Fragments of the Firmament: The Mystery of the “Golden Ruby Glass”

(ORDO NEWS) — Golden ruby ​​is perhaps one of the most beautiful glass colors. In addition to its aesthetic qualities, it also has an alchemical connotation: Since the time of ancient Greece, descriptions of the witch’s stone agree that it was considered a red substance and the key to the transmutation of metals, mainly to obtain gold.

The one who discovered the method of staining glass red must have considered himself on the right track to achieve the ultimate goal of alchemy. The 10th-century Persian physician and philosopher Rhazes (circa 865 – between 923 and 935) seems to have thought he had already achieved this goal.

In his formula – the earliest known written record of gold ruby ​​glass – he stated that the glass attracted gold and silver like a magnet, and that it could transform gold 1,000 times its weight.

Approximately 800 years later, the enthusiasm for the golden ruby ​​reached its peak. As far as can be judged from the heritage of princely treasures in today’s public collections, almost every sovereign of Central Europe owned one or more vessels of gold ruby.

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This peak in the popularity of ruby ​​gold goblets occurred in a relatively short period, between about 1685 and 1705.

It was preceded by a long history of development, which culminated in the production of large vessels glowing with a deep but transparent ruby ​​color. In its heyday, ruby ​​gold glass was apparently considered not just a decorative frill, but a truly new and valuable material.

It occupied about the same place as hard porcelain, which appeared in Europe only a few decades later. During the 18th century, interest in the golden ruby ​​persisted in some regions and sporadically in others, but it never gained the widespread recognition it once had.

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The history of the golden ruby ​​has many origins. Red glass has been produced in one form or another almost since the advent of glassmaking.

Knowledge was gained and lost, and although there were several discoveries, this glass does not seem to have been produced 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 Kunkel (1637?-1703; fig. 1) at the beginning of 1678, that the real history of golden ruby ​​glass begins.

JOHANN KUNKEL

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The first appearance of Kunkel at the Brandenburg court of Friedrich Wilhelm (r. 1640-1688), who was called the “great elector”, could not have been more successful. His notes indicate that the prince took a great interest in alchemy and wanted to hear about his experiments.

Soon Friedrich gave him the opportunity to demonstrate his talent. Kunkel was asked to comment on experiments performed by an alchemist who pretended to make gold from silver. Kunkel quickly exposed this ruse, saving the prince from having to spend considerable sums of money on the quackery of the so-called gold miner.

Kunkel’s entry into the life of the court certainly made an impression on the prince, and a few months later, in the summer of 1678, Kunkel became Frederick’s valet and moved to Berlin. He was an extremely suitable choice for the position. The son of a “glass artist”, Kunkel was born in or around Plön, a village southeast of Kiel, in the 1630s.

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In the 1650s he became an apothecary doing alchemical research at Duke Franz-Karl von Saxe-Lauenburg’s castle in Neuhaus, south of Hamburg.

In 1667, Elector Johann George II of Saxony (r. 1656-1680) entrusted him with a difficult task. He was to go through the library of the Elector’s alchemical works and uncover their secrets, mainly concerning the manufacture of gold.

This assignment allowed Kunkel to study virtually all available alchemical knowledge, glean some valuable insights from writers who were seriously interested in chemistry, and develop unrivaled expertise in spotting the frauds of everyone else.

In addition, he conducted his own experiments to evaluate the conclusions contained in his sources. It was probably at this time that he began to apply an empirical, scientific approach to glass production.

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Antonio Neri’s L’Arte vetraria, published in Florence in 1612, is well known to English-speaking readers through an annotated translation made in 1662 by the librarian and naturalist Christopher Merret.

The German version of this influential book, which was prepared by Johann Kunkel under the title Ars Vitraria and first printed at Wittenberg in 1679, received less attention outside of Central Europe.

