A History of Inventions and Discoveries: Coloured Glass. Artificial Rubies.

A History of Inventions and Discoveries.
By John Beckmann,
Public professor of economy in the University of Gottingen.
Translated from the German, by William Johnston.
Third edition, carefully corrected, enlarged by the addition of several new articles.
In four volumes.
Vol. 1.
Printed for Longman, Hurst, Rees, Orme, and Brown; Baldwin, Cradock, and Joy; R. Priestley; R. Scholey; T. Hamilton; W. Otridge; J. Walker; R. Fenner; J. Bell; J. Booker; E. Edwards; and J. Harding.

* Maximus tamen honos in candido translucentibus, quam proxima crystallii similitudine. Plin. lib. xxxvi. c. 26
*2 Ibid.
*3 Lib xxv. c. 26. and lib xxvii. c. 9. The lapis obvidianus, which Obsidius first found in Ethiopia, and made known, is undoubtedly the same as the volcanic glass which is sometimes calledIcelandicagate, pumez vitreus, and by the Spaniards, who brought it from America and California, named galinace. Thick pieces of it are opake [opale?], but in thin pieces are transparent. The colour of it is generally very black, but in thin pieces it is only blackish and almost like the dark topaz. Sometimes it is also blue, which is often the case in the Venetian. On the sea-coast near Algiers, some pieces of it are found green. The Carpathian mountains produce all kinds of it. See my Physikalisch-ökon. biblioth. iv. p. 29. v. p. 241, and vi. pp. 182, 371.
*4 Idem, cum quidam gemmas vitreas pro veris vendidisset ejus uxori, atque illa, re prodita, vindicari vellet, surripi quasi ad leonem venditorem jussit, deinde e cavea caponem emitti: mirantibusque cuntis rem tam ridiculam, per curionem dici jussit, Imposturam fecit et passus est; deinde negotiatorem dimisit. Historieæ Auguste scriptores, in vita Gallieni, cap. 12.
*5 Adrian in his letter writes as follows: Calices tibi allossontes versicolores transmisi, quos mihi sacerdos templi obtulit, tibi et sorori meæ specialiter dedicatos, quos tu velim festis diebus conviviis adhibeas. Vopiscus in vita Saturnini, c. 8
*6 --- Strabo. Amstelod, apod Wolters 177, fol. lib. xvi. p. 1099. - Some consider the glass earth here mentioned as a mineral alkali, that was really found in Egypt, and which served to make glass; but, as the author speaks expressly of coloured glass, I do not think that the above salt, without which no glass was then made, is what is meant; but rather a metallic earth, such perhaps ochre or manganese.
It is probable that there was no great interval between the discovery of the art of making glass and that of giving it different colours. When the substance of which it is formed, contains, by accident, any metallic particles, the glass assumes some tint; and this happens oftener than is wished; nay, a considerable degree of foresight is necessary to produce glass perfectly colourless; and I am of opinion that this skill has not been attained till a late period in the progress of the art. Even in Pliny's time the highest value was set upon glass entirely free from colour, and transparent, or, as it was called, crystal.* From the different colours which glass acquired of itself, it was easy to conceive the idea of giving it the tinge of some precious stone: and this art, in ancient times, was carried to a very great extent. Proofs of this may be found in Pliny,*2 who, besides others, mentions artificial hyacinths, sapphires, and that black glass which approached very near to the obsidian stone, and which in more than one place he calls gemmæ vitreæ.*3 Trebellius Pollio relates in how whimsical a manner Gallienus punished a cheat who had sold to his wife a piece of glass for a jewel: *4 and Tertullian ridicules the folly of paying as dear for coloured glass as for real pearls. The glass-houses at Alexandria were celebrated among the ancients for the skill and ingenuity of the workmen employed in them. From these the Romans, who did not acquire a knowledge of that art till a late period, procured for a long time all their glass ware. The learned author of Reserches sur les Egyptiens et les Chinois, in the end of his first volume, relates more of these glass-houses than I know where to find in the works of the ancients; but it is certain that coloured glass was made even in those early ages. The emperor Adrian received as a present from an Egyptian priest, several glass cups which sparkled with colours of every kind, and which, as costly wares, he ordered to be used only on grand festivals. *5 Strabo tells us, that a glass-maker in Alexandria informed him that an earth was found in Egypt, without which the valuable coloured glass could not be made.*6

