Important: Safety Warning
This page contains instructions involving gunpowder or other explosive or pyrotechnic compositions. Preparing explosives as described has caused severe injuries and deaths, and is illegal in most places.
In addition, this page describes trade processes that use dangerously toxic materials such as cyanide solutions, mercury amalgams, or strong acids. These processes require training, equipment, and precautions far beyond what the text describes.
This information has been left in for historical purposes but should not be acted upon.
Niello-engraving
A kind of engraving of considerable antiquity. It was very much practised in the middle ages. The art consisted in drawing a design with a stylus or needle on gold and silver plates, and then cutting it with a graver. These incised lines were then filled with a composition of copper 1, bismuth 1, lead 1, and silver 9, the compound being of a bluish color when a little sulphur is added. The metal is called Niello-silver, or Tula. Nitre, or Saltpetre, as it is commonly called, occurs as a native product in the earth in many parts of the world, and is separated therefrom by leaching the soil and allowing the nitre to crystallize. It is artificially formed by heaping up organic matter with lime, ashes, and soil, and keeping the mass moistened with urine for a lengthened period, when the heap is lixiviated and the salt crystallized out. Nitre dissolves in about three times its weight of cold and one third its weight of boiling water. Paper dipped in this solution and dried forms what is known as touch-paper. Nitre has a cooling, saline taste, and strong antiseptic powers. Owing to the latter quality it is extensively used in packing meat. It is chiefly consumed, however, in the manufacture of gunpowder; the large amount of oxygen it contains, and the feeble affinity by which it is held, adapting it for sudden and rapid combustion.