COLCOTHAR OF VITRIOL, see Oxide of Iron.
COPPERSMITH'S WORK, subsequently to its having been annealed for the last time, and before it is planished with the hammer, is generally pickled with sulphuric acid and water, in about equal parts, and scoured with coarse red tripoli and water, to remove the oxidation caused by the fire. The work when planished is cleaned, 1st, with crocus and oil, 2ndly, the oil is rubbed off with whiting, and 3rdly, the work is polished with dry crocus, the rubber being generally an old worsted stocking.
COQUILLA NUT receives a good natural polish by the following applications: - 1st, glass paper; 2ndly, tripoli and oil on rag; 3rdly, dry putty powder or rottenstone. This routine gives a more durable polish than hardwood lacker applied with friction, a mode of finish also employed.
Common turned and filed works are often finished with one or two coats of varnish, applied like paint with a brush, this gives them a coarse brightness.
Eccentric turned works in coquilla nut are polished very slightly with putty powder or rottenstone and oil on a brush; but the tools should be very sharp, so as to leave but little or no necessity for polishing at all.
CORAL. - The red variety of this singular substance is somewhat used in jewellery, and admits of an excellent polish. When in rounded pieces, it is polished after the routine followed by the lapidary with Alabaster; when coral is cut in facets as for beads, etc, it is worked like Carnelian.
COROSOS or the vegetable ivory nut, see vol. 1, page 112, is polished just the same as the ivory of the elephant, and other animals; but the vegetable ivory, apparently from its facility of absorbing moisture, alters sensibly in size and form during the process of polishing.
CROCUS. See Oxide of Iron.
CUTLER'S GREEN HONE, see Hone Slates, article 6.
DEVONSHIRE OILSTONE, see Hone Slates.
DUTCH RUSH, or the Equisetum Hyemale, is said to be a native of Scotland, and to thrive best in the marshy places in mountainous districts; it is gathered in pieces two or three feet long, which are intersected by knots at distances of four to six inches. The rush is usually of the size of a writing quill, of a greenish-grey colour, with a groovy surface that feels rough like fine glass paper, from the quantity of silex disseminated throughout its exterior surface, and upon which circumstance depends its suitability to polishing hardwoods, alabaster, marbles, and some other substances. According to the analysis of Sprengel, Dutch Rush, when dry, contains rather more than 13 per cent. of ashes, viz. Silex, 6.38, Carb. Lime, 5.51, Potash salts, .79, and Alumina .46.
For the application of Dutch Rush, see Wood, article 5, and Alabaster, article 1.