NRLC

Publications
 
 
 
Method for conservation of high lead bronzes

Lead has customarily been added to bronzes to increase the fluidity of the molten metal for the ease of casting. Lead is not completely miscible with copper above 6 to 8 %, and , on cooling, excess of lead is segregated as globules in high lead bronzes. As such lead is highly susceptible to atmospheric corrosion and corrodes preferentially in the presence of copper. Corrosion of lead present as globules on or near the surface of the object may give rise to unsightly pits on them. Recurrence of the white powder in the pits after cleaning strongly suggest the selective corrosion of lead. In case of smaller objects like coins a white substance may leach when the objects are dipped in water for cleaning. To prevent such type of corrosion,.

The results of the studies have been published in Studies in Conservation, 48, 203-209 (2003).

 
Method For Treatment of 'Bronze Disease'
How Zinc Dust Works?

Zinc in presence of water reacts with chlorides of cuprous chloride to form zinc hydroxy chloride, and cuprous chloride is converted into cuprous oxide. The zinc hydroxy chloride is a highly insoluble crystalline compound, formed through a series of complex reactions. First, the zinc hydroxy chloride is crystallised in irregularly thin but relatively extensive plates and acts as a moisture barrier. As more chlorides become available, dense hexagonal plates of 4Zn(OH)2.ZnCl2 are formed on standing. These plates are tough and impervious to moisture and act as a seal, and, therefore, in absence of moisture further deterioration process stops. If any chloride diffuses from underneath and reaches the seal, the excess zinc present in the seal will react with it and the quality of the seal will further improve.

The results of the studies have been published in the Studies in Conservation, 40, 110-119 (1995).

 
bronze  |  copper  |  iron  |  dyes
RTI ACT