However, Kunkel not only translated the work, but greatly enhanced its value (Kunckel 1679).5 Unfortunately, although Kunkel translated Merrett’s commentaries into German, an English translation of Kunkel’s edition has not yet been published. Neri collected glass recipes, especially colored glass and enamel paints, and made them public.

Prior to this, collections of glass compositions in manuscript form were a closely guarded secret, and it must have been difficult for Neri to piece together the information he published. Merrett gave an artfully crafted commentary, adding information about the design of the furnace, as well as English raw materials and types of glass.

Kunkel, for his part, commented on the result of each of Neri’s recipes, having tested them all for himself. Often he fully approves of one procedure or another, such as his assessment of blue in book 1, chapter 23: “In this chapter, the author [Neri] must be followed to the letter, and [this recipe] produces a very charming color of this kind.” .

Sometimes, however, he completely rejects the formula, as, for example, in his review of the shade of lapis lazuli in book 4, chapter 72:

“The author shows, I am absolutely sure, that he has not tried it himself, otherwise he would have treated it differently and would have refrained from including it [in the book], because it does not work at all….”.

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Kunkel often gives advice on how to adapt the process to Nordic practices and raw materials. In his comments on the color lattimo (white) in book 3, chapter 55, he says:

“The author teaches that the composition should be kept in the furnace for 18 days and nights, which, however, is completely redundant, especially in our German glass furnaces, where it should be kept for no more than three days and nights. The manganese content that the author uses is also too high ….

“In several cases, he proposes solutions that are completely different from those of his Italian predecessor, as, for example, in book 5, chapter 91.10

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Sixteen of the 133 chapters of Antonio Neri’s book “L’Arte vetraria” are devoted to red glass. Nine of them offer formulas that give more purple or brown color, and they are based on the use of manganese.

The six formulas use copper, which had a long tradition as a dye for red glass in cathedral windows and in the translucent red enamels (rosichiero, or rouge clair) used by goldsmiths in the Middle Ages and the Renaissance.

At the end of Neri’s treatise, one of the recipes mentions the use of gold. This shows that the potential of using gold as a red dye was fully realized in early 17th century Italy. In fact, this knowledge may date back to the 15th century or even earlier.

However, this did not lead to an abundant production of Italian gold ruby. The only known vessels with a golden ruby ​​of Italian origin are a series of ribbed bowls, wine glasses and bottles that King Frederick IV of Denmark brought back from a trip to Venice in 1708-1709 (kept at Rosenborg Castle, Copenhagen).

Neri’s recipe apparently works (it was tested under ideal conditions in 1930), but the author himself was highly dubious and ended his discussion with the remark that “però si esperimenti per trouarlo” (but one must experiment to find it).

Kunkel’s attempts to reproduce the recipe were unsuccessful, and he was misled by a mistranslation from Latin, which turned the clause into its opposite: “ut experimento compertum est” (in Merrett’s 1662 translation, “as established by experience”). In any case, these instructions serve at best to obtain the color of the enamel, and they are certainly not sufficient for full-scale glassblowing.

On only one occasion, in the context of one of Neri’s instructions for ruby-copper glass, did Kunkel remark that he knew a better procedure:

Here I wanted to indicate the best way and briefly teach [making] red or ruby ​​glass, if it were not considered such an unusual rarity by my gracious elector and master. Who does not believe that I can do it, let him come and see. It’s true: it’s still too rare to talk about.

It is possible that Kunkel deliberately chose the commentary on this recipe to talk about his own endeavors, rather than the book’s only formula for the golden ruby, in order to send potential competitors down the wrong path.

A little earlier (in September 1678), in a letter to the Nuremberg physician and scientist Johann Georg Volkamer, he enthusiastically reported that he had found a method for making golden ruby ​​glass (Fetzer 1978, pp. 71-73; cf. Kerssenbrock-Krosigk 2001, p. 42 ).

