Arrowsmith, Henry William / The house decorator and painter's guide; containing a series of designs for decorating apartments, suited to the various styles of architecture
[Interior decoration, continued], pp. 33-35
35 Blue colour was first manufactured at Alexandria, and afterwards by Ves- torius, at Puzzuoli. Vitruvius has explained the manner in which it was made in his own day. With the flower of sulphur a quantity of sand was ground until reduced to a fine powder, when filings of Cyprian copper were added, and the whole brought to a paste by being mixed with water. In this state the composition was moulded into balls, and exposed to intense heat in a furnace, by which means the copper and sand " imparted to each other their different qualities and their blue colours." In examining the methods of manufacture adopted by the ancients, from the few scanty notices which are left for us, chiefly by Vitruvius, from whose writings nearly all the facts here stated are obtained, we are particularly struck with the extreme simplicity of the contrivances employed, and the accuracy of the information, although unconnected with any sound scientific principle. The facts known to the Romans and other ancient nations, were the result of fortuitous circumstances, and not of inductive reasoning, as in the present d&y. Still the reader must be interested by the inventions already mentioned; and the ancient process of making white lead is not less worthy of notice. " The Rbodians," says Vitruvius, " place in the bottoms of large vessels a layer of twigs, over which they pour vinegar, and on the twigs they lay masses of lead. The vessels are covered to prevent evaporation; and when, after a certain time, they are opened, the masses are found to be changed into white lead. In the same way they make verdigris, which is called wruca, by means of plates of copper. The white lead is roasted in a furnace, and by the action of the fire becomes red lead. This invention was the result of observation in the case of an accidental fire; and by the process, a much better material is obtained than that which is procured from mines."
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