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All About Glass

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Gold Ruby Glass

All About Glass

Covered Goblet Brandenburg (Germany), Potsdam, about 1725–1735. Formerly in the collection of Jerome Strauss (S 1924). OH. 26.9 cm, D. (rim) 9.2 cm. The Corning Museum of Glass (79.3.318, bequest of Jerome Strauss).Gold ruby is arguably one of the most beautiful colors of glass. Beyond its aesthetic qualities, there is an alchemical connotation: Since ancient Greek times, descriptions of the sorcerers’ stone agree that it was believed to be a red substance and the key to the transmutation of metals, principally the making of gold (Ganzenmüller 1937; idem 1956, pp. 85–128; Kerssenbrock-Krosigk 2001, p. 13). Whoever discovered how to color glass red must have thought himself to be on the right track to attaining the ultimate goal of alchemy. The 10th-century Persian physician and philosopher Rhazes (about 865–between 923 and 935) apparently believed that he had already fulfilled that objective. In his formula, the earliest known written account of a gold ruby glass, he stated that this glass attracted gold and silver like a magnet, and that it could convert 1,000 times its weight into gold.1

About 800 years later, enthusiasm for gold ruby was at its peak. As far as can be determined from the legacy of princely treasures in today’s public collections, almost every central European sovereign seems to have owned one or more gold ruby glass vessels. This high point in the popularity of gold ruby glasses was confined to a relatively brief period: between about 1685 and 1705. It was preceded by a long history of developments that culminated in the production of large vessels that glow in a deep yet translucent ruby color. At its height, gold ruby glass was apparently considered to be not just another decorative folly but a genuinely new and precious material. It was ranked about as high as hard-paste porcelain, which came into production in Europe only a few decades later. During the 18th century, interest in gold ruby persisted in some regions and occasionally arose in others, but it never regained the widespread appreciation that it had engendered earlier.

The history of gold ruby has many beginnings. Red glass of some sort was produced almost from the time that glassmaking began. Knowledge was gained and then lost, and while there were rediscoveries on several occasions, this glass does not seem to have been produced again until it was revived in Brandenburg in the late 1670s and 1680s. It is here, with the arrival of the alchemist, pharmacist, and glassmaker Johann Kunckel (1637?–1703; Fig. 1) in early 1678, that the real story of gold ruby glass begins.

Johann Kunckel

Fig. 1. Portrait of Johann Kunckel, frontispiece of Kunckel 1689. Rakow Library Bib No. 81288.Kunckel’s first appearance at the Brandenburg court of Frederick William (r. 1640–1688), who was called “the Great Elector,” could not have been more successful. His writings indicate that the prince was highly interested in alchemy and wished to hear about his experiments. Frederick soon gave him an opportunity to demonstrate his talent. Kunckel was asked to comment on experiments made by an alchemist who was pretending to have made gold from silver. Kunckel quickly exposed the ruse, saving the prince from spending considerable amounts of money on the charlatanism of a so-called goldmaker.2

Kunckel’s entrance into the life of the court certainly impressed the prince, and a few months later, in the summer of 1678, Kunckel became Frederick’s valet de chambre and moved to Berlin. He was an eminently suitable choice for this position. The son of a “glass artist,” Kunckel had been born in the 1630s in or near Plön, a village southeast of Kiel. In the 1650s, he had become a pharmacist, engaged in alchemical studies, at the castle of Duke Franz-Carl von Saxe-Lauenburg in Neuhaus, south of Hamburg.3 In 1667, the elector Johann Georg II of Saxony (r. 1656–1680) commissioned him to undertake a formidable task. He was to go through the elector’s library of alchemical writings and uncover their secrets, chiefly regarding the making of gold.4 This assignment permitted Kunckel to study practically all of the available alchemical knowledge, gleaning some valuable insights from authors who had a serious interest in chemistry and developing an unmatched expertise in discerning the scams of all the others. In addition, he conducted his own experiments to evaluate the findings contained in his sources. It was probably at this time that he began to apply this empirical, scientific approach to glassmaking.

Ars Vitraria

Antonio Neri ’s L’Arte vetraria, published in Florence in 1612, is well known to English-speaking readers because of the annotated translation completed in 1662 by the librarian and natural historian Christopher Merret. The German version of this influential book, which was prepared by Johann Kunckel as Ars Vitraria and first printed in Wittenberg in 1679, has received less attention outside central Europe. However, Kunckel not only translated the work but also added significantly to its value (Kunckel 1679).5 Unfortunately, although Kunckel translated Merret’s comments into German, an English translation of Kunckel’s edition is still awaited. Neri had collected glass recipes, especially for colored glass and enamel colors, and made them public. Theretofore, compilations of glass compositions in manuscript form had been carefully guarded secrets, and Neri must have had a difficult time in assembling the information he published. Merret contributed a learned commentary, adding information on furnace construction as well as English raw materials and glass types.

