Dec. 2, 1886] 



NA TURE 



109 



Let us now examine some effects of uniting metals by 

 fusing them together into what are called alloys ; and, 

 second, the direct influence of a minute quantity of one | 

 metal in changing the mass of another in which it is \ 

 hidden, and causing it to behave in a different way in \ 

 relation to light, and consecjuently to possess a colour 

 different from that which is natural to it ; or the added 

 metal may so change the chemical nature of the metallic 

 mass that varied effects of colour may be produced by 

 the chemical combinations which result from the action 

 of certain "pickling" solutions. This portion of the 

 subject is so large that I can only hope to set before you 

 certain prominent facts.' 



First, with reference to the colour produced by the 

 union of metals. Here is amass of red copper, and here 

 one of gray antimony : the union of the two by fusion 

 produces a beautiful violet alloy when the proportions are 

 so arranged that there is 51 per cent, of copper and 49 

 per cent, of antimony in the mixture. This alloy was 

 well known to the early chemists, but unfortunately it is 

 brittle and difficult to work, so that its beautiful colour 

 can hardly be utilised in art. The addition of a small 

 quantity of tin to copper hardens it, and converts it, from 

 a physical and mechanical point of view, into a different 

 metal. The addition of zinc and a certain amount of lead 

 to tin and copper confers upon the mettal copper the 

 property of receiving, when exposed to the atmosphere, 

 varying shades of deep velvety brown, characteristic of 

 the bronze which has from remote antiquity been used 

 for artistic purposes. But by far the most interesting 

 copper alloys, from the point of view of colour, are those 

 produced by its union with zinc, namely brass. Their 

 preparation demands much care in the selection of the 

 materials, and I might have borrowed from the manufac- 

 ture of brass instance after instance of the influence of 

 traces of impurity in affecting the properties of the alloy, but 

 it is unnecessary to dwell upon this alloy in Birmingham, 

 for in all that relates to the mechanical manipulation of the 

 alloys of copper with tin and with zinc, you are masters. 

 I have many inducements in this place to speak about 

 this beautiful alloy. I am proud to Ise a namesake of the 

 craftsman, William Austen, who, in 1460, made that 

 magnificent monument in brass which covers the remains 

 and commemorates the greatness of Richard Beauchamp, 

 Earl of Warwick, and I am glad to remember that Queen 

 Elizabeth granted the first patent for the manufacture of 

 brass in England to William Humfrey, Assay Master of 

 the Mint, a predecessor in the office it is my privilege to 

 hold. 



I want, however, to direct your attention to-night to some 

 alloys of copper with which you are probably less familiar 

 than with brass. In this direction Japanese art affords a 

 richer source of information than any other. Of the very 

 \aried series of alloys the Japanese employ for art metal- 

 work, the following may be considered to be the most 

 important and typical. The first is called '' shaku-do " ; it 

 contains, as you will observe from Analyses I. and II.,- in 

 Shaku-dd. 

 I. II. 



99-89 



addition to about 95 per cent, of copper, as much as 

 4 per cent, of gold. It has been used for very large 



^ h list of books and papers dealing with the colours of metals and alloys, 

 and with the production of coloured patina, is given by Prof. Ledebur in his 

 wirlc "Die Metallverarbeilung," p. 285, 1882, published in Bolley's 

 " Technologic.-' 



= Analyses Nos. I. and III. are by Mr. Gowland. of the Imperial 

 Japanese ftiint at Osaka; Nos. II. and IV. by Prof. Kalischer, Dingl. 

 Potyt. Journ.j ccxv. 93. 



works. Colossal statues are made of it ; one cast at 

 Nara in the seventh century being specially remarkable. 

 The quantity of gold is, however, very variable ; speci- 

 mens 1 have analysed contained only 1-5 per cent of the 

 precious metal. The next alloy to which I would direct 

 your attention is called " shibu-ichi." There are numerous 

 Shibu'ichi. 



99-90 100-15 



varieties of it, but in both these alloys, shaku-do and shibu- 

 ichi, the point of interest is that the precious metals are, 

 as it were, sacrificed in order to produce definite results ; 

 gold and silver, when used pure, being employed very 

 sparingly to heighten the general effect. In the case of 

 the shaku-do, we shall see presently the gold appears to 

 enable the metal to receive a beautiful rich purple coat or 

 patina, as it is called, when treated with certain pickling 

 solutions ; while shibu-ichi possesses a peculiar silver- 

 gray tint of its own, which, under ordinary atmospheric 

 influences, becomes very beautiful, and to which the 

 Japanese artists are very partial. These are the principal 

 alloys, but there are several varieties of them, as well as 

 combinations of shaku-do and shibu-ichi in various propor- 

 tions, as, for instance, in the case of kiu-shibu-ichi, the 

 composition of which would correspond to one part o 

 shaku do rich in gold, and two parts of shibu-ichi rich in 

 silver. Interesting effects are produced by pouring two 

 alloys of different tints together just at the solidifying 

 point of the less fusible of the two, so that the alloys 

 unite but do not blend, and a mottled surface is the 

 result. These alloys are introduced into almost every 

 good piece of metal-work. 



Now as to the action of pickling solutions. Many of 

 you will be familiar with the mysteries of the treatment 

 of brass by "dipping" and " dead dipping," so as to pro- 

 duce certain definite surfaces, but the Japanese art metal- 

 workers are far ahead of their European brothers in the 

 use of such solutions. 



The South Kensington Museum contains a very valu- 

 able series of fifty- seven oblong plates, some plain and 

 others richly ornamented, which were specially prepared 

 as samples of the various metals and alloys used by the 

 Japanese. The Geological Museum in Jermyn Street has 

 a smaller, but very instructive, series, of twenty-four 

 plates presented by an eminent metallurgist, the late M. 

 Hochstatter-Godfrey. From descriptions accompanying 

 the latter, and from information I have gathered from 

 certain Japanese artificers now in London, it would appear 

 that there are three solutions generally in use. They are 

 made up respectively in the following proportions, and 

 are used boiling. 



I. 11. in. 



Verdigi-is 43S grains 87 grains 220 grains 



Sulphate of copper 292 ,, 437 ,, 5^0 ,, 



Nitre — 87 ,, — 



Common salt ... — 146 ,, — 



Sulphur — 233 ,, — 



Water i gallon — i gallon 



Vinegar — i gallon 5 fluid drachms 



That most widely employed is No. I. When boiled in No. 

 III. solution, pure copper will turn a brownish red ; and 

 shaku-do, which, you will remember, contains a little gold, 

 becomes purple ; and now you will be able to appreciate 

 the cftect of small quantities of metallic impurity as 

 affecting the colour resulting from the action of the 

 pickle. Copper containing a small quantity of antimony 

 gives a shade very different from that resulting from the 

 pickling of pure copper. But the copper produced in 

 Japan is the result of smelting complex ores, and the 



