Low-melting alloy metals of two or more metals selected from the group consisting of bismuth (Bi), lead (Pb), tin (Sn) and cadmium (Cd), have been known for many years. Of particular interest here, and, known heretofore, are such alloy metals having a melting point below 350.degree.F.
An especially interesting example of such alloy metals, commonly called Wood's metal, consists of 50 parts Bi, 25 parts Pb, 12.5 parts Sn and 12.5 parts Cd. This metal and other alloy metals of these components can have especially low melting points, as, for example, melting points below 200.degree.F.
These low-melting metals have recently found increasing use for making jewelry and other decorative items. Articles fashioned from the metals generally have a bright "silver" appearance.
The prior art suggests that to obtain a dark oxidized silver appearance on articles made from low-melting metals that a mixture of black and raw umber paints be applied as a thin coating and partially rubbed off, or be selectively touched into recessed areas of the article (School Arts, February 1970). This prior art method, however, does not provide an ideally authentic appearing dark oxidized silver patina.
Heretofore, the prior art has provided methods for imparting to high melting metals the appearance of the dark oxidized silver patina characteristic of "antique silver." See, for example, U.S. Pat. No. 3,767,475. In addition, copper solutions have been used to color high-melting metals. See, for example, U.S. Pat. Nos. 2,519,672 and 3,615,747.
It would be desirable to impart an authentic appearing dark oxidized silver patina to articles made from low-melting alloy metals in order to provide "antique silver" articles fashioned from low-melting alloy metals.
USPTO Backgrounds
USPTO Backgrounds