For his part, Kunckel commented on the outcome of every one of Neri’s recipes, having tested them all himself.6 Frequently, he wholeheartedly endorses a procedure, as in his assessment of a blue color in book 1, chapter 23: “Within this chapter one has to follow the author [Neri] to the letter, and [this recipe] gives a very charming color of this kind.”7 Sometimes, however, he completely rejects a formula, as in his review of a shade of lapis lazuli in book 4, chapter 72: “The author shows, I am absolutely certain, that he did not try it himself, or else he would have regarded it differently and abstained from including it [in the book] because it does not work at all....”8

Kunckel frequently offers advice on how to adapt a process to northern European practices and raw materials. In his comments on a lattimo (white) color in book 3, chapter 55, he says: “The author teaches that the composition should stay in the furnace for 18 days and nights, which, however, is entirely unnecessary, especially in our German glass furnaces, where it should not stay longer than three days and nights. The content of manganese that the author is using is also too large....”9 In a few instances, he outlines wholly different solutions to the recommendations of his Italian predecessor, as in book 5, chapter 91.10

Gold Ruby

Sixteen of the 133 chapters of Antonio Neri’s L’Arte vetraria are devoted to red glass (cf. Kerssenbrock-Krosigk 2001, pp. 30–31). Nine of these offer formulas that produce more of a violet or brown color, and these are based on the use of manganese. Six formulas employ copper, which had a long tradition as a red glass colorant in cathedral windows and in translucent red enamels (rosichiero, or rouge clair) used by goldsmiths in the Middle Ages and the Renaissance. At the end of Neri’s treatise (book 7, chapter 129; Kunckel 1679, p. 169 and comment on p. 195), one recipe mentions the use of gold. It shows that the potential of using gold as a red colorant was fully understood in early 17th-century Italy. This knowledge may, in fact, date back to the 15th century or even earlier.11 However, it did not result in an abundant production of Italian gold ruby. The only known gold ruby vessels of Italian origin are a series of ribbed bowls, ewers, and bottles that King Frederick IV of Denmark brought back from a trip to Venice in 1708–1709 (Housed at Rosenborg Castle, Copenhagen (22-266, 22-259); Kerssenbrock- Krosigk 2001, pp. 56–58).

Neri’s recipe apparently works (it was tested under ideal conditions in 1930), but the author himself was rather doubtful and closed his discussion with the remark that “però si esperimenti per trouarlo” (but one should experiment to find it) (Zschimmer 1930, p. 642).12 Kunckel’s attempts to reproduce the recipe did not succeed, and he was also misled by an incorrect translation from the Latin, which turned the disclaimer into its opposite: “ut experimento compertum est” (rendered “as by experience is found” in Merret’s translation of 1662). In any case, the instructions would, at best, serve to produce an enamel color, and they are certainly insufficient for full-scale glassblowing.

In only a single instance, in the context of one of Neri’s instructions for a copper ruby glass, did Kunckel remark that he knew a better procedure:

Here I wished to indicate a better way, and to briefly teach [the making] of the red or ruby glass, if it were not regarded as such a peculiar rarity by my gracious elector and master. Whoever does not believe that I can do it may come and see it. It’s true: for now it is too rare to communicate.13

Kunckel may have deliberately chosen the comment on this recipe to communicate his own endeavors, rather than the only gold ruby formula in the book, in order to put potential competitors on the wrong track. A little earlier (September 1678), in a letter to the Nuremberg physician and scientist Johann Georg Volkamer, he enthusiastically reported that he had found the method of making gold ruby glass (Fetzer 1978, pp. 71–73; cf. Kerssenbrock-Krosigk 2001, p. 42). He did not claim it to be his own invention, but he mentioned instead experiments that had been performed in Hamburg by the physicist Andreas Cassius (1605–1673), as we learn from Kunckel’s posthumously published Laboratorium Chymicum, in which he offered a detailed report about his gold ruby glass (Kunckel 1716, pp. 652–655). Cassius was born in Schleswig, which is not far from Kunckel’s own birthplace, and he graduated from Leyden University. He created a purple-colored gold solution (purple of Cassius) by mixing gold chloride and stannous chloride in aqua regia (HCl / HNO3). His son, who was also named Andreas (1645–about 1700), published the procedure in 1685 (Cassius 1685, chap. 10; translated in Hunt 1976, pp. 138–139, and idem 1981, p. 64).

Purple of Cassius, as described by Kunckel (Kunckel 1716, pp. 382–383), was not invented by Cassius. Johann Rudolf Glauber had already described the process in principle in 1659 (see pages 64–65 in Glass of the Alchemists). This was the ideal raw material for gold ruby glass because it produces gold particles in the finest solution. When the finished product is reheated, the metallic gold forms nanoscale particles, which must be the right size and shape to convey a purple-ruby color through the absorption of light. If the gold colloids, as these particles are called, are too small, the glass remains colorless. If they are a bit too big and too much light is absorbed, the glass looks liverish (German, lebrig), or opaque brownish.