He did not claim it was his own invention, but instead referred to experiments carried out in Hamburg by the physicist Andreas Cassius (1605-1673), as we learn from Kunkel’s posthumously published Laboratorium Chymicum, in which he offers a detailed account of his golden ruby ​​glass ( Kunckel 1716, pp. 652-655).

Cassius was born in Schleswig, which is not far from the birthplace of Kunkel himself, and graduated from Leiden University.

He created a purple colored solution of gold (Cassius purple) by mixing gold chloride and stannose chloride in aqua regia (HCl/HNO3). His son, also named Andreas (1645 – about 1700), published this method in 1685 (Cassius 1685, chap. 10; translated in Hunt 1976, pp. 138-139, and idem 1981, p. 64).

The purple of Cassius described by Kunckel (1716, pp. 382-383) was not invented by Cassius. Johann Rudolf Glauber described the process in principle as early as 1659 (see pp. 64-65 in The Glass of the Alchemists). It was the ideal raw material for ruby ​​gold glass, as it allowed the gold particles to be obtained in the finest solution.

When the finished product is reheated, metallic gold forms nano-sized particles, which must be of the correct size and shape in order to convey a purplish-ruby color through light absorption.

If the gold colloids, as these particles are called, are too small, the glass remains colorless. If they are too large and absorb too much light, the glass takes on a liver (in German lebrig) or opaque brownish color.

Alchemists and glassmakers of the Baroque period, of course, had no idea about colloidal chemistry, so they had to rely entirely on their own experience. It is one thing to make small samples of a golden ruby ​​in the laboratory, and quite another to blow a uniformly colored vessel out of this glass.

How Kunkel and his craftsman managed to produce the large, impeccably colored goblets of various thicknesses that we admire today remains a mystery.

Kunkel’s unique contribution was the experimental use of the golden ruby ​​in the manufacture of vessel glass. Judging by available sources, he had not yet succeeded in 1679 when he published his Ars Vitraria, but did so no later than 1684 (Kerssenbrock-Krosigk 2001, pp. 41-42).

These efforts did not come cheap. From the materials of subsequent court proceedings it is known that over 10 years of work, Kunkel earned 5,000 Reichsthaler and received another 21,325 Reichsthaler from his patron Friedrich Wilhelm (ibid., pp. 39-40). However, the Elector did not lose his enthusiasm.

In 1685 he gave Kunkel the Pfaueninsel (Peacock Island) on the river Havel between Berlin and Potsdam, one of the most romantic places in northern Germany. there in an attempt to hide it from the eyes of imitators. Further signs of favor from Friedrich Wilhelm were to follow, but the enthusiasm did not last long.

The elector died in 1688, and Kunkel became a target for those who envied his success. His island laboratory was set on fire, and he himself was accused of embezzlement. However, Kunkel remained in Brandenburg for the most part and seems to have continued to make glass.

But he also developed a new scientific passion for mining. This led him to Sweden in 1693, where he tried to improve the method of extracting copper from ore (Selchow 1984). Although this attempt was unsuccessful, nevertheless, Kunkel was given the title of nobility “von Löwenstern”. where he tried to improve the method of extracting copper from ore (Selchow 1984).

Although this attempt was unsuccessful, nevertheless, Kunkel was given the title of nobility “von Löwenstern”. where he tried to improve the method of extracting copper from ore (Selchow 1984). Although this attempt was unsuccessful, nevertheless, Kunkel was given the title of nobility “von Löwenstern”.

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

Then the Elector of Cologne of blessed memory demanded that I make him a red chalice: large, 15 inches thick, the stem is very thick, one end of the chalice was to be screwed into it, and the other end [of the leg] into the thick stem; and a lid with enamel of the same shape [as the leg].

I agreed, to which my late elector [of Brandenburg] strongly urged me: I must not stop to achieve the honor that the first red glass be made here, no matter how much it costs.

Although my first attempt failed due to the thickness, as well as considering that it should be even in color, I eventually succeeded. The glass, which was very beautiful, weighed about 24 pounds. The Elector of Cologne ordered the payment of 800 Reichsthaler in cash, in addition to what my master of blessed memory kindly donated from above.