Excidit perro vobis eundem Democritum invenise quemadmodum ebur poliretur, quemadmodum decoctus calculus in smaragdum converteretur, qua hodieque coctum inventi lapides coctiles colorantur. Edit. Lipsii, p. 579.
*2 Quin immo etiam commentarii auctorum, quos non equidem demonstrarim, quibus modis ex crystallo tinguntur smaragdi, aliacque translucentes, sardonix e sarda, etiam ceteræ ex aliis. Neque est ulla fraus vitæ lucrosior. Lib. xxxvii. c. 12. A passage in Diodorus Siculus, lib . ii. c. 52. alludes, in my opinion, to this method of colouring by cementation.
*3 Magia naturalis. Franc. 1591, 8vo. p.275.
*4 Kunkel's Ars vitraria. Nuremberg. 1743, 4to. pp. 98, 101.
Seneca, in his ninetieth epistle, in which he judges too philosophically, that is, with too little knowledge of the world, in regard to the value of labour, mentions one Democritus who had discovered the art of making artificial emeralds; * but in my opinion this discovery consisted in giving a green colour by cementation to the natural rock crystal: and this art I imagine was treated of in that book, the name of which Pliny, through and over anxious care lest the deception should become common, does not mention. *2 For colouring crystal and glass, so as to resemble stones, Porta, *3 neri, *4 and others have, in modern times, given directions which are, however, not much used, because the crystal is thereby liable to acquire so many flaws that it cannot be easily cut afterwards, though, as Neri assures us, these by attention may sometimes be avoided.

* Dissertatio glyptographics, sive Gemmæ duæ vetussimæ - quæ extant Romæ in Museo Victorio, Romæ 1739, 4to. pp. 105, 106.
*2 De cæruleo materiarum vitro æmularum in antiquis monumentis obviarum colore, in Commentationibus Societ. Scient. Gottingensis, ii. p. 41. A translation of this dissertation may be seen in the fifth part of Crell's Chemical Journal.
*3 Montamy von den farben zum porzellan- und email-malen. Leipsig 1767, 8vo. p. 82. Fontanieu, p. 16.
*4 Some excellent remarks respecting the preparation of this goldpurple, which is rather difficult, may be found in L'art de faire les cristaux colorés imitans les pierres précieuses, par M. Fontanieu, Paris 1778, 8vo. p. 11. Lewis, Zusammenhang der künste. Zürich 1764, 8vo. i. p. 276. Baume, Experimental Chemie, iii. pp. 87, 109, 309. The latter gives a different method of preparing the gold, which he calls reducing it to a calx by quick-silver.
It is worthy of remark, that in some collections of antiquities in Rome, there are pieces of coloured glass which were once used as jewels. In the Museum Victorium, for example, there are shown a chrysolite and an emerald, both of which are so well executed, that they are not only perfectly transparent and coloured throughout, but neither externally nor internally have the smallest blemish; which certainly could not be guarded against without great care and skill.*

What materials the ancients used for colouring glass, has not been told to us by any of their writers. It is, however, certain that metallic calces only can be employed for that purpose, because these pigments withstand the heat of the glass furnaces; and it is highly probable that ferruginous earth, if not the sole, was at least the principal substance by which not only all shades of red, violet, and yellow, but even a blue colour, could be communicated, as professor Gmelin has shown.*2 Respecting the red, of which only I mean here to speak, there is the less doubt, as, at present, sometimes an artificial, and sometimes a natural iron ochre is often employed for that purpose. For common works this is sufficient; but when pure clear glass, coloured strongly throughout with a beautiful lively red, free from flaws, and in somewhat large pieces, is required, iron is not fit, because its color, by the continued heat necessary for making glass, either disappears or becomes dirty and almost blackish.*3
In the last century, some artists in Germany first fell upon the method of employing gold, instead of iron, and of thereby making artificial rubies, which, when they were well set could deceive the eye of a connoisseur, unless he tried them with a diamond or a file. The usual method was to dissolve the gold in aqua regia, and to precipitate it by a solution of tin, when it assumed the form of a purple-coloured powder. This substance, which must be mixed with the best frit, is called the precipitate, or gold-calx, of Cassius, gold-purple, or mineral-purple. *4

*The original title runs thus: De extremo illo et perfectissimo naturæ opificio principe terrenorum sidere, auro, et admiranda ejus natura, generatione, affectionibus, effectis, alqua ad operationes artis habitudine, cogitata; experimentis illustrata. Hamburgi 16885, 8vo.
*2 John Molleri Cimbria literata. Havniæ 1774, fol. i. p. 88.
*3 Miscellana Berolinensia, i. p. 94.
*4 We find nothing nmore than the following words: Est tamen modus adhuc alus, quique hactenus secretior fruit, quo, per singularem auri mediante liquore Jovis præcipitationem, sulphur ejus fixum eleganter extravertitur. The author shows only, in a brief manner, in how many ways this precipitate can be used: but he makes no mention of the employing it in colouring glass.
*5 I cannot, however, affirm that the vasa murrhina of the ancients were a kind of porcelain coloured with this calx of gold. This is only a mere conjecture, to be seen in Oeuvres de M. Bosc d'Antic. Paris 1780, 2 vol. 12 mo. i. p. 230.
This Cassius, from whom it takes its name, was called Andrew, and because both the father and son had the same christian name, they have been often confounded with each other. The father was secretary to the duke of Schleswif, and is not known as a man of letters: but the son is celebrated as the inventor or preparer of the gold-purple, and of a bezoar-essence. He took the degree of doctor at Leyden, in 1632, practised physic at Hamburg, and was appointed physician in ordinary to the bishop of Lubec. As far as I know, he never published any thing respecting his art; nut this service was rendered to the public by his son, who was orn at Hamburg, and resided as a physician at Lubec. He was the author of a well-known treatise, now exceedingly scarce, entitled: Thoughts concerning that last and most perfect work of nature, and chief of metals, gold, its wonderful properties, generation, affections, effects, and fitness for the operations of art; illustrated by experiments.*