Alchemists and glassmakers of the Baroque period, of course, had not the slightest understanding of colloidal chemistry, and so they had to rely entirely on their own experience. It was one thing to make small samples of gold ruby in a laboratory, but quite another to blow an evenly colored vessel from this glass. How Kunckel and his gaffer managed to produce the large, impeccably colored goblets of varied thicknesses that we admire today remains an enigma. Developing the experimental creation of gold ruby into the production of vessel glass was Kunckel’s unique contribution. Based on the available sources, he had not yet attained success in 1679, when he published his Ars Vitraria, but he did so by 1684 at the latest (Kerssenbrock-Krosigk 2001, pp. 41–42).

This effort was not inexpensive. We know, from the files of later legal proceedings, that during 10 years of work, Kunckel earned 5,000 Reichstaler and received another 21,325 Reichstaler from his patron, Frederick William (ibid., pp. 39–40). Nevertheless, the elector remained enthusiastic. In 1685, he donated to Kunckel the Pfaueninsel (Peacock Island) in the Havel River between Berlin and Potsdam, one of the most romantic sites in northern Germany.14 The island provided the ideal location for a secluded research laboratory, and Kunckel’s production of gold ruby glass was apparently relocated there in an attempt to keep it away from the eyes of imitators. Additional marks of favor from Frederick William were to follow, but the enthusiasm did not last long. The elector died in 1688, and Kunckel became the target of those who envied his progress. His island laboratory was set afire, and he was accused of misappropriation. Kunckel nevertheless remained, for the most part, in Brandenburg, and he seems to have continued to make glass. But he had also developed a new scientific passion for mining. This led him, in 1693, to Sweden, where he attempted to improve the method of extracting copper from ore (Selchow 1984). Although this effort failed, the noble title “von Löwenstern” was nevertheless bestowed on Kunckel.

Brandenburg

Johann Kunckel described the making of his first gold ruby masterpiece as follows:

Then, the elector of Cologne of blessed memory demanded if I could make him a red chalice: a large inch15 thick, the stem a very fat knop, therein had to be screwed one end of the chalice, and the other end [of the stem] into the thick foot; and a cover with a finial of similar shape [as the stem]. I agreed, to which I was strongly encouraged by my late elector [of Brandenburg]: I should not cease, to obtain the honor that the first red glass be made here, no matter how much it may cost.

Although my first attempt failed because of the thickness, also considering that it should be even in color, I finally succeeded. The glass, which was very beautiful, weighed about 24 pounds. The elector of Cologne ordered the payment of 800 Reichstaler in cash, not counting what my master of blessed memory graciously donated on top.16

This event is undated, but it must have taken place about 1684, before the donation of the Pfaueninsel. Kunckel wrote his Laboratorium Chymicum about 10 years later, and we may wonder whether his account is altogether trustworthy. The weight, in particular, seems much too great for a Baroque glass vessel. On the other hand, this vessel marks an exceptional moment: the beginning of the production of glass of outstanding quality in Brandenburg. Not only was gold ruby glass a unique accomplishment, but it was also based on the creation of a truly refined crystal, which may well have surpassed in quality the glass that Kunckel’s continental European competitors were fashioning.

The goblet made for the elector of Cologne was sold for a price equivalent to one and a half years of Kunckel’s salary, and it may well have remained a unique piece. Unfortunately, this vessel has been lost, and we have no image of it. We know of it only from a 1786 account of Friedrich Nicolai that mentions “a beautiful chalice of red glass made in the former factory in Potsdam on order of the elector of Cologne.”17 At that time, it was in the possession of a Mr. Daum, who owned a residence on the Breite Strasse in Berlin as well as an estate near Charlottenburg (today part of Berlin). No other goblet of ruby glass is known to consist of three parts that are screwed into one another. This technique is a known, albeit rare feature among Bohemian and German colorless glass goblets, and it may have been required to produce a gold ruby goblet of unusual size.18

