400 Scientific Intelligence — Arts. 



sign is made in a fit earthy material (being pnzzolana, or one of the 

 volcanic deposites), and this is placed witiiin, and forms part of, the 

 larger iron mould, in which the decanter is blown. When the large 

 mould is removed, the earthen portion still adheres to the glass 

 and continues in its place until the bottle is finished. After the an- 

 nealing, the mould is moistened with water, and immediately sepa- 

 rates, and the impression is found really perfect. — Royal Institution 

 Proceedings. — Athsnceuin, No. 1061, p. 220, February 26, 1848. 



19. House Painting. — M. Leclaire, house-painter, calls the at- 

 tention of the Academy to a substitution which he daily makes of the 

 white of zinc and colours with a zinc base, for white-lead and colours 

 with a base of copper and lead, in the arts, and for ordinary pur- 

 poses. 



In his daily practice, M. Leclaire employs the white of zinc, 

 which appears to possess all the qualities of white-lead, without any 

 of its inconveniences. Thus, if we must give credit to his state- 

 ments, and the results are of sufficient standing to render it easy to 

 verify them, zinc- white is much whiter than white- lead ; ground 

 and used with oil, it reflects the light, instead of absorbing it : it 

 furnishes finer and more transparent tones, it covers better, and 

 with equal weights, a larger space ; it remains unchanged by 

 sulphurous fumes, which immediately blacken objects painted with 

 lead ; finally, the manufacture and use of zinc-white has no in- 

 jurious effect upon the health. But all this is not sufficient for the 

 complete solution of the problem. In fact, although zinc-white 

 was known in science, it has never been collected hitherto but as 

 a produce of the laboratory. It was necessary to obtain it in quan- 

 tities and at an accessible price. Then, once obtained and mixed 

 with oil, it was necessaiy, in order to apply it readily to painting, 

 that it should be made to dry easily. Now, the only drying sub- 

 stances we knew had a leaden base, and thus communicated all the 

 defects of lead to the zinc-white. M. Leclaire has obtained a dry- 

 ing substance with a manganese base, which has the property of 

 drying zinc-white more readily than litharge could do. 



This was not all. White tones form, so to speak, a kind of ex- 

 ception in painting. Some of the colours most in use are extracted 

 from lead and copper, and owe to these metals the defect of being 

 alterable by sulphurous gases ; mingled with zinc-white, they de- 

 prived it of the advantage of being unalterable. It was necessary, 

 therefore, to render the process complete, and its application com- 

 mon, to substitute colours which undergo no change for all these 

 alterable colours. After many years of research, says M. Leclaire, 

 I have succeeded in producing, if I may use such an expression, the 

 commencement of a reformation in painting, by completing the scale 

 of unalterable colours — by the substitution of inoffensive and unalter- 

 able colours for all such as had lead or copper for their base, so that 

 I can now affirm, 1st., That the health ol a great number of men 



