Mother-of-pearl can be obtained prepared for use in various qualities and colours, blue, pink and green being the most expensive. It can be cut with a jeweller's piercing saw and filed to shape, but should be backed with a temporary veneer or sheet of paper before cutting as some varieties are very brittle. If laid with hide glue it should be roughened with a file and any slight curvature taken up with plaster of Paris mixed in the glue. Very little pressure must be used, sufficient only to press the shell home flush with the surface, and final finishing is done with 10:0 grit abrasive paper, from which the fierceness of the cut has been knocked off by rubbing two sheets together, followed up by pumice powder and rottenstone. The pearl can be engraved by brushing over with warm wax, scratching through the wax when cold and pouring nitric acid into the scratches, after which mastic suitably coloured is run into the lines to complete the design. Tortoiseshell can be cut and laid in a similar fashion to pearl, and can be cleaned off by scraping and papering and then polishing with dry whiting or rottenstone. It is usual to colour the ground under the shell, or insert gold-foil underneath to increase the brilliance. Ivory is obtainable in fairly large pieces and can be turned, cut and shaped with normal woodworking tools, laid with normal glues and the surfaces flushed off with scraper and file followed up with fine paper and pumice powder, and polished with whiting on a chamois-leather buff. Bone and horn are fair substitutes in small sections but lack the wonderful depth and ripple of real ivory, while white plastics are only poor imitations, although valid materials in their own right if treated as such.
Was this article helpful?
THIS book is one of the series of Handbooks on industrial subjects being published by the Popular Mechanics Company. Like Popular Mechanics Magazine, and like the other books in this series, it is written so you can understand it. The purpose of Popular Mechanics Handbooks is to supply a growing demand for high-class, up-to-date and accurate text-books, suitable for home study as well as for class use, on all mechanical subjects. The textand illustrations, in each instance, have been prepared expressly for this series by well known experts, and revised by the editor of Popular Mechanics.