One additional aspect of Kunckel’s account is remarkable: He does not mention a gaffer but claims to have made the goblet by himself. It is an important but often overlooked point that the making of glass is rather different from the working of a glass vessel. Choosing the proper raw materials, mixing the batch, and controlling the melt require skills entirely distinct from those involved in the blowing and shaping of the final product. Even the relatively primitive forest glasshouses respected this division of labor, if only for the simple fact that if a gaffer had also been required to prepare the batch, he would have been deprived of the few hours that remained for him to sleep. Keeping molten glass hot was an expensive task, and the gaffers could rest only during periods in which the crucibles were being refilled.19 We know that Kunckel had the chemical knowledge necessary to produce the batch. It is very unlikely, however, that he was equally skilled in working with the blowpipe, which requires continuous practice. However, Kunckel states that he was “the son of a glass artist and educated among them, also trained from youth in this and various other arts of fire,”20 and as an alchemist, he may have manufactured his glass utensils himself. It is tempting to imagine that Kunckel took an active part in the shaping of some of his gold ruby vessels, especially because the process of making ruby glass did not stop with providing the molten glass, but was completed only after the finished object was reheated. This may have been a crucial problem in creating gold ruby glass: it required someone who was capable of supervising the entire process, from the purification of the raw materials to the annealing of the finished product.

Fig. 2. Goblet. Brandenburg (Germany), Potsdam, probably engraved by Gottfried Spiller, about 1690–1700. Formerly in the collection of Jerome Strauss (S 991). H. 24.1 cm, D. (rim) 11.7 cm. The Corning Museum of Glass (79.3.258, gift of The Ruth Bryan Strauss Memorial Foundation).

Gold ruby glass vessels of the Baroque period that were made in Brandenburg can be divided into two phases of production. The first phase began with Kunckel about 1684, and it came to an end during the reign of the elector Frederick III (r. 1688–1713; he crowned himself as King Frederick I in Prussia in 1701). We do not know if, or for how long, Kunckel continued to work in this field following the death of his patron, the elector Frederick William, in 1688. The second phase commenced about 1719, during the reign of King Frederick William I (1713–1740), and it continued, on a lesser scale, into the 1740s. The glass from these two phases can be distinguished not only on stylistic grounds but also by color: the early production displays a bright raspberry red, while the later glass tends to be darker.21 We know of as many as 22 vessels, goblets and beakers, that can be attributed to Brandenburg before 1700. None of the six recorded goblets comes close in size to the abovementioned Cologne goblet, but they are nevertheless among the most impressive products of Baroque decorative art. Two of them, formerly in Berlin, were lost during World War II, but the other four are found in public collections in Bremen, Darmstadt, Hamburg, and Corning [Fig. 2 ^^79.3.258^^] (Kerssenbrock- Krosigk 2001, pp. 155–156, nos. 1–6).

Only three vessels offer some clue regarding their date. The covered goblet in Hamburg (Covered ruby goblet. Brandenburg, before 1691. OH. 41.5 cm. Museum für Kunst und Gewerbe, Hamburg (1885.194)) shows the arms of the electors of Brandenburg and Saxony in an arrangement that predates 1691. Stylistically, this glass is very close to the goblet in Corning, of which only the bowl has survived (Fig. 2). A beaker in Copenhagen bears the monogram of Sophia Agnes of Mecklenburg-Schwerin (1625–1694), and another beaker, lost in the war, was inscribed with the initials of Johann Georg II, prince of Anhalt-Dessau (d. 1693).

One notable feature of these vessels is the amount of cut decoration, such as the rows of arches and pointed leaves that were either carved into the glass or left to stand out conspicuously in relief. The evidence that the vessels originated on the glassmaker’s blowpipe is almost entirely veiled: they give the impression that they were not hot-worked but sculpted out of solid stone. Gold ruby and, to a somewhat lesser extent, crystal were understood as new materials, perhaps equivalent to the making of a theretofore unknown semiprecious gemstone, and they were treated accordingly. The contrast with glass in the Venetian style, which emphasized the blown shapes, could not have been stronger.

Colored glass is not an ideal background for intaglio engraving (Tiefschnitt), which is much more effective on colorless crystal. Nevertheless, gold ruby glass was adorned with some of the best engraving on early Brandenburg glass. The putti shown climbing on thick vine scrolls on the Corning goblet [^^79.3.258^^] and the Fruchtkinder (fruit children) with wreaths of fruit depicted on the goblet in Bremen set the standard for Baroque lushness and liveliness, and they can be attributed to the man who was then the best glass engraver in the region, Gottfried Spiller (d. 1728).

With very few exceptions (including two tankards with personifications of the four seasons), engraving on ruby glass ceased in Brandenburg after 1700. In one notable case, the covered goblet with the Brandenburg arms and device in Berlin (Fig. 3. Brandenburg, about 1720. H. 36.5 cm. Kunstgewerbemuseum, Staatliche Museen zu Berlin (W- 1977.84)), the engraving was gilded to heighten the contrast. In most other cases, cutting was employed to fill the spaces that had formerly been reserved for engraving. From a decorative viewpoint, gold ruby remained closer to glyptic art than to glassmaking. The glass cutters, who were entirely anonymous, produced works of exceptional mastery. Seldom has cut decoration been so organically modeled, seemingly floating on the surface, as it appears on the goblet [^^79.3.318^^] and the footed beaker [^^72.3.49^^] in Corning.

