FOOTNOTES
[304] Lib. xxxvi. c. 26.
[305] Lib. xxxv. c. 26. and lib. xxxvii. c. 9. The lapis obsidianus, which Obsidius first found in Ethiopia, and made known, is undoubtedly the same as that vulcanic glass which is sometimes called Icelandic agate, pumex vitreus, and by the Spaniards, who brought it from America and California, named galinace.
[306] Historiæ Augustæ Scriptores, in vita Gallieni, cap. 12.
[307] Ib. in Vopisc. vita Saturnini, c. 8.
[308] Strabo, Amst. 1707, 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 oxide, such perhaps as ochre or manganese.
[309] Sen. Op. Lipsii, p. 579.
[310] Hist. Nat. lib. xxxvii. c. 12. A passage in Diodorus Siculus, lib. ii. c. 52, alludes, in my opinion, to this method of colouring by cementation.
[311] Magia Naturalis. Franc. 1591, 8vo, p. 275.
[312] Kunkel’s Ars Vitraria. Nur. 1743, 4to, pp. 98, 101.
[313] Comment. Soc. Scient. Gotting. ii. p. 41.
[314] Montamy von den Farben zuni Porzellan- und Email-malen. Leipsic, 1767, 8vo, p. 82. Fontanieu, p. 16.
[315] [The extensive use of this substance in colouring glass and porcelain has rendered its best and most œconomical preparation a subject of interest both to the chemist and the manufacturer. Although the determination of its true chemical composition has presented obstacles almost insuperable, still many important points with regard to its manufacture have been elucidated. It has been found that the tin salt used in precipitating it must contain both the binoxide and protoxide of tin in certain proportions, and it has been also discovered that the degree of dilution both of the gold and tin solutions exerts a very perceptible influence on the beauty of the preparation. Capaun has examined this latter point with great attention, by testing all the different products as to their power of colouring glass.
The first point to be attained is the preparation of a solution of sesquioxide of tin; and for this purpose Bolley proposes to employ the double compound of bichloride of tin with sal-ammoniac (pink salt). This salt is not altered by exposure to the atmosphere, and contains a fixed and known quantity of bichloride of tin, and when boiled with metallic tin it takes up so much as will form the protochloride; as the exact quantity of the bichloride is known, it is very easy to use exactly such a quantity of tin as will serve to form the sesquichloride. 100 parts of the pink salt require for this purpose 10·7 parts of metallic tin.
Capaun recommends dissolving 1·34 gr. of gold in aqua regia, an excess being carefully avoided, and diluting the solution with 480 grs. of water. 10 grs. of pink salt are mixed with 1·07 gr. of tin filings and 40 grs. of water, and the whole boiled till the tin is dissolved. 140 grs. of water are then added to this, and the solution gradually mixed with the gold liquor, slightly warmed, until no more precipitation ensues. The precipitate washed and dried weighs 4·92 grs. and is of a dark brown colour.
M. Figuier states, as the results of his investigations, that the purple of Cassius is a perfectly definite combination of protoxide of gold and of stannic acid, or peroxide of tin, the proof of which is, that it is instantly produced when protoxide of gold and peroxide of tin are placed in contact.]
[316] The original title runs thus:—De extremo illo et perfectissimo naturæ opificio ac principe terrenorum sidere, auro, et admiranda ejus natura, generatione, affectionibus, effectis, atque ad operationes artis habitudine, cogitata; experimentis illustrata. Hamburgi, 1685, 8vo.
[317] Joh. Molleri Cimbria Literata. Havniæ, 1774, fol. i. p. 88.
[318] Miscellanea Berolinensia, i. p. 94.
[319] The author shows only, in a brief manner, in how many ways this precipitate can be used; but he makes no mention of employing it in colouring glass.
[320] I cannot, however, affirm that the vasa murrhina of the ancients were a kind of porcelain coloured with this salt of gold. This is only a mere conjecture.
[321] Alchymia Andr. Libavii. Franc. 1606, fol. ii. tract. i. c. 34.
[322] See Gotting. Gel. Anzeigen, 1778, p. 177.
[323] 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. R. Antonio Neri, Fiorentino. In Venetia, 1663. The first edition, however, must be older. [It is Florence, Giunti, 1612.—Ed.]
[324] Neri, b. vii. c. 129, pp. 157 and 174.
[325] Amst. 1651, vol. iv. p. 78. Lewis says that Furnus Philosophicus was printed as early as 1648.