This event is not dated, but must have taken place around 1684, before Pfaueninsel’s donation. Kunkel wrote his Laboratorium Chymicum some 10 years later, and we may wonder if his account is entirely credible.

The weight in particular seems too much for a baroque glass vessel. On the other hand, this vessel marks an exceptional moment: the beginning of glass production of outstanding quality in Brandenburg.

Ruby gold glass was not only a unique achievement, but also the basis for the creation of a truly exquisite crystal, which could well surpass the quality of glass produced by Kunkel’s competitors in continental Europe.

The goblet, made for the Elector of Cologne, was sold for a price equivalent to Kunkel’s one and a half year’s salary, and, quite possibly, remained a unique work.

Unfortunately, this vessel has been lost and we do not have a picture of it. We only know about it from a report by Friedrich Nicolai in 1786, which mentions “a fine red glass chalice made in a former factory in Potsdam, commissioned by the Elector of Cologne”.

At that time, it was in the possession of Mr. Daum, who owned a residence on the Breitstrasse in Berlin, as well as an estate near Charlottenburg (today it is part of Berlin). No other ruby ​​glass goblet is known, consisting of three parts screwed into each other.

This technique is known, though rare among Bohemian and German flint goblets, and may have been necessary to make the unusually sized ruby ​​gold goblet.

Another aspect of Kunkel’s story is noteworthy: He does not mention a craftsman, but claims to have made the goblet himself. It is an important but often overlooked point that glass making is very different from working on a glass vessel.

Selecting the right raw material, batch mixing and melt control require skills quite different from those involved in blowing and shaping the final product. Even in relatively primitive forest greenhouses, this division of labor was observed, if only for the simple reason that if the glazier were also required to prepare a batch, he would be deprived of the few hours that remained for him to sleep.

Keeping the molten glass hot was a costly task, and the gafters could only rest during periods when the crucibles were replenished.

We know that Kunkel had the chemical knowledge necessary to make a batch. However, it is highly unlikely that he was as skilled with the blowpipe, which requires constant practice. However, Kunkel states that he was “the son of a glass-maker and was educated among them, and was trained in this and various other arts of fire from his youth,”20 and as an alchemist, he was able to make his own glassware.

It is tempting to imagine that Kunkel was actively involved in the formation of some of his gold ruby ​​vessels, especially since the process of making ruby ​​glass did not end with the supply of molten glass, but was completed only after the finished object was reheated. Perhaps this was the decisive problem in the creation of golden ruby ​​glass: a person was required,

Baroque gold ruby ​​glass vessels made in Brandenburg can be divided into two production phases. The first phase began with Kunkel around 1684 and ended during the reign of Elector Frederick III (r. 1688-1713; he was crowned King Frederick I of Prussia in 1701).

We do not know if Kunkel continued to work in this area after the death of his patron, Elector Friedrich Wilhelm, in 1688, and for how long. The second phase began around 1719, during the reign of King Frederick William I (1713-1740), and continued, on a smaller scale, into the 1740s.

The glass of these two phases can be distinguished not only by stylistic features, but also by color: early production has a bright crimson red color, while later glass tends to be darker.21 We know about 22 vessels, goblets and glasses, which can be attributed to Brandenburg before 1700.

None of the six fixed goblets come close in size to the aforementioned Cologne goblet, but they are nonetheless among the most impressive pieces of decorative art from the Baroque era.

Two of them, formerly in Berlin, were lost during the Second World War, but the remaining four are in the public collections of Bremen, Darmstadt, Hamburg and Corning [Fig. 2 ^^79.3.258^^] (Kerssenbrock-Krosigk 2001, pp. 155-156, no. 1-6).

