﻿402 Intelligence and Miscellaneous Articles. 



a dark and dirty appearance like that of cast iron. The desire to 

 remedy this led the Berlin Verein zur Beforderung des Gewerbfleisses 

 to cause comparative experiments to be made with a view to find, if 

 possible, a remedy. 



First of all the question had to be solved, whether the production 

 of a beautiful patina is dependent upon the composition of the 

 bronze. For this purpose ten samples of bronzes, remarkable for 

 their beautiful patina and taken from different places, were ana- 

 lyzed. Each of the samples was divided into two, and intrusted to 

 two different chemists. The results were given in the Proceedings 

 of the Verein for the year 1864. They showed that the bronzes in- 

 vestigated were of very varying composition. The proportion of 

 copper varies between 94 and 77 per cent. The quantity of tin 

 amounts in one to 9 per cent., in others to only four ; while others, 

 again, only contain 0*8 per cent., but up to as much as 19 per cent, 

 of zinc. The other accidental admixtures, such as lead, iron, 

 nickel, vary in like manner. With the most different composition 

 these bronzes have all a very beautiful green patina. The com- 

 position may possibly have some influence on the time requisite for 

 the production of the patina ; but the experiments leave no doubt 

 that it ensues even with the most different composition. 



To ascertain the effect of other influences, a number of bronze 

 busts were placed in a part of the town in which particularly 

 unfavourable exhalations take place, and in which various bronze sta- 

 tues in the neighbourhood are destitute of any trace of patina, but 

 have the above-mentioned unpleasant black exterior. 



It was observed that, on several monuments in places accessible to 

 the public, the parts liable to be handled had, if not a green, an 

 otherwise beautiful patina, while all the other parts were black and 

 unsightly. This led the Commission to the idea that grease pro- 

 bably influenced the production of the patina. Hence one of the 

 busts was rinsed every day, with the exception of rainy days, and 

 was, moreover, once a month painted over with bone-oil, which was 

 immediately rubbed off with woollen cloths. Another bust was 

 washed daily with water, but was not oiled. A third, which was 

 also cleaned daily with water, was only oiled twice a year. The 

 fourth was left unpurified, and, indeed, was not at all touched. 



The first- and the last-named bust have been set up since 1864, 

 and treated in the manner described ; the second and third since 

 .1866. The supposition as to the action of the fat has been most 

 completely confirmed. 



The one which has been oiled once a month possesses a dark 

 green patina, which is considered to be very beautiful by all con- 

 noisseurs. The one which is only rubbed twice a year does not look 

 so well ; and that only cleansed with water has none of the beau- 

 tiful appearance which bronzes obtain by the deposit of patina. 

 The one which was not at all cleansed is quite dull and black. 



Hence we may expect that if a bronze exposed in the open air, 

 after being purified, be rubbed down with oil, it will assume a beau- 

 tiful patina. 



How far this rubbing, which in many cases will be difficult to 



