A brown colour on bronze, for instance, may be obtained by preparing a sand bath large enough to contain the article to be bronzed. When the object has been cleansed from all grease by dipping in boiling potash lye, it is treated with white vinegar. After this preliminary operation the object is wiped thoroughly dry and then rubbed with a linen rag moistened with hydrochloric acid. When this coating is perfectly dry--a quarter of an hour is sufficient--the article must be heated in the sand bath until it has acquired a bluish tint, and a final rubbing with a linen rag soaked in olive oil will change the blue colour to brown. Recipes and processes are endless and so rich in hues that almost any tone may be obtained. To any interested in this branch of imitating old metals we can but suggest the excellent book, _The Metal Worker’s Handy Book_, edited by William T. Brannt. As we have said, there are many methods by which to give the proper patina to metals, and a good deal of mystery, some fakers and imitators claiming to be in possession of unrevealed secrets. When exposed to the air for a long time, copper and bronze acquire a fine brown or green patina which, as every collector knows, greatly enhances the merits of an artistic piece in these two metals. A perfect imitation of the result of a long process of time is not an easy matter, in fact an almost impossible task. Formerly the patina of a bronze was in a way the final test of authenticity, but nowadays there are modern imitations of so deceptive a character that the best connoisseurs are taken in. One of the best known methods by which old patina is imitated on copper and bronze, is to follow as closely as possible the process by which the genuine patina is produced. Thus the action of rain, interment, immersion in some permeating substance that will generate hydrosulphuric acid are called into service by those willing to wait a comparatively long time for the desired effects. Others accelerate the above process by increasing the proportion of the natural conducive elements. The objects are also treated with water containing ammonia, carbonic acid, etc., exposed to the intense and direct action of vapour or vaporized acid in order to produce those basic salts that form a certain patina. To obtain the malachite kind of patina that generally characterizes objects found in the ground, the imitator generally brushes the metal over with a very weak solution of cupric nitrate to which a small quantity of common salt in solution may be added. When completely dry it is again brushed over with a liquid consisting of one hundred parts of weak vinegar, five of sal-ammoniac and one of oxalic acid, and the application is repeated after the first has dried. In about a week’s time the metal will have acquired a green-brown colour that may be polished with encaustic if the patina is to have a shiny appearance.