Only three vessels give some clue as to their dating. Indoor cup in Hamburg (Covered ruby ​​cup. Brandenburg, before 1691. OH. 41.5 cm. Museum für Kunst und Gewerbe, Hamburg (1885.194)) shows the coats of arms of the Electors of Brandenburg and Saxony in an arrangement that preceded 1691.

Stylistically, this glass is very close to the Corning goblet, of which only the bowl has survived (Fig. 2). A glass in Copenhagen bears the monogram of Sophia Agnes of Mecklenburg-Schwerin (1625-1694), and another glass, lost during the war, bears the initials of Johann George II, Prince of Anhalt-Dessau (d. 1693).

A notable feature of these vessels is the amount of carved decoration, such as rows of arches and pointed leaves, which were either carved into the glass or left to stand out in relief. The evidence that these vessels were made on a glassblower’s glass blower is almost completely veiled: it seems that they were not hot-worked, but hewn from solid stone.

The golden ruby ​​and, to a lesser extent, crystal were understood as new materials, perhaps equivalent to the manufacture of a hitherto unknown semi-precious stone, and were treated accordingly. The contrast with the Venetian-style glass, which accentuated 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. However, the ruby-gold glass was decorated with some of the finest engravings on early Brandenburg glass.

Putti climbing the thick vine scrolls on a Corning goblet [^^79.3.258^^] and Fruchtkinder (children of fruit) with wreaths of fruit on a Bremen goblet set the baroque standard for pomp and liveliness and can be attributed to a man who at that time was the best glass engraver in the region, to Gottfried Spiller (d. 1728).

With rare exceptions (including two tanks with personifications of the four seasons), ruby ​​glass engraving ceased in Brandenburg after 1700. In one notable case, on a covered goblet with the emblem and device of Brandenburg in Berlin (Fig. 3. Brandenburg, circa 1720.

H. 36.5 cm. Kunstgewerbemuseum, Staatliche Museen zu Berlin (W-1977.84)), the engraving was gilded for contrast enhancement. In most other cases, cutting has been used to fill spaces previously reserved for engraving.

From a decorative point of view, the golden ruby ​​remained closer to glyptic art than to glassmaking. The glass cutters, who were completely anonymous, created works of exceptional craftsmanship. Rarely has carved decoration been so organically modeled, as if floating on the surface, as shown on the goblet [^^79.3.

Ruby glass made in Brandenburg is second to none. Out of more than 30 documented cups, there is only one that was produced elsewhere (Covered cup. Bohemia, probably around 1700. Previously belonged to the counts of Nostitz, Prague. H. 30 cm, D. (stem) 10.8 cm. Collection of the Museum of Decorative Arts, Prague, 78.001).

This covered vessel shows all the characteristic patterns of Bohemian manufacture and belongs to a small group together with a covered glass (Bohemia, circa 1700. OH. 14.3 cm, D. (rim) 7.3 cm.

Collection of the Museum of Decorative Arts, Prague, 78.005 ), two bottles with corks (Bohemia, around 1700. Previously belonged to the counts of Nostitz, Prague. H. 15.5 cm, D. (stem) 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).

Pair of bottles with gold-plated fasteners and screw caps in the Berlin Kunstgewerbemuseum, possibly from the same source (ibid., no. 353. Pair of bottles with gold-plated fasteners and screw caps. Possibly Bohemia, Slakenwerth, conservatory of Duke Julius Franz of Saxe-Lauenburg, until 1689. H. 16.9 and 16.5 cm. Kunstgewerbemuseum, Staatliche Museen zu Berlin (W-1962.9, 10)). All of them are real masterpieces.

The color is light, leaning towards purple, and virtually no surface is left uncut. The quality of the cut is outstanding and it clearly set the standard for subsequent glass production in Bohemia. The shape of the goblet resembles that of a row of Bohemian goblets made of colorless glass with spiral golden ruby ​​threads [^^79.3.309^^].

Although this confirms the country of origin, the exact source of this group is unknown. The fine workmanship of the carving speaks in favor of an origin in northern Bohemia, since this was the leading place for the development of the craft.