Bohemia

The ruby glass made in Brandenburg is unrivaled. Of the more than 30 documented goblets, there is only one that was produced elsewhere (Covered Goblet. Bohemia, probably about 1700. Formerly owned by the counts of Nostitz, Prague. H. 30 cm, D. (foot) 10.8 cm. Collection of the Museum of Decorative Arts, Prague, 78.001). This covered vessel displays all of the characteristic patterns of Bohemian production, and it forms part of a small group, together with a covered beaker (Bohemia, about 1700. OH. 14.3 cm, D. (rim) 7.3 cm. Collection of the Museum of Decorative Arts, Prague, 78.005), two bottles with stoppers (Bohemia, about 1700. Formerly owned by the counts of Nostitz, Prague. H. 15.5 cm, D. (foot) 6.8 cm. Collection of the Museum of Decorative Arts, Prague, 78.011), and a bowl (Kerssenbrock-Krosigk 2001, nos. 39, 95, 352, and 392). A pair of bottles with gilded mounts and screw tops in Berlin’s Kunstgewerbemuseum may have come from the same source (ibid., no. 353. Pair of bottles with gilded mounts and screw tops. Possibly Bohemia, Schlackenwerth, glasshouse of Duke Julius Franz of Saxe-Lauenburg, before 1689. H. 16.9 and 16.5 cm. Kunstgewerbemuseum, Staatliche Museen zu Berlin (W-1962.9, 10)). All of these are true masterpieces. The color is light, tending toward violet, and practically no surface has been left uncut. The workmanship of the faceting is outstanding, and it clearly set a standard for subsequent glass production in Bohemia. The shape of the goblet is related to that of a number of Bohemian colorless glass goblets with spiral gold ruby threads [^^79.3.309^^]. While this confirms the country of origin, the exact source for this group is unknown. The fine execution of the cutting favors a provenance in northern Bohemia, for this was the leading location of the craft.

Kunckel noted that one of his disciples had shared his secrets with Duke Julius Franz of Saxe-Lauenburg, who operated a glasshouse on one of his Bohemian estates, Schlackenwerth (Ostrov, north of Karlsbad [Karlovy Vary]). Julius Franz succeeded in making ruby glass, “whereupon he had [his subjects] sell many such glasses.”22 The duke’s production is also confirmed by inventories made following his death (Kerssenbrock-Krosigk 2001, p. 50). Less is known about the manufacture of ruby glass in the glasshouse of Michael Müller in Winterberg (Vimperk), situated in southern Bohemia. Müller was undoubtedly a highly accomplished glassmaker, and he is said, in a report of 1720, to have introduced the production of ruby glass in his region in 1688.23 As is often the case in the history of glass, the written sources cannot be matched easily with the glass itself, and thus it remains an open question whether the group of known Bohemian gold ruby glass vessels was produced in Schlackenwerth, Winterberg, or another, as yet unknown, place.

Southern Germany

While gold ruby glass from Brandenburg and Bohemia is characterized by superb and extravagant craftsmanship, a major group from southern Germany offers less accomplished but more varied shapes (Kerssenbrock-Krosigk 2002). It consists of beakers, tankards, jugs, ewers, teapots, coffeepots, cups, bowls, boxes, plates, bottles, vases, and many other items.24 All of these share the following features: (1) the glass shapes are relatively simple, (2) the color is a fairly uniform but often streaky raspberry red, and (3) the vessels are frequently mounted in gilded metal. Most of the mounts were made in Augsburg, and if the silver marks are readable, they can be dated fairly precisely. Most of the datable ruby glass mounts were made between 1695 and 1705.

The simple shapes deserve a closer look because they reflect a highly accomplished system of serial production. Evidently, the capabilities of mastering gold ruby glass were limited: not a single goblet made of ruby glass in one piece is known from this region. However, there is a tall goblet in Hamburg’s Museum für Kunst und Gewerbe and another in the Staatliches Museum in Schwerin (Kerssenbrock-Krosigk 2001, pp. 164–165, nos. 40 and 41), and there are some other stemmed vessels that have been assembled from ruby glass parts and metal mounts. The ruby glass parts are found in various contexts. The feet correspond to covers and, when turned upside down, to plates and saucers. The bowls resemble cups and beakers. The knops, which often form part of stems, reappear as cover finials or as little bowls in toilet services. Some shapes could be adapted to serve another function with only minor changes. A globular vessel with a cylindrical neck may have served as a sugar caster, but simply by attaching a handle, it could be turned into a beer mug. If it was given a long spout, it became a coffeepot, and by making the vessel shorter and thicker, it was converted into a teapot.25

Nothing is known about the provenance of these vessels. Their fairly homogeneous appearance indicates a single source of production. The predominantly southern German silver mounts also lead us to assume that they were made in the same region, and for the lack of a better alternative, they have been nicknamed “South German.” However, Kunckel’s description of the duke of Saxe-Lauenburg’s glasshouse, where “many such glasses” were sold, brings this producer into consideration as well. In any case, it is important to note that these objects may have been made in a very short time. A glasshouse that engaged in this production for just a few months and then vanished could easily account for all such vessels that are known today.

