Footnotes

Provenance
Private British Collection

The manufacture of gold-ruby glass was perfected in around 1680 by Johann Kunckel (c.1637-1703), the German apothecary and alchemist, whilst working in Potsdam at the laboratory and glassworks of Frederick William, Elector of Brandenburg and Duke of Prussia. Whilst it was previously known that a ruby-red colour could be obtained by adding gold to a glass batch, it was an exceptionally difficult process to master and production had therefore previously been restricted to much smaller applications. Kunckel was the first to produce brilliant thick-walled glass vessels in this rich red colour imitating true ruby gemstones such as this. Their production peaked in the 1690s and continued well into the 18th century, with such vessels being highly prized owing to the immense difficulties faced in achieving the colour.

This remarkable goblet, a true masterpiece of Baroque art, is paralleled by only one other now in the Rijksmuseum in Amsterdam (inv. no.BK-2023-6), which was thought to be unique in form until the discovery of the present lot. The distinctive shell-shape of both goblets is reminiscent of rock crystal and elevates them into a league beyond other recorded gold ruby or Rubinglas works by Kunckel, which are of a more traditional goblet or beaker shape. The bowl of the Rijksmuseum's goblet is finely engraved with putti amongst fruiting vine, attributed to the master engraver Gottfried Spiller (1663-1728), who is known to have decorated several pieces of Rubinglas made by Kunckel in Potsdam.

The present lot differs from the Rijksmuseum goblet and indeed many of the earliest pieces of Rubinglas in its lack of engraved decoration, being instead entirely decorated in Hochschnitt. One of the earliest comparable pieces is a Hochschnitt goblet and cover formerly in the Hohenzollernmuseum in Berlin, tragically destroyed during the War, see Dedo von Kerssenbrock-Krosigk, Rubinglas des ausgehenden 17. und des 18. Jahrhunderts (2001), p.67 and no.5. This is illustrated by Robert Schmidt, Brandenburgische Gläser (1914), Table 16, no.5, there attributed to Gottfried Spiller. The stiff-leaf border around the rim of the cover of the Hohenzollernmuseum goblet is paralleled almost exactly by that around the foot of the present lot. Similarly, the stiff-leaf borders to the cover and base of the bowl are identical to those seen around the foot, stem and base of the bowl of the present lot, and the scrolling tendrils on the cover are also comparable to those seen here on the front of the bowl.

Decoration of this type is unusual for Brandenburg and instead reminiscent of the early Silesian Hochschnitt glass developed to imitate highly-valued rock crystal by Friedrich Winter in the Hirschberger Tal in around 1680. Von Kerssenbrock-Krosigk (2001) highlights the difficulties in dating these glasses owing to the absence of datable features such as armorials, but ascribes them to the late 17th century. The Rijksmuseum's example is dated to circa 1685-90, Kunckel's first decade as glassmaker to the royal court of the Elector of Brandenburg. There is little doubt that the present lot is of contemporary manufacture and it therefore represents a significant and early addition to the twenty or so extant glasses attributed to Kunckel's oeuvre.