Restoration of ancient bronze bells: Part II: welding
There is a big number of church bells from 16th to 19th centuries in the highlands of Northern Chile, which are damaged by use during centuries and by falls due to earthquakes that affect the region. Some of them are cracked or have lost some of their parts. The aim of this work was to use an efficient welding method to repair the pieces lacking some of their parts, leaving a minimum trace of repair and extending their useful life. Restoration of a bell with smelting defects, lacking some parts, is described. The first method employed was an alloy similar to that of the piece under study, which eliminated the issue of material incompatibility between the filler and the bell. In order to do this, X-ray fluorescence was used to analyze a part of the repair zone. With data obtained from analysis, smelted bars were used for welding and plates of equivalent geometry were used to replace the missing parts. The second method used was commercial silver-tin alloy welding with flux coating. In both cases, results indicated a good joint, however, in the second case cost is higher and the color results make restoration evident. Both of the alloy restorations remained in a phase, which is ductile and has no aging problems. Ultrasonography and penetrant liquids detected no cracks. A significant number of valuable colonial bells, now damaged and out of service, restoration is justified. They must be preserved, since they are a valuable part of the nation's cultural heritage.