Saxony

The Green vault (Grünes Gewölbe) in Dresden houses a tall wineglass (Ruby glass flute with “AR” monogram, about 1715. H. 23 cm. Green Vault, Staatliche Kunstsammlungen Dresden (IV 228)) and four decanters that are made of cased gold ruby glass (Kerssenbrock-Krosigk 2001, pp. 254– 255, nos. 428–431, pls. 15 and 16). The wineglass or Flöte (flute) is made of colorless glass that is covered with a red layer; the cut and engraved decoration thus appears as colorless on the red background. This technique would later become famous and popular in Bohemia, but it was employed here at least a century earlier. The glass is mentioned in the Green Vault inventories of 1725 and 1733, and it may have been made some 10 to 20 years earlier. The flute is unique, since the decanters have an interior ruby layer that was cased with colorless glass; here, the cutting and engraving of the glass had no effect on the color.

Thanks to a contemporaneous report on factories in Saxony, this small and peculiar group of vessels can be linked to Johann Friedrich Böttger (1682–1719), one of the most famous alchemists of the time. The report states:

Thus has he also invented a sort of ruby glass, of which...he himself believes in a letter...of July 30, 1713, that it is the first that has ever been done. But the invention is that the glass is not red throughout, but only on one side, either inside or outside, by which it nevertheless looks as if it were entirely red. However, when engraved on the outside or inside, thereby removing the red skin, the colorless [glass] shines through, and delivers a sight of exceptional beauty.26

Böttger had served his apprenticeship at a pharmacy in Berlin from 1696 to 1701, which he concluded with the experimental transmutation of pennies into gold before an attentive audience. He was then invited by Johann Kunckel to engage in joint experiments, and shortly thereafter he traveled to Wittenberg, in Saxony, to continue his studies. In the meantime, the elector of Brandenburg had been notified of these movements, and he demanded that Böttger be returned to Berlin. This order was thwarted by the elector of Saxony, who took Böttger into protective custody in his Königstein castle. Böttger remained essentially a prisoner for most of the rest of his life, although he was provided with comfortable means for his research. Apart from his alchemical experiments, he joined the mathematician Ehrenfried Walter von Tschirnhaus (1651–1708) in his research on ceramic technology. Tschirnhaus is probably to be credited with the invention of European hard-paste porcelain, but it was Böttger who perfected it shortly after the death of his mentor, and he presented it to the elector and the public in 1709.

Gold ruby glass seems to have been merely a byway for the enigmatic Böttger, but it demonstrates his competence in a wide range of technical and chemical pursuits.

Later Years

Fig. 4. Goblet. Bohemia, Haida, workshop of Friedrich Egermann, about 1845. H. 21.5 cm. The Corning Museum of Glass (79.3.523, gift of The Ruth Bryan Strauss Memorial Foundation).The fascination for gold ruby glass began to decline in the early 18th century. While this glass continued to be made in Brandenburg, the kings of Prussia and other statesmen in Germany favored porcelain instead. At some point, possibly in the 1740s, production of gold ruby was halted. From time to time, there were attempts to revive the material. A group of metal-mounted and extremely thick-walled teapots, probably made in Saxony in the 1750s, is the most fruitful result of such efforts (Kerssenbrock-Krosigk 2001, pp. 107–108 and 224–226, nos. 281–291. See Teapot with “AR” monogram, about 1750. H. 13.8 cm. Green Vault, Staatliche Kunstsammlungen Dresden (NZ 1927/3)).

In the 19th century, a more general interest in gold ruby glass was revived. Several countries established societies for the encouragement of the arts and crafts, and the rediscovery of this glass became the subject of competitions (ibid., pp. 129–130). The first to achieve success was Johann Pohl (1769–1850), an outstanding glass technologist and manager of the Harrach glasshouse in Neuwelt (Nový Svet), northern Bohemia, in 1835.27 Various factories followed suit, but the production of gold ruby glass remained an exceptionally difficult and expensive enterprise. However, knowledge of the subject continued to spread, and the first world’s fair, held in London in 1851, featured displays of ruby glass from English companies such as G. Bacchus and Sons of Birmingham, the Falcon Glassworks of Apsley Pellatt, and W. H., B. and J. Richardson of Wordsley, and from the Baccarat firm in France (ibid., p. 132).

