When speaking in another part of this work about the methods of conferring an appearance of age to newly cast bronze, we remarked that the faker’s best accomplice in the ageing process was chemistry. The colouring and bronzing of metals in fact is usually accomplished by one of two methods, by the action of chemicals or by the application of bronze powders rendered impalpable and used as a pigment.
The latter method is mostly used in modern industrial art, but has, nevertheless, been applied in imitating antiques and in disguising mended parts, etc. It is often used with success in the case of imitations of excavated objects which generally have a bluish-green patina. This may be imitated to deceive the eye of the beginner only, by the application of green-bronze lacquer of a dull lustre, or of green varnish. The green of the bronze colour is best prepared by mixing Frankfort black with chrome yellow.
These are, however, but cheap and not always convincing expedients, the real way to give tone and colour to bronze and other metals is by resort to chemistry.
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.