The consumption of lampblack is very extensive in common painting, It serves to modify the brightness of the tones of the other colors, or to facilitate the composition of secondary colors. The oil paint applied to iron grates and railing, and the paint applied to paper snuff-boxes, to those made of tin-plate, and to other articles with dark grounds, consume a very large quantity of this black. Great solidity may be given to works of this kind by covering them with several coatings of the fat turpentine, or golden varnish, which has been mixed with lampblack, washed in water, to separate the foreign bodies introduced into it by the negligence of the workmen who prepare it.
After the varnish is applied the articles are dried in a stove by exposing them to a heat somewhat greater than that employed for articles of paper. Naples yellow, which enters into the composition of black varnish, is the basis of the dark brown observed on tobacco-boxes of plate-iron, because this color changes to brown when dried with the varnish.
_To make a Superior Lampblack._
Suspend over a lamp a funnel of tin plate having above it a pipe to convey from the apartment the smoke which escapes from the lamp. Large mushrooms, of a very black, carbonaceous matter, and exceedingly light, will be formed at the summit of the cone. This carbonaceous part is carried to such a state of division as cannot be given to any other matter, by grinding it on a piece of porphyry.
This black goes a great way in every kind of painting. It may be rendered drier by calcination in close vessels.
The funnel ought to be united to the pipe, which conveys off the smoke, by means of wire, because solder would be melted by the flame of the lamp.
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