Fig. 5. Drinking glass. Germany, Ehrenfeld, Rheinische Glasshütten-Actien- Gesellschaft, Peter Behrens, about 1901. OH. 15.9 cm. The Corning Museum of Glass (2006.3.71).Somewhat earlier, in the 1840s, the glass decorator Friedrich Egermann (Fig. 4) in Haida (Nový Bor) had invented a method of staining glass surfaces a deep red (ibid., pp. 133–134). This technique was suitable for mass production, and it made use of copper rather than gold. Nevertheless, the color was sufficiently close to that of true gold ruby to eventually drive the latter from the market. It was not until 1888 that gold ruby glass resurfaced—in Ehrenfeld, near Cologne (today, it is part of the city; ibid., pp. 131–132). Here, the Rheinische Glashütten-Actien-Gesellschaft specialized in the revival of historical glass styles, and it offered a series of more or less authentic imitations of Baroque gold ruby goblets.

The German architect and avant-garde designer Peter Behrens (1868–1940) later collaborated with this company on one of the most beautiful sets of drinking glasses (Fig. 5) created in the 20th century (ibid., pp. 142–143). He designed these glasses for his own home in Darmstadt about 1901. The production must have been extremely difficult, and glasses of this type are rare.

Today, gold ruby glass has been modified, and other colorants, such as selenium and certain rare earth elements, have replaced the gold. The story of gold ruby seems to have come to an end, but this unique fusion of gold and glass to create a precious color continues to fascinate.


Dedo von Kerssenbrock-Krosigk
This article was published in Glass of the Alchemists: Lead Crystal–Gold Ruby, 1650–1750 (Corning Museum of Glass, 2008)


