarely) triple series twists, producing a greater variety of more clearly defined patterns than is found within the air twists. 
A variety of opaque twist stem formations. Image courtesy of Bonhams.So much so that Barrington Haynes (Glass through the Ages) remarked "A schedule of the twist varieties has grown rather too long for convenience". The introduction of colour combinations, made particularly in London and in Stourbridge, adds to the variety. Some twists may contain as many as four different colours. Colour twists are traditionally dated about ten years later than plain white twists but there is no evidence that this is so.
Mixed twist goblet with a single opaque spiral thread enclosing an air rope. c.1760. Ht. 17.5 cm. (picture courtesy Bonhams)
Colour twist with three knops. As many as five knops may occur in plain white twists, a rarity enhancing the value of the glass. c. 1770. Ht. 16.7 cm.(picture courtesy Bonhams)
The introduction of the opaque twist may partly be seen as a response to public demand for something new when the immediate restrictive effect of the Excise duty had worn off. But the glassmakers also exploited the fact that enamel, the substance of the opaque rod, although a form of glass, was duty free.
Opaque twist stems, like the air twists, are characteristically English in their form and variety. But from around 1763 some copies were made on the continent in lead glass and may be characterised by Dutch engraving although representing only a small proportion of what had, by now, become a flourishing market. Their total number contests those of the plain stem glasses although made over a shorter period. Reproductions made a comeback in both the 19th and earlier 20th centuries as well as a few by studio glassmakers in the last quarter of the 20th century. These are easy to identify in that the foot, now made with a footboard, is too flat and may not have a pontil.
One challenging variation on the theme of opaque stem was the inclusion in the stem of an air thread combined with an opaque thread. These so-called mixed twist glasses required an expert glassmaker and hence are relatively rare, particularly with a mould-blown bowl or in a cordial glass.
In 1777, the government Excise caught up with the anomaly of not taxing enamel. This sounded the death knell of the opaque twist. By this time cut glass had already come into prominence as the century moved into its last quarter.
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