Kunkel noted that one of his students shared his secrets with Duke Julius Franz of Saxe-Lauenburg, who maintained an orangery on one of his Bohemian estates, Schlakenwerte (Island, north of Karlsbad [Karlovy Vary]).

Julius Franz succeeded in making ruby ​​glass, “after which he forced [his subjects] to sell many such glasses.”22 The duke’s production is also confirmed by records made after his death (Kerssenbrock-Krosigk 2001, p. 50).

Less is known about the production of ruby ​​glass in the Michael Müller greenhouse in Winterberg (Vimperk), located in the south of the Czech Republic. Müller was undoubtedly a high-class glassmaker, and an account from 1720 states that he introduced the production of ruby ​​glass to his region in 1688.23 As often happens in the history of glass,

South Germany

While ruby ​​gold glass from Brandenburg and Bohemia is distinguished by superb and extravagant craftsmanship, a large group from South Germany offer less perfect but more varied forms (Kerssenbrock-Krosigk 2002). It consists of beakers, tankards, jugs, wine glasses, teapots, coffee pots, cups, bowls, boxes, plates, bottles, vases, and many other items.

24 They all have the following in common: (1) the shapes of the glass are relatively simple, (2) the color is fairly uniform, but often a washed out crimson red, and (3) the vessels are often mounted in gilded metal. Most of the fasteners were made in Augsburg, and if the hallmarks on the silver are legible, they can be dated fairly accurately. Most dated ruby ​​glass fixtures were made between 1695 and 1705.

Simple forms deserve closer attention as they reflect a highly efficient mass production system. Obviously, the opportunities for the development of golden ruby ​​glass were limited: not a single goblet made of ruby ​​glass in a single copy is known from this region.

However, there is a tall goblet in the Hamburg Museum of Arts and Crafts and another in the Schwerin State Museum (Kerssenbrock-Krosigk 2001, pp. 164-165, nos. 40 and 41), as well as several other stemmed vessels assembled from pieces of ruby ​​glass and metal fasteners. Ruby glass details are found in a variety of contexts.

The legs correspond to the lids, and in an inverted form – to plates and saucers. The bowls resemble cups and glasses. The knobs, which are often part of the legs, appear as the tops of lids or small bowls in toilet sets.

Some forms can be adapted to perform a different function with minor modifications. A spherical vessel with a cylindrical neck could serve as a sugar bowl, but by attaching a handle, it could be turned into a beer mug. If you make a long spout, then it turns into a coffee pot, and if you make the vessel shorter and thicker, then it turns into a teapot.

Nothing is known about the origin of these vessels. Their rather uniform appearance indicates a single source of production. The predominantly South German silver fastenings also lead us to assume that they were made in the same region, and for lack of a better option they were called “South German”.

However, Kunkel’s description of the conservatory of the Duke of Saxe-Lauenburg, where “a lot of such glasses” were sold, makes us think about this manufacturer as well. In any case, it is important to note that these items could be made in a very short time.

The greenhouse, which was engaged in this production for only a few months and then disappeared, could easily explain all such vessels known today.

The Green Vault (Grünes Gewölbe) in Dresden contains a tall wine glass (a ruby ​​glass goblet with the monogram “AR”, circa 1715. H. 23 cm. Green Vault, Staatliche Kunstsammlungen Dresden (IV 228)) and four decanters made from ruby gold glasses (Kerssenbrock-Krosigk 2001, pp. 254-255, no. 428-431, pls. 15 and 16).

The wine glass or Flöte (flute) is made of colorless glass coated with a red layer; thus, carved and engraved decorations appear colorless against a red background. This technique would later become famous and popular in Bohemia, but here it had been used at least a century earlier.

Glass is mentioned in the Green Vault inventories of 1725 and 1733, and it may have been made about 10-20 years earlier. The glass is unique since in decanters the inner ruby ​​layer was covered with colorless glass; in this case, the cutting and engraving of the glass did not affect the color.