[326] Glauber first made known liquor of flint, and recommended it for several uses. See Ettmulleri Opera, Gen. 1736, 4 vol. fol. ii. p. 170.
[327] Lewis, Zusammenhang der Künste. Zür. 1764, 2 vols. 8vo, i. p. 279.
[328] The first edition was printed at Augsburg, in duodecimo, and the same year at Amsterdam. It has been often printed since, as in 1739, in 3 vols. 4to, without name or place.
[329] 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.
[330] See Peter le Vieil’s Kunst auf Glas zu malen, Nuremberg, 1779, 4to, ii. p. 25. 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 often he misrepresents their words.
[331] In what the art of Abraham Helmback, a Nuremberg artist, consisted, I do not know. Doppelmayer, in his Account of the Mathematicians and Artists 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.
[332] Ferber’s Briefe aus Welschland. Prague, 1773, 8vo, p. 114.
[333] The devastations to which the productions of this beautiful art have been subjected are deeply to be regretted. It appears from the interesting Account of Durham Cathedral, published by the Rev. James Raine, that there was much fine stained glass in the fifteen windows of the Nine Altars which
“shed their many-colour’d light
Through the rich robes of eremites and saints;”
until the year 1795, when “their richly painted glass and mullions were swept away, and the present plain windows inserted in their place. The glass lay for a long time afterwards in baskets on the floor; and when the greater part of it had been purloined the remainder was locked up in the Galilee.” And in 1802 a beautiful ancient structure, the Great Vestry, “was, for no apparent reason, demolished, and the richly painted glass which decorated its windows was either destroyed by the workmen or afterwards purloined.” The exquisite Galilee itself had been condemned, but was saved by a happy chance.
[334] In 1774 the French Academy published Le Vieil’s treatise on Glass-painting. He possessed no colour approaching to red, except the brick-red or rather rust-coloured enamel subsequently mentioned in the text, derived from iron.
[335] It appears by a boast of Suger, abbot of St. Denis, which has been preserved, that the ancient glass-painters pretended to employ sapphires among their materials; hence, perhaps, the origin of the term Zaffres, under which the oxide of cobalt is still known in commerce.
[336] Oxide of chromium is now substituted for the copper.
[337] That such was the method in use, an attentive examination of old specimens affords sufficient evidence. One piece that I possess exhibits large bubbles in the midst of the red stratum; another consists of a stratum of red inclosed between two colourless strata: both circumstances plainly point out the only means by which such an arrangement could be produced.
[338] In 1793, the French government actually collected a quantity of old red glass, with the view of extracting the gold by which it was supposed to be coloured! Le Vieil was himself a glass-painter employed in the repair of ancient windows, and the descendant of glass-painters, yet so little was he aware of the true nature of the glass, that he even fancied he could detect the marks of the brush with which he imagined the red stratum had been laid on!
[339] [M. Langlois names the following writers: “Neri en 1612, Handicquer de Blancourt en 1667, Kunkel en 1679, Le Vieil en 1774, et plusieurs autres écrivains à diverses époques, decrivaient ces procédés.” (p. 192.) He fixes the restoration of the art in France at about the year 1800, when Brongniart, who had the direction of the Sèvres porcelain manufacture, worked with Méraud at the preparation of vitrifiable colours, p. 194. Among modern artists he particularly mentions Dihl, Schilt, Mortelègue, Robert, Leclair, Collins, and Willement.]
[340] Bulletin de la Société d’Encouragement pour l’Industrie Nationale, 1826.
[341] Though it is difficult to produce the copper-glass uniformly coloured, it is easy to obtain streaks and patches of a fine transparent red. For this purpose it is sufficient to fuse together 100 parts of crown-glass with one of oxide of copper, putting a lump of tin into the bottom of the crucible. Metallic iron employed in the same way as the tin throws out a bright scarlet, but perfectly opake.
[342] “Dr. Lewis states that he once produced a potfull of glass of beautiful colour, yet was never able to succeed a second time, though he took infinite pains, and tried a multitude of experiments with that view.” Commerce of Arts, p. 177.
[343] [At the recent meeting of the British Association for the Advancement of Science, held at Cambridge (June 1845), M. Splittgerber exhibited specimens of glass into the composition of which gold entered as a chloride. These specimens were white, but upon gently heating them in the flame of a spirit-lamp, they became a deep-red. If again the same reddened glass is exposed to the heat of an oxygen blowpipe, it loses nearly all its colours, a slight pinkiness only remaining.]