COATING AND COATINGS

Lack of colour permanence can also be associated with less contemporary finishes. A few years ago, a leading chemical manufacturing concern built a spacious office block in Victoria Street, Westminster. Much thought was given to the choice of windows. A final touch of luxury was imparted to the façade by the selection of lightly toned bronze windows; this is a Victorian touch of splendour normally associated with banks, consulates and similar establishments. The term ‘bronze’, in the window trade, assumes a breadth of definition remarkable for even such an ill‐defined term, and is extended to beta brasses. However, the windows were installed, lacquered and admired by all. A few weeks later, a darkening of colour became apparent. This was investigated, attributed to the formation of copper sulphide as a result of permeability of the lacquer film to atmospheric contaminants, and the frames were cleaned down, repolished and relacquered using a competitive brand. The lacquer was applied by spray—the weather was hot, but with gusts of wind, and the comments elicited from the occupants and passers‐by were practically sufficient to induce some colour change. However, the task was completed, and in due course the phenomenon recurred, but more severely. A third attempt gave no better results, and an acceptable degree of permanence was achieved only when the windows were painted with a bronze paint, which consisted of aluminium powder in a tinted vehicle.