From this work it will be easily understood why the author does not give himself out as the invertor of the gold-purple, *2 which he is commonly supposed to be, at which Lewis is much astonished. It is seen also by it that Leibnitz calls him improperly a physician at Hamburg, having probably confounded the father and son together. *3 Upon the whole, it is not proved that any of the Cassius's was the inventor of the above precipitate, else it would certainly not have been omitted *4 in this treatise; and mention of gold-purple is to be found in the works of several old chemists.*5

*Rubini frequentes sunt circa montem piniferum, ubi et auri venæ. Consentaneum est, principis auri ibi degenerare in hanc gemman. Ex tinctura auri rubea in liquorem seu oleum soluta, et crystalli liquore potissimum, non incommode fieri posse judicaverim. Alchymia Andræ Libavii. Franc. 1606, fol. ii. tract. i. e. 34. p. 88.
*2 See Gotting. Gel. Anzeigen, 1778, p. 177.
*3 It is well known that Neri's works are translated into Kunkel's Ars vitraria; the edition of which published at Nuremberg in 1743 I have in my possession. The time Neri lived is not mentioned in the Dictionary of Learned Men; but it appears, from the above edition of Kunkel, that he was at Florence in 1601, and at Antwerp in 1609. The oldest Italian edition of his works I have ever seen is L'arte vetraria - del R. P. Antonio Neri, Fiorentino. In Venetia 1663. The first edition, however, must be older.
Something of this kind has, doubtless, been meant by the old chemists, when they talk of red lions, the purple sould of gold, and the golden mantle; but what they wished to conceal under these metaphors, I am not able to conjecture. In the year 1606, when Libavius published his Alchemy, the art of making ruby-glass must have been unknown. He indeed quotes an old receipt for making rubies; and conjectures, that because the real stones of the same name are found in the neighbourhood of gold mines, they may have acquired their colour from that metal; and that, by means of art, glass might be coloured by a solution of gold. * The later chemists, however, and particularly Achard, found no traces of gold, but of iron in that precious stone.*2 The idea which Libavius conceived from a false deduction, has nevertheless been confirmed by experience.

Neri, who lived almost at the same time as Libavius;*3 was better acquainted with the gold-purple, though his receipt is very defective. According to his directions, the gold solution must be evaporated, and the residue suffered to remain over the fire until it becomes of a purple colour.

* Neri, b. vii. e. 129, pp. 157 and 174.
*2 I am acquainted with the Amsterdam Latin edition of 1651, in four small volumes, octavo, where the passage to which I allude is to be found in vol. iv. p. 78. In the common German edition, Glauberi Opera Chymica, Franc. 1658 and 1659, 2 vol. quarto, it is in vol. ii. pp. 125, 343. Lewis says, that Furnus Philosophicus was printed as early as 1648.
*3 Glauber first made known liquor of flint, and recommended it for several uses, as Ettmuller says in Collegium pharmaceus. See M. Ettmulleri Opera, Genevæ 1736, 4 vol. fol. ii. p. 170.
One may readily believe that this colour will be produced; but glass will scarcely be coloured equally through by this powder, and perhaps some of the gold particles will show themselves in it. Kunkel affirms, and not without reason, that something more is necessary to make rubies by means of gold; but he has not thought proper to tell us what it is.*

Glauber, who wrote his Philosophical Furnace*2 about the middle of the 17th century, appears to have made several experiments with the gold-purple. He dissolved the metal in aqua-regia; precipitated it by liquor or flint, and melted into glass the precipitate, which contained in it abundance of vitreous earth.*3

