A new process of working pearl-shell into a variety of devices, for the purpose of applying it to ornamental uses in the manufacture of japan ware and other articles, has lately been invented by Messrs. Aaron Jennings, and John Betteridge, of Birmingham. The process is similar to that of engraving on metals in relief, by the aid of corrosive acids and the etching-point. The pearl-shell is first divided into very thin plates or leaves, such as form the 40th to the 100th part of an inch, and the devices or patterns are drawn upon them in an opaque turpentine varnish; strong nitrous acid is then brushed over the plates repeatedly, until those parts left bare, or undefended by the varnish, are sufficiently corroded, or "eaten away " by the acid. The varnish being now washed off by a little oil of turpentine, the device, which the acid has not touched, is found to be perfectly executed. If the design is to be after the manner of common etching on copper, then the process upon the shell is precisely similar to that already explained under the article Engraving. When a considerable number of ornaments are required of the same size and pattern, a sufficient number of the plates are cemented together by glue, with only one plate, having the device etched upon it, placed on the outside; these are then made fast in a pair of clams, or screwed between the jaws of a vice, and carefully sawn out altogether by a very fine frame-saw: the cemented shells are then thrown into warm water, which softens the glue, and quickly separates the pieces.
When several devices upon a plate have been bit in, they may be laid upon a flat surface, and cut through with a knife-edged tool; for thick pieces the saw is put in requisition, and the finishing executed by a variety of sharp gravers and instruments.