This principle was first explained by Professor Cowper, of King's College,
In addition to Cameo Incrustation which was patented many years since, a subsequent patent was secured for taking fac-similes of casts or dies from intaglios, and impressing them upon hollow Glass vessels in intaglio. This plan of Glass engraving has been chiefly adopted where numerous copies of elaborate devices have been required; such as badges of regiments, or arms upon decanters and table Glass. The following is the mode of operating: dust Tripoli, very finely pulverized upon the die or cast; then a larger coating of dry plaster of Paris and pulverized brick-dust, with another layer of coarser plaster of Paris and brick-dust; place the whole under a press, which when screwed to its utmost, allow waters to saturate
[The above represents the workman
fitting the cold, dried, Tripoli-faced plaster cake, into the recess of
the mould, as it occasionally requires a little reducing with a file.
It is afterwards removed, and brought to a red heat in a small muffle
set in the furnace, and placed in the heated brass mould with a pair of