Thanks to a contemporary account of factories in Saxony, this small and unusual group of vessels can be linked to Johann Friedrich Böttger (1682-1719), one of the most famous alchemists of the time. The report says:

Thus he also invented a kind of ruby ​​glass, which… he himself considers in a letter… dated July 30, 1713, to be the first ever made. But the invention lies in the fact that the glass is not red over the entire surface, but only on one side, either inside or outside, due to which it nevertheless looks like it is completely red.

However, when the engraving on the outer or inner side removes the red shell, the colorless [glass] shines through and is a spectacle of exceptional beauty.

Böttger practiced in a Berlin pharmacy from 1696 to 1701, which he completed by experimentally transmuting pennies into gold before an attentive audience. He was then invited by Johann Kunkel to take part in joint experiments, and shortly thereafter he went to Wittenberg, in Saxony, to continue his studies.

In the meantime, the Elector of Brandenburg was notified of these movements and demanded that Böttger be returned to Berlin. This order was thwarted by the Elector of Saxony, who took Böttger under guard in his castle of Königstein.

For most of his life, Böttger remained essentially a prisoner, although he was provided with convenient facilities for research. In addition to alchemical experiments, he, together with the mathematician Ehrenfried Walther von Tschirnhaus (1651-1708), was engaged in research in the field of ceramic technology.

The ruby ​​gold glass appears to have been only the path of the enigmatic Böttger, but it demonstrates his competence in a wide range of technical and chemical tasks.

Passion for ruby ​​gold glass began to subside at the beginning of the 18th century. Although this glass continued to be made in Brandenburg, the kings of Prussia and other German statesmen preferred porcelain.

At some point, perhaps in the 1740s, the gold ruby ​​was discontinued. From time to time attempts have been made to revive this material. A group of thick-walled metal 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 monogrammed teapot “AR”, circa 1750. H. 13.8 cm Green vault, Staatliche Kunstsammlungen Dresden (NZ 1927/3)).

In the 19th century there was a resurgence of a more general interest in ruby ​​gold glass. Societies for the encouragement of arts and crafts were formed in several countries, and the rediscovery of this glass became the subject of competitions (ibid., pp. 129-130).

The first to succeed was Johann Pohl (1769-1850), an eminent glass technologist and manager of the Harrach greenhouse in Neuwelt (New World), northern Bohemia, in 1835.27 Various factories followed suit, but the production of golden ruby ​​glass remained an exceptionally complex and costly undertaking.

However, knowledge of the subject continued to spread, and the first world exhibition, held in London in 1851, featured ruby ​​glassware from English companies such as G. Bacchus and Sons of Birmingham, Falcon Glassworks of Apsley Pellatt, WH, B. and J.

Somewhat earlier, in the 1840s, the glass decorator Friedrich Egermann (fig. 4) in Heide (Novy Bor) invented a method for painting glass surfaces in a rich red color (ibid., pp. 133-134). This technique was suitable for mass production and used copper rather than gold. However, the color was close enough to that of a real gold ruby ​​that it eventually forced the ruby ​​out of the market.

Only in 1888 in Ehrenfeld, near Cologne (today it is part of the city; ibid., pp. 131-132), gold-ruby glass reappeared. Here the Rhine Society “Glashütten-Aktien-Gesellschaft” specialized in the revival of historical styles of glass and offered a series of more or less authentic imitations of gold ruby ​​goblets from the Baroque period.

The German architect and avant-garde designer Peter Behrens (1868-1940) subsequently 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 created these glasses for his home in Darmstadt around 1901. The production must have been extremely complex and glasses of this type are rare.

Today, ruby ​​gold glass has been modified to use other dyes, such as selenium and some rare earth elements, instead of gold. The history of the golden ruby ​​seems to have come to an end, but this unique fusion of gold and glass to create a precious color continues to fascinate.

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