1. For a translation and comment on manuscripts in Göttingen, Leipzig, and the Escorial in Madrid, see Sheybany 1967; cf. Kerssenbrock-Krosigk 2001, pp. 13 and 21.
2. Kunckel kept the name of the charlatan secret out of respect for the man’s family, but he has since been identified as Christian Wilhelm Baron von Krohnemann, who made a name for himself at other places but died on a gibbet in Kulmbach in 1686 (Loibl 2000, p. 32). Today, his counterfeit gold is a much sought-after collectible.
3. Biographical publications on Kunckel are numerous. See, for example, Kerssenbrock-Krosigk 2001, pp. 36–40.
4. Leibniz 1710, p. 94: “Erat Kunkelius Serenissimi Electoris Saxoniae Johannis Georgii III Chymicus, & cum Augustus Elector olim arcana quaedam Alchymistica lucrifera possedisse pro certo in illis terris habeatur; scripta, (partim propria Principis manu) quae Dresdae extant, & arcani vestigia habere putantur, fidei Kunkelii credita fuerant, ut tentaret, an aliquid inde exsculpi posset” (Kunckel was a chemist at the court of the Saxon elector Johann Georg III [sic; read II ]. The earlier elector, August, was thought to possess in his lands some profitable alchemical secrets, concerning which writings (partly in the prince’s own hand) that are believed to have references to these secrets have come down to us in Dresden. These were entrusted to Kunckel so that he could try to extract something from them”).
5. A second edition, slightly altered, was published in 1689. According to Kunckel’s comments in book 3, chapters 46 and 53 (pp. 97 and 99), he used the Latin version of Neri’s book for his translation and consulted the Italian version only in cases where he suspected that errors had been made.
6. Kunckel also read Merret’s commentary, to which he sometimes refers, as in book 2, chapter 42: Kunckel 1679, p. 85.
7. Ibid., p. 62: “In diesem Capitel ist der Autor gäntzlich denen Buchstaben nachzufolgen /und giebet dieses eine sehr anmutige Coleur nach dieser Art.”
8. Ibid., p. 114: “Der Autor lehret/bin ich gantz gewiß versichert /daß er es nicht gemacht /er würde es sonst anders befunden und nicht also hier gesetzet haben/ denn es gehet im geringsten nicht an....”
9. Ibid., p. 100: “Lehret der Autor, daß die Composition 18. Tage und Nacht im Ofen stehen soll/welches gantz unnöthig/ sonderlich in unsern Teutschen Glas-öfen/ da es nicht 3. Tag und Nacht stehen darff. Der Megnesia /welche der Autor hie gesetzet /ist auch zuviel....”
10. Ibid., pp. 133–134.
11. The earliest known source is a Bolognese manuscript of the first half of the 15th century that contains segreti per colori (secrets for colors). See Merrifield 1849, v. 2, chap. 277, p. 533; cf. Kerssenbrock- Krosigk 2001, p. 30.
12. The text in the second edition (1661) of L’Arte vetraria is slightly different: “però si esperimenti per prouarlo (but one should experiment to prove it).”
13. Kunckel 1679, comment on book 7, chapter 121, pp. 191–192: “Hier wolte ich gerne einen bessern Modum anzeigen/ und auff eine compendieuse Art das rothe oder Rubin-Glas lehren/wann es nicht vor eine so sonderbare Rarität von meinem Gn. Churfürst und Hn. gehalten würde: Wer es aber etwan nicht glauben will / daß ichs kan / der komme ins künfftige und sehe es bey mir. Wahr ist’s: Es ist itzo noch zu rar, gemein zu machen.”
14. Kunckel himself wrote the draft for this deed of gift, which has survived, together with the final document (Geheimes Staatsarchiv Preußischer Kulturbesitz Berlin). It appears in Schmidt 1914, app. 1, no. 13.
15. Kunckel is probably referring here to measurements that varied from state to state at that time.
16. Kunckel 1716, p. 651: “Darauf ließ der Churfürst zu Cölln hochseligen Andenckens mir ansinnen, ob ich ihme einen rothen Kelch machen könnte, der einen grossen Zoll dick, der Fuß ein sehr dicker Knopff, darein ein Ende vom Kelch, und das ander Ende in den dicken Fuß sollte geschraubet werden, und der Deckel oben mit einem Knopff gleicher Gestalt. Solches nahm ich an, worzu mein hochseliger Churfürst mich sehr animirte, ich sollte nicht nachlassen, um die Ehre zu erhalten, daß das erste rothe Glaß bey uns gemacht würde, es möchte auch kosten was es wollte. Ob mir zwar solches das erste mahl wegen der Dicke, auch daß es egal von Farben seyn sollte, mißgelungen, so brachte ich es doch endlich zuwege, und woge das Glaß, so sehr schön war, bey 24. Pfund, davor ließ mir der hochselige Churfürst von Cölln acht hundert Rthlr baar an Gelde auszahlen, ohne was mein hochsel. Herr mir gnädigst über dieses noch geschencket.” The elector and archbishop of Cologne at that time was Maximilian Heinrich of Bavaria (d. 1688). Cf. Kerssenbrock- Krosigk 2001, p. 64.
17. Nicolai and others 1786, v. 2, p. 824: “Ein schöner Kelch von rothem Glase, in der ehemaligen Fabrik zu Potsdam auf Bestellung des Kurfürsten zu Kölln gemacht.”
18. Cf. a very large covered screw-goblet of later date at the Herzog-Anton- Ulrich-Museum in Brunswick (Dresden, about 1731–1736, OH. 76.5 cm; Haase 1988, p. 318, no. 97), and an earlier, smaller example at the Museum Kunst Palast in Düsseldorf (probably Bohemian, late 17th century; Heinemeyer 1966, p. 109, no. 331).
19. See the December 14, 1649, report of Gottfried Wehen from a glasshouse in Württemberg, Germany, reprinted in Lang and others 2001, pp. 177–178. According to Wehen, the gaffers worked seven hours and then took a rest until the new glass batch was ready to be used.
20. Kunckel 1679, foreword, p. B iii: “eines Glas-Künstlers Sohn / und unter ihnen erzogen /auch von Jugend auff in dieser und allerley andern Feuer-Künsten geübet.”
21. In images, the brightness of the glass is often manipulated, and thus it can be properly assessed only with normal lighting in front of the original object.
22. Kunckel 1716, p. 652: “da er dann viel von dergleichen Gläsern verkauffen ließ.”
23. Report of the captain-general of Winterberg, Johann Georg Fr. Praun, to Prince Adam Franz Carl von Schwarzenberg. See Mareš 1893, p. 197; and Kerssenbrock- Krosigk 2001, pp. 50–52.
24. Some of these glass types were also produced in Potsdam. The simpler shapes, such as cups and saucers, can be especially difficult to distinguish.
25. Good examples of these alterations are found in the collection of the Green Vault, Dresden. See Kerssenbrock-Krosigk 2001, pls. 6–8.
26. Steinbrück 1982, pp. 94–95: “So hat Er auch eine Arth von rubin- Glase erfunden, wovon Er...in seinem Briefe...d[en] 30. Jul[i] 1713 selbst glaubet, daß es das erste, so iemahls gemacht worden. Es bestehet aber die invention darinnen, daß das Glaß nicht durch und durch, sondern nur auf einer Seite, als inwendig oder außerhalb roth ist, wodurch es nichts destoweniger aussiehet, als ob es durchaus roth wäre. Inzwischen aber wenn eüßerlich oder inwendig hinein geschnitten, und dadurch das rothe Haütgen hinweg gethan wird, so scheinet das weiße hervor, und giebt ein extraordinair schönes Ausehen.”
27. For the history of the glasshouses in Harrachsdorf (Harrachov) and Neuwelt (Nový Svet), as well as information on Johann Pohl, see Truitt and Truitt 2005. A major research project by Jan Mergl is under way in Karlovy Vary.

Published on June 17, 2013