* Nicolai Beschreibung der Residenzstädte Berlin und Potsdam, ii. p. 993.
*2 Lewis, Zusammenhang der Künste. Zürich 1764, 2 vol. octavo, i. p. 279.
*3 The first edition was printed in Augsburg, in duedecimo, and the same year at Amsterdam. It has been often printed since, as in 1739, 3 vol. quarto, without name or place.
None, however, in the 17th century, understood better the use and preparation of gold-purple than John Kunkel, who, after being ennobled by Charles XI, king of Sweden, assumed the name of Löwenstiern. He himself tells us, that he made artificial rubies in great abundance, and sold them, by weight, at a high price. He says, he made for the elector of Cologne a cup of ruby glass, weiging not less than twenty-four pounds, which was a full inch in thickness, and of an equally beautiful colour throughout. He employed himself most on this art after he engaged in the service of Frederic William elector of Brandenburg, in the year 1679. At that time he was inspector of the glasshouses at Potsdam; and, in order that the art of making ruby-glass might be brought to perfection, the elector expended 1600 ducats. A cup with a cover, of this manufacture, is till preserved at Berlin. * Kunkel, however, has no where given a full account of this art. He has only left in his works a few scattered remarks, which Lewis has collected.*2

In the year 1684, earlier than Cassius, John Christian Orschal wrote his well-known work Sol sine veste,*3 in which he treats, more intelligibly than any one before him, of the manner of making ruby-glass. He, however, confesses that Cassius first taught him to precipitate gold by means of tin; that Cassius trated in glass coloured with this precipitate, and that a god deal of coloured glass was then made at Freysingen, but that the art was kept very secret. As Orsschal deserves that his fate should be better known, I shall here mention the following new particulars respecting him. About the year 1682 he was at Dresden, in the service of John Henry Rudolf, from whom he learned many chemical processes, and particularly amalgamation, by which he gained money afterwards in Bohemia.

* So we are told in J. H. Rudolf's Dresdensis Elements Amalgamationis, first printed at Arnstadt in 1712, 4to.
*2 A French translation of Orschal and Grummet is added to l'Art de la verrérie de Neri, Merret, et Kunkel. Paris 1752, 4to. The editor is the baron de Holbach, who, however, has not put his name to the work.
After this he was employed at the mines in Hesse; but he brought great trouble upon himself by polygamy and other irregularities, and died in a monastery in Poland.*

Christopher Grummet, who was Kunkel's assistant, wrote, in opposition to Orschal, his known treatise Son non sine veste, which was printed at Rothernburg, in 1685, in duodecimo.*2 In like manner, an anonymous author printed against Orchal, at Cologne, in 1634, another work, in duodecimo, entitled Apelles post tabulam observans maculas in Sole sine veste. The dispute, however, was not so much concerning the use of gold-purple, as the cause of the red colour, and the vitrification of gold.

* Nicolai, ut supra.
*2 See Peter le Vieil's Kunst auf glas zu malen, Nurenberg 1779, 4to. ii. p25. This singular performance must, in regard to history, particularly that of the ancients, be read with precaution. Seldom has the author perused the works which he quotes; sometimes one cannot find in them what he assures us he found, and very ofthen he misrepresents their words.
*3 In what the art of Abraham Helmback, a Nuremberg artist, consisted, I do not know. Doppelmeyer, in his Account of the mathematicians and artits of Nuremberg, printed in 1730, says that he fortunately revived, in 1717, according to experiments made in a glass-house, the old red glass; the proper method of preparing which had been long lost.
*4 Ferber's Briefe aus Welschland. Prague 1773, 8vo. p. 114.
It is worthy of remark, that Kunkel affirms he could give to glass a perfect ruby.red colour without gold; which Orschal and moset chemists have however doubted. It is nevertheless said, that Krüger, who was inspector of the glass-houses at Potsdam, under Frederic William king of Prussia, discovered earlier the art of making ruby-glass without gold, and that a cup and cover of cut glass made in this manner is still preserved at Berlin.*

Painting on glass and in enamel, and the preparation of coloured materials for mosaic work, may, in certain respects, be considered as branches of the art of colouring glass; and in all these a beautiful red is the most difficult, the dearest, and the scarcest. When the old master-pieces of painting on glass are examined, it is found either that the panes have on one side a transparent red varnish burnt into them, or that the pieces which are stained through and through, are thinner than those coloured in the other manner. *2 It is, therefore, extremely probable, that the old artists, as they did not know how to give to thick pieces a beautiful transparent red colour, employed only iron, or manganese, which pigment, as already observed, easily becomes in a strong heat blackish and muddy.*3 Enamelpainters, however, were for a long time obliged to be contended with it. A red colour in mosaic work is attended with less difficulty, because no transparency, nay rather opacity, is required. At Rome those pieces are valued most which have the beautiful shining red colour of the finest sealing-wax. We are told by Ferber that such pieces were, at one time, made only by a man named Mathioli, and out of a kind of copper dross; at present there are several artists in that city who prepare these materials, but they are not able to give them a perfect high colour.*4

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